UC-NRL B 3 mi ering Molded Electrical Insulation and Plastics By EMILE HEMMING New York WARD CLAUSEN CO., PUBLISHERS 200 FIFTH AVENUE 1914 COPYRIGHT 1914 BY EMILE HEMMING ALL RIGHTS RESERVED Tk 3 Engineering^ Library TABLE OF CONTENTS Introduction 5 What Is Molded Insulation? 7 Molded Insulation Ten Years Ago 9 Classification of Molded Insulation Used To-day 16 Raw Materials, etc 20 Hot Molded Organic Materials (Class ' 'A") . . 66 Cold Molded Organic Materials (Class ' 'B") . . 71 Cold Molded Inorganic Materials (Class ' !..'.- .They have a considerable advantage over the copal resins in that they ,dp not have to-.be distilled to render Jthem suitable for the manufacture of . varnishes and other compounds used in the preparation of Binders ^employed RAW MATERIALS 41 in the manufacture of molded insulation, as they fuse or melt readily when subjected to heat. SHELLAC The story of the production of shellac is perhaps more interesting than that of any other material used in the manufacture of molded insulation. Lac is a vegetable substance as it is the sap of a tree, but it is also an animal product in that it is exuded by an insect. These insects (the coccus lacca, carteria lacca, etc.) infest several species of trees growing in India and southern Asia, notably certain varieties of fig trees. The female produces the lac to protect her eggs. This insect, after attaching itself to the plant, remains fixed there and proceeds to extract the resinous sap and to convert it into lac, with which she incrusts herself and in which she deposits her eggs. In a short time, the eggs burst into life, and the young, which are very minute, eat their way through the dead bodies of their parents, and swarm all over the twig or small young branch of the tree in such countless numbers as to .give it the appearance of being covered with a blood-red, dust. ..,,,,. ,, ,,,,,. : ,,The method of preparing the lac for market is crude but effective:. TJie .incrusted twigs, when broken from the, trees, are known as .sticji. lac. The brittle lac is readily removed Jrpm the sticks .by nieans of rollers. The crude lac, which ^s, of a -:, ,; "-..T-:, :-; ii'VsW' , i 1 RESINS DAMMAR GUM This variety of resin is obtained from the amboyna pine and comes principally from Java and Sumatra. It 46 MOLDED INSULATION exudes sap naturally like the spruce and other members of the pine family, but this yield is increased by making incisions in excrescences which grow on the trunk of the tree. It is also gathered in considerable quantities from the beds of streams flowing through the districts in which the tree is found. It comes to the market in small, usually transparent, homogeneous, lumps. Its principal use in insulating manufacture is in binders for the hot molded organic materials (Class "A"). It begins to melt at 80 deg. C., and at 100-deg. C. it commences to flow rapidly. It does not melt as readily as rosin, but more readily than other resins of the copal series. It is soluble in benzole, turpentine, and ether with- out the application of heat. It is also soluble in benzine, in which it differs from most other resins. Although affected by atmospheric exposure, it is much more stable under these influences than rosin and is much to be preferred to it, and would supersede this gum entirely were it not for its higher cost. ROSIN The term, rosin, is applied to the residue obtained from the distillation of the resinous exudation of various species of the pine tree, the volatile portion which dis- tills over being turpentine. It is found in the market in hard, homogeneous masses and varies greatly in quality. The quality depends upon the percentage of turpentine distilled off as well as upon the quality of the resinous exudation from which it was derived. In color, it varies from a light, transparent, RAW MATERIALS 47 yellow amber to almost black. It is quite hard and very brittle and softens readily under heat at 75 C., becoming a thin liquid at about 100 C., above which temperature it decomposes. It has the property of becoming a limpid liquid at comparatively low temperatures, which makes it so use- ful a substitute for shellac in the organic cold molded materials. It is not much used in the manufacture of electrical insulation, except for this purpose, but finds manifold uses in various of the liberal arts. The use of rosin* in the manufacture of molded in- sulation should be discouraged, since its cheapness is its only recommendation. Many attempts have been made to render it more heat-proof and to give it a more stable nature, but while much literature has been pub- lished on this subject, very little practical result has been attained. PARAFIN WAX This term is applied to a variety of hydrocarbons of the paraffin series, obtained ffom shale oils. It is a solid softening readily at 50-deg. C., and was formerly used for impregnating electrical insulation materials. But owing to its low melting point it is but very little used for such purposes to-day. The reason it retains its place among the substances in use for the manufacture of electrical insulating ma- terials is that it will withstand the action of alkalies better than any other organic insulating substance. It is also un- affected by strong acids at ordinary temperatures. 48 MOLDED INSULATION LINSEED OIL This oil is obtained by pressing the seeds of the flax plant. According to the character of the seeds and the method of extraction employed, the oil Varies from a pale, tasteless, product to 'an amber or yellowish colored, limpid, liquid of characteristic taste. It is of incalculable value in the electrical arts and is extensively employed in conjunction with resins and as- phalts for the manufacture of varnishes and impregnating compounds. In such preparations, 'it acts not only as a solvent, but due to the fact that it absorbs oxygen from the air, it has an oxydizing effect upon the resinous and asphaltic bodies with which it is mixed. This is par- ticularly true of the boiled linseed oil, which will continue to increase in weight by the absorption of oxygen from the air until it becomes viscous or even hard. In practice, this drying or oxygen absorbing property is increased or hastened by the addition of metallic oxydizing agents. Linseed oil is used not only in combination with other substances, but the boiled oil itself, without other ad- mixtures, except, perhaps, driers, is used to a considerable extent for impregnating and coating clothes and tapes as well as for treating molded insulation and insulating parts. A number of methods have been proposed and con- siderable patent literature is available relating to the production of solid resinous products from linseed oil which might be substituted for shellac asphalts or resins in the manufacture of molded insulation. The object of these experiments was to take advantage of the high heat-resisting properties of the resinified linoxen pro- ducts in the manufacture of such materials as those of Class "A'" (the organic hot molded materials), but no RAW MATERIALS . 49 great success has been attained in this direction, partly owing to the fact that one of the chief advantages of employing shellac and similar binders for materials of this class lies in their property of becoming plastic under heat during the molding process, and the linoxen products are far less plastic than shellac and consequently are not so easily molded. On the other hand, considerable success has attended the compounding of linoxen products with rubber and as- phalts to produce rubber substitutes which are success- fully employed in the manufacture of molded insulation. Another interesting application of linseed oil which has been proposed, consists in heating cellulous, starch, refuse horn, hoof by-products, and other materials, with linseed oil to a temperature beyond the point of decomposition, at which temperature the components were supposed to react upon each other to form a new resinous substance. Unfortunately, beyond laboratory experiment and elaborate patent literature, nothing noteworthy was de- veloped. Owing to its high price, linseed oil is subject to much adulteration and replacement by rosin oil, mineral oils, and other cheaper oils, and, while it is often difficult to detect the presence of such adulterants analytically, their imperfect drying and poor elastic qualities soon proclaim them in practice. VARIOUS OTHER DRYING OILS Besides linseed oils, there are a few other oils used in connection with the utilization of resins and asphalts for insulating purposes. 50 MOLDED INSULATION Among such the following are worthy of mention : Chinese wood oil or Tung oil: This oil is obtained from the seeds of the Ying tzu tung, a tree indigenous to China, and is used in very considerable quantities as a substitute for linseed oil. This product exhibits one marked difference from linseed oil in that it dries at a uniform rate throughout its mass, whereas the latter dries from the surface inward. Soja bean oil : Obtained from the fruit of the Soja bean tree. Poppy seed oil: Obtained from the plant Papaver Somniferum. Rosin oil: Obtained from the dry distillation of rosin. This oil, owing to its low price, is a common adulterant of linseed oil. Its drying qualities are not equal to those of linseed oil and it is of such an un- stable nature as to make its use inadvisable for elec- trical insulating purposes. MINERAL OIL SOLVENTS Various derivatives distilled from petroleum and coal- tar at different temperatures are employed in the manu- facture of liquid compounds of resins and asphalts. They are usually cheaper than the drying oils and do not dry, or rather evaporate readily, which is a source of frequent complaint from users of these liquid solutions or compounds. They are employed in the manufacture of impregnat- ing compounds and cheap insulating varnishes, as well as for impregnating insulating cloths and tapes. Their evaporative qualities vary greatly. Some will dry or evaporate on exposure to the atmosphere, while RAW MATERIALS 51 others require considerable heat. This variation renders them applicable to a wide range of purposes. TURPENTINE This well-known solvent is obtained from the dis- tillation of the exudations from various species of the pine tree. It is the volatile product of the distilling pro- cess, the residue being rosin. It is much valued for its use in connection with dis- solving waxes, resins, and similar materials used for electrical insulating purposes. When exposed to the air, it dries slowly but steadily by absorbing oxygen. The major part of it evaporates, leaving a minor part of resinous hard substance behind. In this respect of drying by absorption of oxygen, turpentines differ from other solvents, such as naphtha, benzol, etc., as these latter solvents evaporate rapidly and leave no residue behind. BENZINES Benzene obtained from the distillation of coal-tar, and the benzine or benzoline obtained from the distilla- tion of petroleum oils, are both widely used as quick vola- tile solvents for asphalts, resins, and copal oil compounds, because of their excellent dissolving properties and vola- tile characteristics. ALCOHOLS Among the alcohols ethyl or grain alcohol and methyl or wood alcohol are both used to a considerable extent for dissolving the resinous organic binders in the manu- facture of insulation products. 52 MOLDED INSULATION They are principally used to dissolve shellac and other alcohol soluble gums. Such solutions are also of great importance in the manufacture of built up mica and quick drying shellac gum varnishes. CAOUTCHOUC OR CRUDE RUBBER This is the name given to the product of the milky latex which exudes from incisions made in tlie bark of certain trees found in tropical and semi-tropical countries. While ' many trees produce this latex to a greater or lesser degree, there are certain regions which, in the quality and quantity of this product, surpass all others. At the present time the rubber trees found in the Amazon District of South America give a latex which in purity and quantity surpasses any now known. Generally speak- ing the world's supply of crude rubber comes from Central America. South America, Africa, and Asia. The quality of the rubber is rated in the order named. While the methods of handling are different in the various districts, the ultimate result is the collection of the milk or latex found in the bark of the trees, and the reducing of it by certain processes to the commodity known as crude rubber. The latex consists of rubber, resins, and other organic substances, and water. In the Hevea plant, which is considered one of the best of the Amazon trees, only 30% to 32% of the latex is rubber. In other trees the percentage is even less. Crude Rubber contains more or less foreign matter according to the manner in which it is collected. In the Amazon District care is taken to prevent the latex from coming in contact with alien matter with the result that the loss due to this cause is verv small. The RAW MATERIALS 53 African and Asiatic trees are carelessly cut and handled, often permitting the flowing latex to drip down the sides of the trees to the ground with the Vesult that stones, earth, leaves, etc., are collected with it. The loss from such careless methods is often as much as sixty per- cent. The consumption of rubber is steadily increasing and new uses are being found for it every day. Conse- quently the supply of crude rubber is naturally one to be looked to with some concern. The likelihood of an inadequate supply before many years and the constantly increasing price of crude rubber has resulted in the plant- ing of rubber trees in the districts where these trees are found in their native state. The rubber obtained from such cultivated trees is known as "PLANTATION" Rub- ber and is usually of a higher grade than the wild rubber. Rubber in its crude state is very seldom used com- mercially as it is very susceptible to atmospheric changes. At a temperature of 51.7 deg. C. it becomes very sticky and has great adhesiveness, while at deg. C., it is very hard and brittle and is easily broken. To over- come these faults the process known as vulcanization is resorted to, the principle of which is the incorporation of sulphur in some form and the subsequent heating of the mixture. The sulphur in general use for vulcaniza- tion is in the form of flowers of sulphur. This form of sulphur has a specific gravity of 2.00 and in good com- mercial form is of a bright, lemon color. It is insoluble in water and alcohol and mixes readily with crude rub- ber. In mixing the sulphur with the rubber care is taken to thoroughly incorporate it by running the two materials together through iron rollers which are so geared as to travel at different speeds, which in so doing not only press the materials thoroughly together, but 54 MOLDED INSULATION also exert a pulling stress upon the mass. Crude rubber when properly mixed with sulphur and vulcanized under- goes changes in both its physical and chemical properties. It is not then affected by ordinary changes of tempera- ture. Its elasticity is greatly increased, and it is not soluble to any great extent in such agents as naphtha or chloroform, which, before the admixture, readily reduced it to a liquid solution. There are a number of methods of vulcanizing rub- ber, the principal one being known as the steam process. In this process the steam may come in direct contact with the mass held in a large cylinder or tank, or the heat of the steam may be exerted on the outside of a mold which holds the rubber mass, this mass having no contact with the steam itself. Before being subjected to the heat the sulphur, to the amount of from 3% to 60%, is thoroughly mixed with the crude rubber. As sulphur fuses at about 113 deg. C., it is necessary to subject the sulphur impregnated rubber to a heat of at least this temperature. It has been found by experiment that when such rubber is subjected to a temperature of over 150 deg. C., for any length of time, the mass shows a tendency to carbonize and harden. So for all practical purposes the temperatures are kept between 130 deg. and 140 deg. C. relying on the length of time to produce the de- sired hardness or density in the finished article. In the manufacture of hard rubber the mass is sometimes vul- canized at a temperature of 160 C. for six or seven hours. In the manufacture of rubber goods, the purposes for which the article is intended must be taken into con- sideration. Where soft, pure rubber would work to ad- vantage in one place, it would prove a failure in another. It can be readily seen that while a pure, elastic, rubber RAW MATERIALS 55 stock would act to advantage in flexible insulating tubes, the same stock would prove a disadvantage in the mold- ing of solid insulators. Consequently, certain chemicals and minerals in addition to the variable proportions of sulphur are incorporated with the crude rubber, this admixture depending upon the purpose for which it is to be used. When the finished article is intended to resist heat. as for electric insulation, minerals which are known to possess heat-resisting qualities, such as asbestos or other inorganic fillers, are added in greater or lesser quanti- ties. Hard rubber or ebonite is prepared in practically the same way as vulcanized rubber. Sulphur to the amount of 30% and sometimes over 50% is added to the crude rubber and it is subjected to a temperature of over 150 deg. C. for several hours. As an electrical insulator, rubber must be rated highly. It has been found that rubber in its unvulcanized state has a higher dielectric strength than after being vulcanized and that compounding with chemicals and minerals decreases this property in proportion to the percentage of chemicals and minerals used. Inasmuch as sulphur is also a good insulator, crude rubber, mixed with sulphur alone, is sometimes used for electrical work, but on account of the cost of the rubber compounding to the extent of 50% to 90% is often resorted to. While many substitutes for rubber have been offered, they lack the excellent toughness and elasticity which rubber possesses and till these substitutes can be pro- duced possessing these qualities and at a lower cost than rubber, the latter will continue to hold its own. Vast amounts of money and effort have been ex- 56 MOLDED INSULATION pended throughout the civilized world in attempts to produce rubber by artificial means and it seems as if at last success was in sight. These efforts have for some time past centered on the cheap production of isoprene, the essential constituent of India rubber. The new process from which so much is expected, is based on using starch as an initial raw material, pro- ducing therefrom amylalcohol by a process of fermenta- tion and converting the amylalcohol by certain chemical manipulations into the unsaturated hydrocarbon isoprene. Isoprene had previously been produced from various s'ubstances, such as from turpentine, acetylene, and ethylene, but due to the high and fluctuating cost of these materials, the production of synthetic rubber had not made any remarkable progress until the discovery of a method of deriving isoprene from so simple, cheap, and readily obtainable a material as starch. Isoprene when properly treated will polymerize into rubber. . The process here referred to is comparatively new and it is too soon to make positive predictions as to the success of this very interesting development in this im- portant art, but the future of a process depending on so cheap and simple a raw material is full of promise and it looks as if the goal for which so many investiga- tors have so tirelessly striven is at last almost attained. FORMALDEHYDE Formaldehyde (Methylaldehyde, or Methanal) H.COH is the oxydation product of Methylalcohol CH 3 OH and the Aldehvde of Formic-acid HCOOH It is the RAW MATERIALS 57 simplest type of all Aldehydes, the latter being the oxyda- tion products of the primary alcohols. This may be shown in the following schemes : /H 2 7 H R,C< R.C/ X OH X Prim. Alcohol Aldehyde /H, /O H.0< H.C< x OH X H Methylalcohol Formaldehyde "R" Indicating any organic radical or element what- ever. Though Formaldehyde was discovered as early as 1867, and although its important functions in the process of assimilation in plant life has been recognized by prominent chemists for many years, its technical use and manufacture on a large scale dates back only to about 1886. Formaldehyde at ordinary temperatures is a gas of pungent smell, which at 21-deg. C. condenses to a color- less liquid. In commerce, it usually occurs in a watery solution of about 35% to 40%, which is known under the technical term of " FORMALIN," or in its polymerized and solid forms as the so-called "PARAFORM" (HCHO) 2 or as "TRIOXYMETLIYLENE (HCHO) 3 . Formalin, however, is the usual commercial form of Formaldehyde. By the incomplete oxydation of methylalcohol, the latter being mixed with air, in the presence of any contact substance (catalyser) usually granulated copper, Form- aldehyde is produced as an intermediate product between methylalcohol on the one hand and formic acid on the other hand. This process formulated in the equation: CH a OH+O=HCOH+H 2 58 MOLDED INSULATION is at the present time the usual way of manufacturing- Formalin. On further oxydation Formaldehyde yields formic- acid and finally carbonic-acid: HCOH+0=HCOOH HCOOH+0=CO 2 +H 2 b The oxydation with copper as a catalyser starts at a temperature below 300-deg. C. By carefully watching the temperature and not allowing it to rise too far above 300-deg. C., the quantity of carbonic acid produced will be negligible. The methylalcohol present in excess in the watery Formaldehyde solution is separated from the latter by fractional distillation in column dephlegmators. The aqueous formaldehyde solution of commerce, however, contains about 10% of methylalcohol, which prevents the polymerization of the formaldehyde. Formalin, like the gaseous formaldehyde, has a pun- gent odor and shows frequently a slightly acid reaction due to the formation of traces of HCOOH. The specific gravity of formalin of the usual commercial strength of 35-^0%, is 1.081 to 1.097. A. few other processes of more scientific interest may be briefly mentioned here. If a mixture of methan CH 4 with a quantity of air insufficient for a complete oxydation, is passed over glowing copper or asbestos, formaldehyde is produced. Formic acid is transformed into formaldehyde by mixing the acid vapors with hydrogen and passing this mixture over iron, nickel, zinc or other metals, at high temperatures. By evaporating an aqueous solution of formaldehyde, paraformaldehyde (HCOH) 2 is produced as a white am- orphous mass, which on drying passes into the other modi- RAW MATERIALS 59 fication, trioxymethylene (HCOH) 3 . This body is volatile at 180 200-deg. C. turning into formaldehyde again. Formaldehyde, as the first and lowest type of the aldehydes possesses an enormous capability to undergo reactions with other compounds, even with such compara- tively indifferent bodies as kerosene oil or benzol. Formaldehyde precipitates mercury and bismuth in alkaline solution. It reduces silver even in its insoluble chloride, and silver mirrors are made by the action of gaseous ammonia upon a paste of silversalt formalin. With ammonia and formaldehyde hexamethylene- tetra-amine C H 12 N 4 is formed. When boiled with lime- water it yields formic-acid and an amorphous saccharine substance methyl enitan. Its condensing reactions are very numerous, and it is chiefly due to this circumstance that its technical application has increased so enormously within the last twenty years. Formaldehyde condenses with dimethylamin into tetramethyl-diamidodiphenylmethan, the raw material of the leuko-base of Krystallviolet. Also other dyestuffs like parafuchsin, rieufuchsin, etc., are made by means of formaldehyde. Besides its use as a disinfecting material instead of phenol and mercury bichloride, it finds a large applica- tion as a preservative for crude, raw products, in tan- neries, soap works, etc. It is often added to glues, gums, or starch solutions for a similar purpose. Its applications in many industries, such as in photog- raphy, leather making, and in the manufacture of india rubber goods, etc., are very great. It condenses with phenols producing resin-like bodies, which, besides being the raw materials of many substitutes for amber, hard rubber, bone, etc., have proved to be substances of high 60 MOLDED INSULATION insulating power, wherefore, this condensation reaction of formaldehyde with phenols will be treated in this book in a special chapter under "CLASS 'G.' " PHENOL Phenol is the type of a series of organic compounds which form a class by themselves as derivatives of the so-called aromatic compounds, the latter having as their representatives benzene or benzol. As the chemical structure of both bodies readily shows, phenol results theoretically from the substitu- tion of one H-atom in the benzol nucleus through the hydroxyl or OH group this radical being the typical chemical characteristic of all phenols. "Whereas phenol itself, as the first representative of the phenol group, contains only one OH radical, it is possible to substitute gradually all 6 H-atoms in the benzol nucleus, thus arriving at higher phenols. Since the H-atom of the phenol OH group, is of a more electro-negative character than the hydrogene of the alcohol-OH group, we. may consider the phenols as a group, standing between, the alcohols and the acids. This explains the term carbolic acid used sometimes in- stead of the more scientific name "PHENOL." Phenol, discovered in 1834 by Runge, occurs very widely in the animal, as well as vegetable kingdom. As a product of the change of matter in the human and animal body it occurs in the urine. Furthermore, phenol or its homologues, is formed by the decay of albumin, ty rosin and the like, and especially by the destructive distillation of organic compounds, as, for instance, wood and bones, also by the dry distillation of bituminous and RAW MATERIALS 61 anthracite coal. It occurs in the needles and sap of -pine wood, in mineral oils, and is technically one of the most important constituents of coal tar, the latter being the main source of its manufacture. Although synthetic methods of manufacturing phenol are well known, its production from coal tar is still the most usual and economical way. As the phenol is soluble in caustic alkali, it can easily be isolated from coal tar by agitating the latter in the solutions of the former. Acids will then separate the free phenol from the solution,. The phenol itself is then puri- fied by fractional distillation. The chemical part of this comparatively simple pro- cess is shown by the equations : C H 5 OII+NaOH:=C 6 H 5 ONa+H 2 2C H 5 ONa-fH 2 S0 4 =2C H 5 OH+Na 2 S0 4 Phenol is also soluble in concentrated sulphuric acid, thus forming sulphonic acid. Due to this reaction, practical manufacturing pro- cesses have been introduced to separate phenol from the tar oils ; although their yield is not quite as satisfactory as that produced by the alkali method. Of the synthetic processes of producing phenol, two may be mentioned on account of their greater importance in the art. They are the methods of Griess, and Kekule, Wurtz and Dusart. Griess produced phenol on a large scale by boiling the diazocompound of aniline diluted acids. Kekule, Wurtz, and Dusart have found independently of each other, that benzolsulphonic acid is turned into phenol and potassium-bisulphite by fusing it with 62 MOLDED INSULATION potassium hydroxyd, the chemical reaction being as fol lows: C H 5 SO s Na+NaOH=C e H 5 pNa4-NaHS0 3 This synthesis especially was successfully applied for some time when the market price of phenol was high enough to permit it. The resulting phenol showed a remarkable purity and a somewhat weaker and more pleasant odor. But as the same result is now obtained in a cheaper way by the production of phenol from coal tar, as mentioned above, the synthetic methods are nowadays almost entirely abandoned. In a pure state, phenol crystallizes in long white needles, which melt at 42.2-deg. C., and boil without be- ing decomposed at 183 184-deg. C. Ordinary phenol, however, melts somewhat lower, usually at 35.5 40.5-deg. C., due to traces of cresol or water. The specific gravity of phenol at 18-deg. C., is 1.065. Owing to its hygroscopic qualities, phenol exposed to moist air, takes up a considerable amount of water and the melting point is lowered. Though hygroscopic, phenol itself is not very readily soluble in water, one part of phenol dissolving in 20 parts of water at ordinary temperatures. Other solvents like alcohol, ether, benzol, glacial acetic acid and glycerine, on the other hand, dissolve phenol in all pro- portions. Phenol can be extracted from its watery solution with benzol, ether, carbon disulphide or chloroform. The watery solution does not redden litmus. Phenol has a peculiar smokelike smell, it attacks the skin very violently and is poisonous in its internal effects, due to its property of coagulating albumin. Of its many characteristic reactions the more im- portant ones may be mentioned. RAW MATERIALS 63 Ferichloride, not in excess, gives a violet color with one part of phenol solution to 3,000 parts of water. Twenty cc of a solution of phenol to 5,000 parts of II 2 O show on gradual heating with ammonia and Eau De Javelle, a deep blue color, which is changed by the action of acid, to red. Phenol, added to a solution of nitrous acid in sul- phuric acid, gives gradually a brown, then a golden, and finally a blue color. Another very important reaction of phenol consists in its behavior when treated with bromine water. A watery solution of phenol, with a freshly prepared solu- tion of bromine water, gives a bulky, white, precipitate, even in solutions up to 1 : 40000 or 50000. Upon this reaction a quantitative method of determining phenol is based. The reaction of phenol with formaldehyde and its different modifications are of very great interest and the resulting products will be dealt with in further articles under "Condensation" and "Synthetic Resinous Pro- ducts" (Class G). CONDENSATION Condensation is a special form of the many synthet- ical reactions applied in organic chemistry. The simplest form of a condensation takes place when two molecules of the same or different organic compounds unite under proper conditions by means of carbon linkings, whereby one or more molecules of water are eliminated, and a more complicated compound of a higher carbon content is formed. This newly formed body is termed a condensation product, and it is usually 64 MOLDED INSULATION impossible to decompose it into its original components. Generally some condensing agents, as for instance H 2 SO 4 , ZnCl 2 , anhydrides, caustic alkalies, ammonia and its de- rivatives, which are capable of splitting off H 2 0, are ap- plied, thus causing the condensation reaction whereby one of the substances loses oxygen, whereas the other one splits off hydrogen as shown in the equation. CH 3 CHO+CH 3 CHO=CH 3 CH :CH.CHO-f H 2 Acetaldehyde Acetaldehyde Crotonaldehyde Water Sometimes, however, morfi than two molecules of the same or different substances may combine, with separation of H 2 O. C 6 PT 5 CHO-f2C 6 H 5 NH 2 = C 6 H 5 CH (C 6 H 4 NH 2 ) 2 +H 2 Benzaldeliyde Aniline Diamidotriphenylmethan Water In other condensations, elimination of HC1; NH 3 or even C(X may take place. To the latter reaction belongs the well-known process of producing Ketones by heating calcium salts of organic acids. (CH 3 COO) 2 Ca=CH 3 COCH 3 +CaCo 3 Calcium Acetate Acetone Calcium Carbonate Also by means of an oxydation a condensation re- action may be produced. Phenols containing one OH group, for instance, when treated with ferric chloride, lose one atom of hydrogen and turn into higher phenols containing two OH groups and the double amount of carbon atoms: 2C 10 H 7 OH+2FeCl 3 =C 20 H 12 (OH) 2 +2HCl+2FeCl 2 Naphthol Dinaphthol Aldehydes and especially ketones are very liable to condensation reactions, whereby complicated compounds of very high molecular weights are frequently produced. The same process we probably encounter, according to more recent discoveries, in the formation of resins in RAW MATERIALS 65 plant life, the latter being very likely condensation pro- ducts of formaldehyde with phenol. 66 MOLDED INSULATION THE HOT MOLDED ORGANIC MATERIALS (Class "A") The ingredients of sealing wax and of this class of molded insulation have not varied from their earliest history. The binders play the important part in this class of materials, the principal ingredient of which once was, and still ought to be, shellac. Owing, however, to the steady increase in the price of shellac, it has been replaced almost entirely by cheaper materials, such as damar gum, rosin, asphalts, pitches and cheap resins. Two methods are employed to combine these binders with such fillers as wood pulp, magnesia, lime, sand and asbestos, and such coloring matters as lamp black, various metallic or earth pigments, and organic dye stuffs. First : The organic binders are placed in a heated mixing machine in which they are melted, and when in a molten condition, the binders are gradually added and mixed. The mixture is then removed in a hot plastic condition and rolled into sheets. These sheets are broken into convenient sizes, softened on steam tables and then placed in heated dies, pressed, cooled therein, and re- moved in a finished condition. The dies in this method are the open dies, described more fully under the chapter 11 Moulds and Dies." In the second method employed in molding this class of products the organic binding materials are dis- HOT MOLDED ORGANIC MATERIALS 67 solved in proper solvents and the mass mixed with the filler in about the same kind of mixing machines as in the first method, except that no heat is employed. The material is removed from the mixing machine and on exposure to the air the solvents evaporate, leaving an intimate, uniform, mixture. This mass having become hard is ground to powder. The powder is then placed in heated dies in which it remains under pressure until it is melted, it is then cooled and removed from the die in a finished condition. The dies used in this method are called "closed dies." This type of die is explained under the chapter "Molds and Dies." Manufacturers of products of this class vary the minor details of the processes of manufacture, but all follow one of the two above mentioned fundamental methods. Materials produced by either of these two methods differ but little in their properties. The second method, however, allows the incorporation of more filling ma- terial. In the first method, the amount of filler which can be added is restricted, for if too much is used, the plastic nature of the mix is diminished and the material will not flow properly in the die. The second method is free from this difficulty, for the material, being in a powdered form, can be readily in- troduced into the dies, which are of such design that the material cannot ^escape, but is forced to all parts of the die, and intimately welded together by the pressure. The higher the proportion of binding material, and the more finely reduced the filler, the more plastic the mix will be, and the cleaner the .appearance of the finished piece. 68 MOLDED INSULATION On the other hand, the higher the percentage of filler, especially when the filler is inorganic, the less plastic the mix will be and the poorer the appearance of the finished piece, but it will be less subject to the softening influence of heat, which constitutes a serious defect in materials of this class. The composition of material of this class varies over a wide range, and the characteristics differ accordingly. If the binder is entirely free from rosin or cheap gums, these products are very stable and their life is long. Unfortunately, however, the general trend for the past ten years has been to substitute rosin and dammar gum for shellac, which, especially in case of rosin, due to its well-known unstable qualities, will cause the compound to deteriorate rapidly under climatic exposure. However, rosin is extensively used because of its low price, and the advantage it possesses of being rapidly melted and molded at comparatively low temperatures. in which respect it is the best substitute for shellac. All other substitutes have the objection of requiring higher temperature to melt, and not being so readily molded in dies. It should be stated here that a certain variety of bitumens or asphalts melt very easily, but pieces made with such binders do not withstand any great tempera- ture. In some cases, these products have been known to soften under the rays of the sun. Materials of this class, when proper ingredients are employed, are practically non-hygroscopic, and moisture has no detrimental effect on their physical or chemical properties. It might be mentioned that products of this class, containing a great excess of fillers, for in- stance, asbestos fibre, will absorb more or less water, but these products, if properly made, even though they HOT MOLDED ORGANIC MATERIALS 69 absorb moisture to a certain extent, are sufficiently im- pervious under ordinary weather conditions for use for ordinary voltages, if they contain no rosin. As none of the ingredients undergo any chemical change in the processes employed in the manufacture of these products, it is perfectly obvious that they will always soften at the temperature to which they are subjected in their mixing or molding processes. For instance, articles made with shellac, which softens at 80 C., will not withstand temperatures above this point. Kosins, which stand less, and materials made with soft bitumens, will soften in the sun's rays in hot weather. This is particularly true if the binders are in great excess in the mixture. Such materials can be made so that they will with- stand a momentary flame, and if not subjected to heat for too long a time, they will not readily soften, but they will invariably fail as soon as a continuously ap- plied temperature reaches the melting point of the bind- ing medium. The insulating properties of this class of materials vary very materially. For instance, one specimen .001 inch thick may be punctured by 500 volts, while another specimen of the same thickness will be punctured by 50 volts. The reason for this great difference lies in the wide variation in the composition of materials of similar ap- pearance. The higher the percentage of organic binder, the better the insulating properties; the lower the percentage of binder, and the higher the percentage of filler, the poorer the insulating qualities will be. The more intimate the mixture between the filler and binder and the higher the pressure under which it is molded in the proper plastic condition, the less porous the product 70 MOLDED INSULATION will be, and consequently the higher its resistance to puncture. The use of such materials for electrical insulation has somewhat diminished because these products do not withstand heat. They are liable to become inflamed by the short circuiting of wires carrying low voltages, and the Underwriters are steadily becoming more and more strict and are specifying materials of greater heat-resisting qualities. The field, however, for this class of materials is still very large, and from the following illustrations, it will be seen to what a wide range of uses in the elec- trical art, these materials are still adapted. Several concerns, both here and abroad, have, after long study and experiments, been able to produce pieces suitable for high tension insulation, and they claim considerable advantages for these substances over por- celain for high tension work. The discussion of insulation for high tension work is not within the province of this work, and therefore these special shellac com- pounds will not be treated here in detail. It may be said in passing, however, that this material has been com- mercially produced for this purpose, although the bulk of insulation of this kind is still made in porcelain. COLD MOLDED ORGANIC MATERIALS 3 71 COLD MOLDED ORGANIC MATERIALS (Class "B") Molded insulating products of this class are similar in appearance to those of Class "A," and chemical analysis would show that they are composed of an organic binder and an inorganic filler, as are most of the materials of that class. The usual binders employed in the manufacture of these products are the asphalts, and the fillers are such inorganic substances as asbestos, silica, and magnesia, organic fillers being but rarely employed. In color they are universally black, due to the asphalts used in their composition. A fundamental and very important difference be- tween materials of this class and those of Class "A" is that the incorporation of the filler with the binder and the subsequent molding is not done under heat, but the binding medium is brought into solution by suitable solvents, and the filler thoroughly mixed with the liquid or semi-liquid binders in a cold condition. This semi- plastic mixture is then molded in cold dies, care being required to have the material sufficiently soft to mold properly. The pressed pieces are then subjected to a drying process, during which the solvents are drawn off or enter into composition with the other constituents, whereby a hard, solid and durable substance is obtained. The making of materials by this process presents some manufacturing disadvantages, for instance, during the drying process, they are subject to a slight shrink- 72 MOLDED INSULATION age, unlike articles molded of the materials of Classes "A" and "G," which come from the dies in a finished condition. For this reason a slight variation of the finished pieces, from exact dimensions, should always be allowed as is customary with users of porcelain. How- ever, as the shrinkage incident to the drying of these materials is only one-eighth that which takes place in the firing of the ceramic products (porcelain) they can be depended upon for greater degree of accuracy than those of Class "D." In fact, the art of manufacturing these cold molded inorganic materials has undergone such development dur- ing the last ten years as to make it entirely practicable to mold such materials with sufficient accuracy to fully meet the demands of commercial conditions. The products of this class are not manufactured in such a great variety of grades as those of Class "A" and while the insulating properties of different materials of this class vary, their use is, as yet, restricted to the manufacture of parts for low tension insulation. One of the chief advantages of these products and one to which is due their wide favor among electrical engineers is that they are exceedingly stable, and once manufactured will not soften under heat, and moisture has little effect upon their physical or electrical properties. In Class "A" it is the binder which is always the im- portant part, whereas in materials of Class "B" it is the filler the asbestos fibre which imparts to the pro- duct its main advantages, the binder performing the functions of cementing and waterproofing media. COLD MOLDED INORGANIC MATERIALS 73 THE COLD MOLDED INORGANIC MATERIALS (Class "-C") Materials of this class differ from those of Class "A" and "B" in the characteristic principle of the use of an inorganic binder, while in Classes "A" and "B" an organic binding media is used. The binders of this class are compounds of silica, alumina, lime and magnesia, or usually Portland Cement, while the filler is usually asbestos fibre. The use of hydraulic cements for such purposes was retarded for years, due to its poor plasticity, but during the last ten years great progress has been made in this direction, and today they are extensively used as binders for materials of this class. Its use as a binder is, however, a critical one, and not only must the cement be selected with great care to assure its fitness, but in the manufacturing operation several well defined steps are necessary in order to obtain a properly plastic material. The main difficulties consist in the proper incorpora- tion of reagents to develop the plasticity of the mixture without injury to same. Their action is yet not thorough- ly understood, but possibly it is of a catalytic nature. Broadly speaking, the binder is incorporated with the filler in the presence of water, and the moist mixture is pressed in a cold state in dies under heavy pressure, whereby the excess of water is eliminated and the molded pieces are given a consistency which permits them to 74 MOLDED INSULATION be removed from the dies. The hardening of the mold- ings afterwards is effected by the action of the hydraulic binders in a similar way to the hardening of Portland Cement. Such insulating products, owing to the inorganic nature of both binder and fillers, are unaffected by heat and the electric arc, and by various treatments they are rendered non-absorbent to moisture. The appearance of materials of this class is not as attractive as that of materials of Classes "A," "B," "G" and "E," but their physical properties, owing to the nature of the inorganic binder, possess the peculiar ad- vantages of rather improving in quality with age, as do all materials of concrete nature containing hydraulic binding media. Both binders and fillers play an equally important part in the compounding, and the mechanical properties of the finished articles depend to a considerable degree on the structure of 1 the asbestos fibre used as a filler. CERAMICS 75 CERAMICS (Class "D") This class is usually known under the broad term of "CERAMICS," the most familiar representative being porcelain. Other materials of this class are glass, fused silica, fused clay and roasted soapstone (Lavite). PORCELAIN The so-called hard porcelain is of the most impor- tance for electrical uses. Hard porcelain comprises a large percentage of China Clay, to which is added quartz and feldspar or other flux, and sometimes small percentages of gypsum, chalk, etc. The quality of the China Clay used, is of first importance, for on this is dependent the plasticity of the mixture, which enables it to be molded in the desired forms, and also, to a large extent, the final hardness, strength and heat-resist- ing qualities of the product. The proportions in which these ingredients are used vary with different manufac- turers, each of whom has developed a formula by which proper results can be. obtained. Great care is necessary in each step of the manufacturing process, from the mixing of the ingredients to the annealing of the products as they come from the kiln. A slight relaxation of care at any one stage is more likely to endanger the quality of por- celain than of other molded insulating products. In the manufacture of porcelain the various raw 76 MOLDED INSULATION materials in proper proportion are mixed in rotating drums in the form of a slurry, it being, of course, essential that the ingredients be in a finely divided form, and in the case of the China Clay, free from impurities. The excess water is removed by various means, and the wet mass is stored for some time, during which the homo- geneity and plasticity are improved. In some plants this plastic cake is directly molded in dies, while in others it is dried, re-ground, mixed with water and molded. In pressing porcelain pieces, more especially when the walls are thin, great care is necessary. The articles, after drying, are burned in kilns at various temperatures up to 2,000-deg. C. The temperatures and methods of firing vary with different manufacturers, and great skill has been developed at this stage. Owing to the considerable shrinkage of porcelain in the firing process, it is evident that wide practical knowledge of the behavior of various shapes in the kiln is essential in order that the final product shall be of the form and dimensions originally designed, and it is worthy of remark that this art has undergone such development as to enable the production of parts of very complicated design. LAVA COMPOSITION In making articles of this substance, the waste from the cutting up of slate is used. The powdered material is mixed with solutions of sodium silicate. The mass is dried, powdered, and molded in dies under pressure after the addition of sufficient water. The molded articles are then fired at high temperatures, and after cooling are again treated with the alkaline silicate solution and CERAMICS 77 fired again. This operation is repeated until absorption of the alkaline silicate ceases. The finished products are very hard and tough and are somewhat similar to porcelain. They resist sudden changes in heat better than porcelain and for certain insulating purposes are, therefore, more desirable. Their great shrinkage during firing and the consequent diffi- culty in obtaining accuracy in the finished molded form. is their principal draw-back. Special grades of lava compositions are made for resistance insulators and for this purpose have no superior. 78 MOLDED INSULATION RUBBER COMPOUNDS (Class "E") Among the various materials employed in the manu- facture of Molded Insulation, rubber is the only product which in itself, without the admixture of a filling or strengthening medium, presents all the desirable quali- ties of an insulator, combined with the necessary mechanical strength and other requisite physical prop- erties. Its toughness, elasticity and flexibility are not even nearly approached by any other insulating substance know T n today. Therefore, its qualifications as a binder for organic or inorganic fillers are also unsurpassed. The only reason why this excellent insulation as well as binder has been gradually replaced is its high price and inability to stand continuous temperatures of 100-deg. C., or over, even when properly compounded with such heat-resisting fillers as asbestos. In the chapter on raw materials will be found a full description of the preparation of caoutchouc, and rubber and their compounding. ORGANIC PLASTICS 79 ORGANIC PLASTICS (Class "F") CELLULOID While molded insulating parts are not made of this material to any notable extent, it is nevertheless em- ployed for this purpose, especially where ornamental ap- pearance is a considerable factor. It is a good insulator and can be molded with greater facility than perhaps any other material, and were it not for its poor heat- resisting qualities, it would be extensively employed for electrical insulating purposes. Celluloid is a solid solution of more or less nitrated pure cellulose in camphor, and is pressed, after evaporat- ing the various solvents in the form of sheets, plates, blocks or rods. In this stage it is a transparent, elastic, flexible mass which can be given any desired color by the introduction of dye stuffs or pigments. Before going into the details of the manufacture of celluloid, the manner of making nitro-cellulose and the general method of making celluloid will be briefly outlined. Nitrocelluloses are celluloses which contain the nitro group N0 2 , and are known as Di, Tri, etc., up to hexamitrocellulose or even higher ones, according to their content of the nitro groups. In celluloid manufac- ture, as a rule, the higher nitrated celluloses are used, commonly known as "gun cotton" which contain about 9% to 12% nitrogen. 80 .MOLDED INSULATION They are obtained by treating very pure cellulose, like tissue paper, purified cotton, flax or hemp fibres, with a mixture of concentrated nitric acid and more or less concentrated sulphuric acid. The proportions of the two acids may be varied considerably. For instance, three volumes of nitric acid Spec. Grav. 1.517, to one of sulf. acid Spec. Grav. 1.84, or three volumes of sulf. acid Spec. Grav. 1.845, to one of nitric acid 1.5, are used. The proportions of the paper and of the acid mixtures vary considerably. Furthermore, a different time of re- action has to be allowed according to different con- ditions. The space in this book is too limited to go into these complicated details. The nitrocellulose, purified by washing with cold water until perfectly free of acid, is then treated with a weak sodium carbonate solution at ordinary tempera- ture, and the latter again removed by washing with cold water. The pure material is ground to pulp, the water extracted in centrifuges, and after having been dried at about 40-deg. C. it is mixed with a solution of camphor in alcohol. The proportion of camphor and nitro-cellulose varies from 20% to 30% of camphor and 70% to 80% of nitro- cellulose. The alcoholic camphor mixture is passed between rollers heated to 105-deg. C. This process is carried on until a homogeneous and plastic mass results. These rolled celluloid sheets are then pressed into solid blocks, free of air bubbles, under a pressure of about 3,500-lbs. per square inch. A few of the special methods employed in the manu- facture of celluloid may be mentioned. 1. The so-called Hyatt process consists in dissolving ORGANIC PLASTICS 81 gun-cotton in molten camphor. Satin paper is sprayed with a mixture of two parts nitric acid and five parts sulphuric acid as it is unwound from a roll, whereby the greater part of the paper is converted into nitro- cellulose or pyroxylin. The acid is now entirely removed by washing with water, and the plastic mass is subjected to considerable pressure and dried. The lumps, after being broken up again and drained in a hydroextractor, are ground and finally mixed with the camphor in the proportion of one part of camphor to two parts of pyroxylin, though other proportions also give good results. The well mixed mass is then pressed in order to expel any watery constituents still present; and further- more, to bring the particles of camphor and pyroxylin into still more intimate contact to facilitate the solvent action of the former. The dried and pressed mass is placed in molds and given the desired shape by the application of hydraulic pressure, under heat. On leaving the press, the celluloid is hard, but remains plastic and can be re-softened by warmth, or by placing it in boiling water. 2. Cold process of preparing celluloid. In operating this process, the greatest care must be taken on account of the great inflammability and low boiling point (35-deg. C) of the ether which is used to dissolve the camphor; thorough ventilation of the fac- tory rooms is very essential. The proportions used in this method are 50 pounds of nitro-cellulose, suffused with a mixture of 100-parts of ether. After the ether has been slowly evaporated, the mixture finally becomes a transparent, sticky, gelatinous mass, which is rolled between a pair of superimposed calendering rollers until it is plastic. On exposure to the air, the rolled viscid 82 MOLDED INSULATION sheets attain a certain hardness. They are then warmed and subjected to powerful pressure. This is important as the valuable properties of celluloid are improved in proportion to the pressure applied. To obtain good celluloid by the cold ether process it is also highly important that the raw material should be dry and per- fectly free from acid, otherwise the celluloid will be cloudy. In another process, the gun cotton after being pulped with water, is treated with a mixture of camphor and woodspirit (methylalcohol). The principle, however, is identical with that of the other process. Pure celluloid is nearly colorless. In thin sheets it is as clear as common glass. It is very elastic, trans- parent, tough, and hard. Celluloid has a faint smell of camphor which becomes stronger when the mass is rubbed. It is electrified by friction. Heated sufficiently it be- comes plastic and can be molded into any shape desired. On heating up to 140-deg. C., celluloid loses its color and transparency, and at about 50-deg. higher decomposes Avith the liberation of pungent, readily inflammable vapors. Since celluloid softens in warm water the molding process is greatly facilitated by this behavior. Celluloid ignites only when brought in direct contact with flame and then burns with a smoky flame giving off an odor of camphor. On blowing out the flame the mass con- tinues to flow and to give off thick fumes of camphor. This is a clear proof that celluloid is not a chemical combination of camphor and gun cotton, since it is char- acteristic of chemical reactions that the substances enter- ing into combination cease to exist independently in the compound. Celluloid is insoluble in water and though not im- ORGANIC PLASTICS 83 mediately attacked by concentrated sulphuric acid it gradually dissolves therein. A small piece entirely dis- appears in about 36 hours. Concentrated nitric and boiling caustic alkali also gradually dissolve it. The specific gravity of celluloid varies according to the degree of pressure to which it has been subjected in the manufacture, the mean being 1.50. Celluloid is very extensively used as a substitute for horn, tortoise shell, coral, malachite, lapis, marble, ebony, amber, caoutchouc, ebonite, etc. As a matter of fact, there is hardly any natural product which has not been imitated in celluloid. Continuous experimenting and research is carried on in attempts to render celluloid less inflammable and to make it more useful as an electrical insulator. ALBUMINOIDS CASEIN The purpose of the creation of these products was to obtain a substitute for celluloid which would not have the poor heat-proof characteristics of the latter. Pro- ducts of extraordinarily fine nature have been developed, based on treating curdled milk with acetic acid or other reagents to throw down the casein. A plastic mass is thus obtained to .which organic or inorganic filling material is usually added. It is then molded in heated dies in a manner similar to the ma- terials of Class "A." Such products would not be stable under the action of moisture, but treatment with formaldehyde renders this mass less susceptible to humidity and other climatic influences. These compounds can be easily worked with tools and stand temperatures of 20-deg. to 30-deg. higher than the 84 MOLDED INSULATION celluloid compounds. They char upon the application of heat without inflaming. This material will, however, not stand the continued action of water as well as the celluloid compounds, but its higher heat-resisting and non-inflammable qualities render it valuable for many purposes. As insulating products, these materials are not to be considered of great importance, their use being practically confined to the manufacture of molded articles for domestic use. In all such compounds, the casein plays the important part, but numerous inventions have lately been developed to partly substitute the casein by organic or synthetic resinous binding products. While these newer compounds may improve the quali- ties of this product, they have not yet produced materials of any great value for electrical molded insulating parts, notwithstanding their excellent plastic qualities. SYNTHETIC RESINOUS MATERIALS 85 SYNTHETIC RESINOUS MATERIALS (Class "G") In discussing the hot molded organic products (Class "A"), attention has been called to their most serious defect, namely; their low-melting point due to this characteristic of their chief binding medium, namely shellac. The replacing of shellac by a binding medium having all the valuable qualities of this material without its serious defect of softening at comparatively low tempera- tures, has been highly desirable. The serious interference with the proper and reliable operation of electrical apparatus and machinery caused by the softening or inflaming of the molded insulating parts made of materials of Class "A" has caused elec- trical engineers and designers to eagerly seek a more heat and fire resisting product. The materials of Class "G," the Phenol-Formalde- hyde products, have all the advantages of the hot molded organic materials (Class "A") and in addition possess heat-resisting qualities to a high degree and are well suited for every purpose to which these Class "A" ma- terials are adapted. Unfortunately, their high manufac- turing cost restricts their use very largely to articles of electrical insulation, the cost of which is of little consideration or a small item in the cost of the apparatus. The peculiar heat-resisting and dielectric properties of these products are due to the binder, a synthetic 86 MOLDED INSULATION resinous substance obtained by the chemical reaction of phenol on formaldehyde. As early as 1872, such artificial resins were obtained and at various times since considerable literature has been published and much research work undertaken in endeavors to produce such synthetic resinous substances on a practical commercial basis. It seems strange that while today the high heat- resisting properties of these products are recognized as a vital characteristic advantage, the earlier investiga- tors and inventors had nothing further in mind than to produce synthetically what nature had already given in shellac. The research work done along this line consisted in combining phenol with formaldehyde by means of heat, with or without the presence of acid or alkaline agents, to act as catalysers, causing the mixture to condense. The water is thus eliminated by evaporation, or it is otherwise separated from the viscous, condensation product. Various proportions of the constituent materials, the kind of catalytic agents used, the length of time of heating and temperatures, all affect the character of the resulting compound, which is first a viscous liquid and then a hard, fusible solid, which on further heating, poly- merizes into an infusible product. Up to about six years ago, such synthetic resinous bodies were not valued for their heat-resisting qualities, that is, their characteristic of becoming an infusible sub- stance upon the further application of heat; and they were of no great value as shellac substitutes in the literal significance of the term substitute, because of their higher cost. Consequently, they were not much heard of outside the laboratory and in patent literature. SYNTHETIC RESINOUS MATERIALS 87 The brittleness of the final hard product was another reason why their usefulness was so long unrecognized, but by incorporating fibrous substances with these syn- thetic resinous materials a product was obtained. Molded articles made from this equal or surpass in strength every known insulating material, with the exception of rubber products. While the production of these phenol-formaldehyde compounds has reached a state of perfection which may reasonably be termed a scientific as well as a commercial success, very little is known of their exact chemical com- position. Attempts have been made to show a definite chemical reaction and a definite atomic combination be- tween the constituent elements, but the various authors of such formulae and theories disagree to such an extent that we must conclude that the exact nature of this substance has not yet been determined, and await further investigation to give us more conclusive scientific in- formation. The commercial molded insulating products of this class and the methods employed to incorporate with them the organic or inorganic fibrous filling materials, will now be discussed. One manner in which this is accomplished is by heating the mass obtained by the condensation process only to a point where it is plastic when hot, but hard when cold. In this stage of its production, it is ground to powder and mixed in suitable proportions with the fillers. This mixture is placed in heated dies and held' under pressure until the binder is first rendered plastic and then transformed into the hard infusible state. The dies are then cooled sufficiently to permit the removal of the molded pieces. Such pieces leave the dies in a finished state exactly as the shellac compounds do. 88 MOLDED INSULATION Generally, these pieces on the application of a flame, give off a carbolic acid odor. Some manufacturers try to overcome this by subjecting the pieces to a further exposure to heat, to drive off these odors. Another method of producing molded articles of this class is to mix the viscous, condensation mass directly with the fillers, heating the mixture just to a sufficient degree to make it hard when cold, but plastic when hot, grinding it to a powder and subjecting this powder to the same treatment as described above. It is therefore seen that the mixing in of the filling materials and the molding of the compound must be done before the binder reaches its infusible state. There are at the present day a great many patents covering the manufacture of these synthetic binders, but they are all based on the principle here mentioned. Two distinct products of the above type are now made for electrical purposes with considerable success. While the manufacturers claim marked differences in their products, the characteristics of the binders are the same, and any difference which exists is dependent upon the character of the fillers. One product is obtained by using a filler which is chiefly an organic material (wood pulp), while the other employs asbestos fibre. The products made with wood pulp have the ad- vantage of being more easily molded and leaving the dies with a more elegant appearance, but while those made with asbestos fibre are in this respect somewhat inferior, they resist heat better, noticeably the electric arc. The manufacturers using wood pulp claim that their product is heat-proof to 175-deg. C. ; the manufacturers using asbestos claim 250-deg. C. The difference in the heat-resisting properties of these two products is in no SYNTHETIC RESINOUS MATERIALS 89 way dependent on the binders, it depends entirely on the filler. In the case of the product made with the organic filler, the comparatively low heat-proof quality is due to the nature of the filling material, while the breakdown point of the material made with the asbestos filler is the limit of heat-resistance of the binder. Both products are claimed to be unaffected by moisture or water. Exposure of several years has confirmed this ; but this class of synthetic binders is of too recent introduc- tion to make a definite statement as to their water-resist- ing qualities in comparison with such organic binders as rubber. The writer has made various tests on both these pro- ducts, and has found that both materials, if properly manufactured, are practically unaffected by moisture ; but the wood-pulp material after an immersion of several months in water seemed to be slightly more affected than the materials with the inorganic filler. As in the case of the shellac compounds, the more inorganic filler used the more such material will with- stand arcing; the more binder used, the easier these pieces are molded and the less they absorb moisture. The insulating qualities of these phenol-formaldehyde products are very high, and they have found a ready market. Another advantage they possess is that they can be molded into any shape with absolute accuracy. 90 MOLDED INSULATION FIBRE (Class "H") Under this heading we will discuss those materials which have been known under this name from the earliest times, and also a newer fibre product which is cemented by means of resinous binders. VULCANIZED FIBRE This material is prepared by treating vegetable fibres (paper) with chloride of zinc or other metallic chlorides, alkaline compounds, and sulphuric acid. The fibres are thus partly dissolved and brought to a somew r hat sticky (glutinous) condition in which they are subjected to high pressure, generally in the form of sheets of various thickness. The action of the various active chemical compounds used in the treatment of the fibre, and the pressure after- wards used, render the product homogeneous and tough; but as the rinsing out of the excess of the various chemi- cals is never complete, the remaining portions are the source of the troubles so often experienced in the use of this material for electrical insulating purposes. Vulcanized fibre is unaffected by organic solvents. It is very tough and its property of being easily worked with tools has made it an extensively used product in electrical work. FIBRE 91 It does not burn immediately on exposure to a flame or arc, but will char and carry the flame after a few moments exposure to heat exceeding 175-deg. C. It is unstable under atmospheric exposure, and warps and deforms readily. This inability to resist water is the most serious drawback to this product. FIBRE TREATED WITH RESINOUS BINDERS This class of materials has come into favor lately with electrical engineers, for it has the excellent prop- erties of fibre without the drawbacks of the latter 's unstable nature. These materials are manufactured by agglomerating fibres by means of dissolved resinous substances (such as shellac or copal solutions) or by phenol formaldehyde binders. The so agglomerated fibrous sheets are then sub- jected to pressure under heat in a manner similar to the manufacture of built-up mica, the heat causing the binder to melt and thus to cement the fibrous layers firmly together. This class of material, when made with synthetic resinous binders, is very stable and exhibits high dielec- tric and heat-proof qualities and good mechanical prop- erties. "When the binders are of a natural resinous nature, the heat-resisting properties are governed by the soften- ing point of the binder. 92 MOLDED INSULATION MOLDED MICA (Class "I") These products are made by splitting mica into thin laminae which are cemented together by means of resin- ous binders. The so built up sheets or forms are afterwards sub- jected to pressure and heat, the heat melting the bind- ing materials, thus forming a compact product. Accord- ing to the nature and proportion of the binders used, these mica compositions can be made more or less heat- resisting, but obviously to such a degree only as the binding material will withstand. All attempts so far to cement mica in sheets or in powdered form by means of an inorganic binder have failed, but should these attempts ever prove successful, a very broad field will be opened up for this excellent insulating material. PROPERTIES 93 PROPERTIES LIFE The first requirement of a molded insulating part is that it be stable. That is, it must retain its shape and physical and electrical characteristics under service. It must not deform nor disintegrate, and it must main- tain its dielectric strength. Neither heat, cold, nor sudden temperature changes, the action of the electrical current, nor chemical actions induced by this current, must exert any deleterious effect upon it. No material in use today perfectly fulfills all of these conditions. The materials which most nearly meet these require- ments are the ceramics, Class "D." The inorganic compounds, "Class "C," are also very stable. This class possesses the peculiar characteristic of improving with age and exposure to air and weather, in which important particular it differs from porcelain, (which is inert under these conditions) and all other forms of molded insulating material which deteriorate more or less with age. The bituminous, cold molded materials, Class "B," while they do not meet these requirements as fully as the two foregoing classes, are still very durable ; for, during the higher temperature treatment to which they are sub- 94 MOLDED INSULATION jected after molding, the unstable elements are either driven off or forced into stable combinations and ren- dered inert. The rubber compounds, Class "E": Rubber when properly compounded is very stable, but unfortunately the increasingly high cost of the better grades of this valuable substance offers great temptation to the manu- facturer and practically all commercial rubber is adul- terated with low grade resinous gums and other sub- stitutes which greatly reduce its life and consequently its usefulness as a material for molded insulating parts. The synthetic resinous compounds form a new class of peculiar products which have been in use for a com- paratively short period and definite judgment must be withheld until time has demonstrated their value. The writer has seen this material in service both outdoors and indoors, where it has seemed to fulfil all the claims of its adherents, but knows also of cases where in outdoor work it has not given satisfaction, although this may have been due to faulty or careless manufacture and not to any inherent defect in the material. It is the writer's opinion that the very broad claims made for it are not extravagant, and that it will before long be so fully developed as to wholly justify itself. The shellac compounds Class "A" suffer un- der the same disadvantages as the rubber materials. High grade shellac compounds are quite stable, but as shellac is comparatively expensive, most of the materials of this class are adulterated, usually with rosin, which in consequence of its unstable nature, and very low melting point, very seriously affects the value of materials of this type. Class "F" The celluloid compounds are stable at PROPERTIES 95 low temperatures, but due to their poor heat-resisting qualities their use is restricted. The albuminoids are quite stable under certain con- ditions, but in consequence of their very hygroscopic nature they are unsuited for molded insulation. Class "H" Fibre Ordinary Fibre is falling into disrepute because its shape changes with varying atmos- pheric conditions. On the other hand, the new class of hardened veget- able fibre is of a stable nature. It is practically unaf- fected by climatic conditions, although its use is not ad- vised for outdoor insulating work. Owing to the hygro- scopic nature of organic fibres, a certain amount of moisture is absorbed. It will, however, retain its shape. MOLDING Another fundamental requirement of a molded in- sulating material is that it may be readily formed into such shapes as the requirements of the particular use to which it is to be put demand. The methods employed in the manufacture of molded insulation can be broadly separated into two fundamental classes the cold molding process and the hot molding process. In the first class the material is molded in cold dies and subjected to a further process after pressing. In the second class, the material is first rendered plastic by heat and then molded in hot dies, the articles being removed from the dies when cold in a finished state without subsequent treatment. The first method is employed for the materials of Classes "B," "C" and "G." 96 MOLDED INSULATION The second method is employed for the materials of Classes "A," "E," "F" and "G." The materials made up by the second method can b'e molded into almost any shape that may be required and with great accuracy, as these materials when molded are perfect plastics, and leave the dies in a finished con- dition. The fact that the materials made by the first method have to be treated after pressing has been responsible for a great deal of inaccuracy of dimensions in cold molded insulating parts. The materials used in the first method are, generally speaking, not so easily molded into com- plicated shapes, nor with such a nice degree of accuracy, but considerable progress has been made in the last few years in this particular branch of insulating manufacture, and parts can now be obtained which meet all reasonable requirements. Attention shquld be called here to the peculiarity of the materials of Class "B" not being suitable for molding into flat plates or parts of large size. On the other hand, the materials of Class "C," are particularly adapt- able for such purposes. Materials in Class "D" are liable to a shrinkage as high as 15% in their subsequent treatment (firing). This makes it difficult to control with accuracy the dimensions of the finished piece, and it has become a custom of the trade using porcelain to allow a variation of .015 per inch or more in parts made of this material. Some manufacturers of materials of Classes "B" and "C". claim that they can mold true to size, while others require the acceptance of a variation not exceeding .010 of an inch, especially in pieces of complicated form, but it would be advisable for designers of parts to be made of cold molded materials to bear in mind that all such PROPERTIES 97 materials are apt to vary slightly from the drawings and not to originate such combinations of insulating material and metallic parts as may be unfavorably af- fected by a variation of a few thousandths of an inch. For pieces in which no variations can be allowed and where extreme accuracy and perfect finish are re- quired, materials of classes "A," "E," or "G" are to be preferred, provided other conditions permit their use. Practically all molded insulating materials except those of Class "D" can be manufactured with metal parts imbedded in them. The practice of molding in metal parts has become very extensive and has been a large factor in the suc- cessful introduction of molded insulation, as it has elimi- nated the process of inserting these parts in the shop, which process is often expensive and unsatisfactory. On the other hand, such excellent results have been obtained by this process of incorporating metallic in- serts in molded parts that some designers have become over enthusiastic in regard to this feature, and expect too much of the molded insulation manufacturers, espe- cially in pieces of complicated design, and they would do well when designing new combinations to consult with the manufacturer from whom they expect to pur- chase before going too far with their specifications and drawings. The materials of Class "H" are not strictly molded materials, but are furnished in sheets, tubes and rods. PUNCTURE TEST The insulating value of molded materials is usually determined by puncture tests. 98 MOLDED INSULATION As this treatise will not discuss insulation for high tension work, and has only to consider voltages below one thousand, the materials of all the different classes herein enumerated can be considered as chosen for the particular conditions, and the thickness of the insulating part is designed to correspond to the insulating properties of the material selected. The insulating properties of porcelain or other cer- amics vary according to the properties of the chemical components of the product. The insulating properties of the cold molded inor- ganic materials Class "C" vary not only according to their composition, but to the treatment they receive in the various stages of their manufacture. Class "B" In the cold molded organic materials, the mixture again plays an important part, but the amount of pressure and conditions under which the piece is subjected to this pressure determine to a very great extent the nature and value of these products. Classes "A" and "E" The Shellac and Rubber Compounds. The variation in the insulating properties of these materials depends almost entirely on the com- pounding of the products. The amount of pressure employed in molding is not of great importance, provided sufficient pressure is used to thoroughly weld the ingredients. Class "F" The organic plastics are uniformly of high dielectric strength. They are dense, homogeneous masses composed of ingredients of high insulating value and contain no fillers to render them porous, or to reduce by their lower insulating value the point at which these materials puncture. PROPERTIES 99 Class "G"- The synthetic resinous materials vary in dielectric strength somewhat according to the nature of the synthetic binder. These binders as produced today do not differ greatly from each other in respect to their dielectric strength, hence, the value of materials made with them as the important ingredient, depends princi- pally upon the nature of the fillers entering into their manufacture. Class "H" Fibre like the organic plastics is of a homogeneous nature and its insulating value doe not vary greatly, but is somewhat dependent upon the physi- cal treatment and seasoning it undergoes in its manu- facture. The newer materials of this class, i.e., those formed of thin sheets impregnated by and cemented together with organic or synthetic resinous materials, depend very largely on the latter for their insulating value, but they are also affected to a considerable degree by the tempera- ture and pressure to which they are subjected during their manufacture. Class "I"- The high insulating value of molded mica depends almost entirely on the great dielectric strength of the mica, the other ingredients being employed merely to cement and hold the mica flakes together. MECHANICAL STRENGTH One quality of prime importance which a molded insulating piece must possess is mechanical strength. Years ago when porcelain, fibre, hard rubber and wood were the standard insulating materials, fibre was generally employed for those parts which were subjected to unusual stress. 100 MOLDED INSULATION As long as fibre, wood, or a good quality of hard rubber was used, metal parts were often embedded in, or fastened to the insulating parts by drilling and then threading and screwing, or by simply punching and riveting. The strength, toughness and resilient properties of those materials were such that these methods of manu- facture and assembling were not objectionable. Design- ing and manufacturing departments became accustomed to this treatment, and when the various new insulating materials were introduced they frequently entirely over- looked the fact that these newer substances might not possess the same mechanical characteristics as those with which they were familiar; and the old processes of drill- ing, riveting, etc. were attempted with unsatisfactory results. The usual consequence then was that these materials were condemned by the workmen because they were different from those to which they had become accustomed. This condition of affairs, more than anything else, retarded the introduction of molded insulating parts, and gave manufacturers of these parts untold trouble and expense, until it was demonstrated, that their pro- ducts possessed advantages sufficiently valuable to more than compensate for the apparent defect of requiring somewhat different treatment and handling. Fibre is still quite extensively employed in many shops, particularly for experimental work, and where on account of the small number of pieces required, the ex- pense of a die is a considerable factor in the cost per piece. However, even the newer fibre materials cannot compete with molded insulating parts if used in large quantities, and materials of this type are destined to con- stantly decrease in popularity, except for experimental PROPERTIES 101 and special work or where great flexibility, resiliency and mechanical strength are of first importance. The molded insulation products which have come nearest to fibre for strength and toughness are those of Class "E," the rubber compounds, and more lately those of Class "G," the synthetic resinous materials. Some- of the materials of both of these classes possess excellent mechanical strength and are equal, if not superior, in this respect to any. Porcelain is one of the very best insulating ma- terials we have, and wherever its brittleness is not a serious drawback, its use is recommended, particularly on account of its low cost. Contrary to general opinion, its tensile strength is high, but unfortunately its elas- ticity is very low and consequently it will not withstand shock, and should not be employed where it will be sub- jected to sudden strains or excessive vibration. Materials, which have successfully competed with and to a large measure have already replaced porcelain, are those of Classes "B" and "C," the organic and inorganic cold molded materials, and parts made of these materials when properly designed and used, give excellent results because they are less brittle and more resilient. Before the introduction of the cold molded ma- terials "B" and "C," the hot molded organic materials of class "A" seemed destined to surpass porcelain for a great variety of purposes, on account of their superior mechanical strength, but owing to their poor heat-resist- ing properties, they themselves have been in turn super- seded by the cold molded materials because of the better heat-resisting qualities of the latter, there being as a rule no characteristic difference in the mechanical strength of materials of Classes "A" and "B." The 102 MOLDED INSULATION inorganic materials of Class "C" possess a greater mechanical strength than the products of Classes "A" and "B," although they are not quite as strong as those of Classes "E" and "G." The materials of Class "F" are fairly strong, but they are seldom chosen for this reason. They are usually employed because of their ornamental appearance. No matter what insulating material is selected, manu- facturers should always bear in mind that it is advisable to design electrical apparatus so that the insulating parts may fulfil their primary function as an insulator, with- out being subjected to undue mechanical stress, and that this stress should be put upon parts and materials which by their very nature, are better able to sustain it. WEATHERPROOF QUALITIES The ability to resist the effects of moisture is a very essential requirement of a molded insulating material. No matter how good in all other respects a molded insulating material may be, if it is affected by moisture to such a degree that it either deforms, disintegrates or loses its dielectric properties to such an extent as to cause short circuit, it is useless. No insulating material is entirely unaffected by moisture or water. A material is said to be "non- hygroscopic" when it is affected by water only to so slight a degree that this defect can be safely disregarded. Moisture has no effect on materials of Class "D," although in their uriglazed condition they absorb water to a certain extent, but this is entirely overcome by the glazing process. Porcelain may, therefore, be considered as the best material in this regard. PROPERTIES 103 Class "C" (Inorganic cold molded materials). Moist- ure has no deteriorating effect on this class of products, but in their untreated condition, they absorb moisture to such an extent as to make them unsuited for pur- poses where they come in continuous contact with water. In their treated condition, however, the absorption of moisture is reduced to a point where it does not materially affect their insulating properties, and they have been used with success for the last 10 years for outdoor insulating purposes. Class "B" In the organic cold molded materials, the filler is so thoroughly saturated with the waterproof binder that the absorption of moisture is so slight as to be negligible, and these materials may properly be classified as waterproof. The writer knows of many instances where these products have been in continuous outdoor service for more than ten years without show- ing the slightest deterioration. Class "A" (The organic hot molded materials). When high class gums are employed in the manufacture of the binder, these materials are absolutely waterproof. Class "E"- The hard rubber compounds are thoroughly waterproof, although when made for high heat-resistance and containing an excess of asbestos fibre, they will absorb water to some degree. This, however, has no serious effect, except that it lowers somewhat the dielectric strength. . Class "G" The synthetic resinous products possess the same excellent waterproof qualities as the properly made materials of Class "A" at least, the five years during which these materials have been upon the market has so far justified such an opinion. 104 MOLDED INSULATION Class "F" The celluloid products are absolutely waterproof, while the casein compositions are not suited to use where they will be exposed to moisture. Class "H" Fibre has fallen into disrepute because of its very hygroscopic nature, but the newer class of this material is expected to gain favor because it does not exhibit this disadvantage. HEATPROOF QUALITIES During the last ten years operating conditions and the development in all electrical lines have made in- creased demands upon the heatproof qualities of electrical insulating parts, and the underwriters requirements in this particular, have become stricter and stricter, until today the heat-resisting properties of an electrical in- sulating part is one of the most important factors in the choice of such materials. The term fireproof is frequently used in describing molded electrical insulation, but in a strict scientific sense nothing is fireproof, and in a commercial or prac- tical sense, insulation is rarely required to be fireproof. The term heat-resistant or heatproof is employed to those materials which do not soften readily or at all under excessive heat; or which do not burn or char upon contact with flame or the electric arc, or will cease to burn as soon as the burning agent is withdrawn. The most heatproof materials obtainable today are Ihe Ceramics, the best known and most widely used product of this class being porcelain, and whenever con- ditions permit its use, it is to be recommended. It is, however, liable to crack under sudden temperature PROPERTIES 105 changes of wide range. Under such conditions, the lavite products are preferable, as they will withstand sudden and even violent variations of temperature some- what better. Where, for mechanical or other reasons, porcelain is not suitable, the choice lies between the organic cold molded materials, the inorganic cold molded materials or the synthetic resinous products. All these materials may be considered heatproof in that they will not soften or be otherwise disadvantageously affected when continu- ously subjected to a temperature of 100-deg. C., which is the usual maximum working temperature of electrical machinery. The hot molded organic materials (Class "A"), the rubber compounds (Class "E") and the organic plastics (Class "F") are all seriously affected by the continuous application of such a temperature. Of the three Classes "B," "C" and "G," the syn- thetic resinous materials (Class "G") are the strongest, and because of their excellent molding qualities and their neat appearance, they are to be preferred where cost is a secondary consideration. These materials will with- stand continuously a temperature of from 150-deg. C. to 250-deg. C., depending on the nature and percentage of the filling medium employed. For most purposes, however, such as in the construc- tion of lighting fixtures and electrical apparatus of all kinds where the .cost of the insulating parts is not of minor or negligible importance, and heatproof qualities are essential, the cold molded materials (Classes "B" and "C") are more suitable. It is not advisable to employ the organic cold molded materials (Class "B") for continuous temperatures above 300-deg. C., while the inorganic cold molded materials 106 MOLDED INSULATION (Class "C") are perfectly reliable under the continuous action of temperatures up to 900 deg. C. If, in the manufacture of materials of Classes "B" and "G," the ingredients are proportioned so that an inorganic filler is thoroughly and intimately inter- mingled with a proper minimum quantity of the organic binder, products can be obtained upon which the elec- tric arc has but little effect. In general, however, it is advisable to manufacture arc deflectors and all parts which are subjected to con- stant arcing and similar conditions, of the inorganic cold molded materials, as their inorganic nature precludes all possibility of softening or charring. While these materials are unaffected by arcing or momentary temperatures of 1500-deg. C., they should be used with caution for service where they will be sub- jected to continuous temperatures of over 900-deg. C., as may be the case in resistance insulators, for instance. Although materials of this type Class "C" are in use today for such purposes and are apparently giving satis- faction, nevertheless, it must be borne in mind that very high temperatures above 900-deg. C. sustained for too long a time are apt to split up the water of constitu- tion, and thereby affect the nature of these materials. But under these conditions, some of the constituents will fuse, and this fusion, if only partial, will offset the loss of mechanical strength, due to the dissociation of the water. However, it has been amply demonstrated that the inorganic cold molded materials are inert under con- tinuous temperatures of nearly 900-deg. C., sustained for long periods of time. The materials of Class "II," fibre, should not be employed where they will be subjected to the influences PROPERTIES 107 of the arc or continuous temperatures above 150-deg. C. The vulcanized products of this class are apt to warp at 100-deg. C. The organic hot molded materials (Class "A") will not withstand the electric arc, and they should not be exposed to continuous temperatures above SO-deg. C., owing to the low melting point of the binders employed. The heat-resisting properties of built-up mica (Class "I") are limited by the melting point of the shellac, and unless the sheets of mica are confined and positioned by some mechanical means, these products will not stand temperatures in excess of 100-deg. C. RESISTANCE TO CHEMICAL ACTION Materials intended to withstand the continued action of acids or alkalies must be carefully chosen. While most insulating compounds will resist these actions to a greater or lesser degree, few of them are proof against acids or alkalies for any great period of time. The only materials which can be safely employed for this purpose are those of Class "D," the Ceramics, and to a certain extent the products of Class "E," the especially compounded hard rubber materials. All other materials must be regarded with suspicion for such work. MACHINING OF MOLDED PIECES One of the chief advantages of molded insulation is that it can be delivered to the user in an absolutely finished state, and it is not intended to be worked by means of tools. However, with the exception of Class "D," all these materials can be worked with more or 108 MOLDED INSULATION less satisfaction, although it is not advisable to attempt it, but rather to design the parts so that no machining will be necessary. Class "H," however, may be worked with consider- able facility and this is the chief reason why these ma- terials continue to be used to a limited extent for almost every electrical application. COLOR AND APPEARANCE The color and appearance of molded insulating parts, while not usually of primary importance, are sometimes deciding factors. The color of the various insulating materials is gen- erally dependent upon the colors of their principal in- gredients, and only in special instances do coloring materials play an important part. Materials of Class "D," for instance, are usually white, but in some cases the glazing is done in various colors. In materials of Class "B" the color is usually black and depends upon the ingredient substances which cannot be changed. This material can be furnished with a very high finish. In materials of Class "C" the color is usually white or black, but these materials can be furnished in various colors. The materials of this class present a smooth, close-grained, attractive, appearance, but do not take a high polish. The materials of Class "A" are naturally black or brown, but by the introduction of coloring matter, they can be made in a wide range of colors. Materials of this class usually leave the die with a high polish. PROPERTIES 109 The natural color of materials of Class "G" is a reddish brown, but they are very often made in black and can be produced in various colors by the addition of coloring matter. Their appearance is the same as is Class "A." Class "E" The asbestos-rubber compounds are usually furnished in their natural gray-brown and the hard rubber in black color, but they can be made in a variety of colors. Most of the hard rubber compounds take a very high polish. The materials of Class "F" are particularly adapted to coloring and can be furnished in a very wide range of colors and finishes, and for this reason are occassionally used on account of their appearance. Materials of Class "H" are furnished in a variety of colors, but are usually gray, black or red. AVhere an ornamental appearance is essential and a high polish is required, designers should remember that the quality of the surface of the products of Classes "A," "E," "F" and "G" is due to the method of manu- facture and the character of the material, and that they leave the die with a high polish, or that same can be obtained by a simple buffing process. On the other hand, the products of Classes "B" and "C" while they come from the molds with a smooth and continuous surface, present a flat and lusterless ap- pearance, and in order to give them a high polish they must be ground on fine .abrasive wheels or carborundum or like material, and then buffed. It is self-evident that such treatment cannot be satisfactorily applied to parts having small or intricate projections and depressions, or to parts of irregular and complicated shape. 110 MOLDED INSULATION MOLDS AND DIES In the molded insulating trade these terms are synonymous. Most electrical engineers are familiar with some methods employed in the construction and operation of the molds in general use in the manufacture of insulating parts. The molds play a very vital part in such manu- facture and are often the cause of serious difficulty to the manufacturer, and consequent misunderstanding be- tween him and his customer. The author will as briefly and comprehensively as possible sketch the more impor- tant factors in their construction and use, to enable the user, through a better understanding of their operation, to avoid those elements of design which tend to compli- cate manufacturing operations. This knowledge will facilitate the selection of forms for his insulating parts which, while rendering them no less effective for his pur- poses, will enable the manufacturer to produce pieces of minimum cost, maximum efficiency and neat appearance. Frequently designers, when bringing out new forms, insist on having dies of the cheapest construction made in order to get out a few sample pieces. This results in serious trouble for the manufacturer, and dissatisfaction for the customer until a proper mold is substituted. This is especially true when the form of the piece is in any way complicated by holes, projections, or irregu- lar surfaces, and unless the molds are made of the very MOLDS AND DIES 111 best steel, and all the parts come, together with a per- fect fit, the molded pieces will be more or less misshapen and have burrs or fins on their edges. These imperfec- tions are a frequent cause of complaint. It is, therefore, very important to have the molds of such quality that they will wear for as long a time as possible without producing pieces with these defects. All dies will eventu- ally wear out, and the only remedy then is to replace the worn parts or make complete new dies. The form of the piece and the character of the material to be molded play an important part in this particular, and a mold may show more wear after a run of 10,000 pieces of one material than it would after turning out 100,000 pieces of another material. TYPES OF MOLDS OR DIES USED IN THE MANU- FACTURE OF MOLDED INSULATION There are two different classes of dies in general use. They are known as " OPEN DIES" and "CLOSED DIES." The term "OPEN" is applied to that class of dies or molds which are composed essentially of two flat pieces in one or both of which a recess is provided to hold the material to be molded. In operation, these plates come together at a cutting edge which chops off the excess of material which has been squeezed out of the recess containing the molded part. The term "CLOSED" is applied to that class of dies or molds which are composed essentially of a plunger and a box. In operation, just enough material to form the part is placed in the box; the plunger then enters the box and forces the material to all parts of the mold. 112 MOLDED INSULATION In practice these dies are made with two plungers; the upper plunger, which, generally speaking, does the com- pressing; and the lower plunger, which forms the bottom of the mold, and which, after the piece is formed, raises to push the piece from the mold. Both "OPEN" and "CLOSED" dies are in general use for the manufacture of hot molded materials, while only closed dies are employed in the manufacture of cold molded products. FIG. 1 Figure I represents an open die, such as is used in the manufacture of materials of Classes "A," "E," "F" and "G," when such materials are prepared in sheet or cake form and placed between the compressing plates in a warm or plastic condition. This die, which is intended to produce a disc or short cylinder having parallel sides, is made in three parts, the Bottom Plate "A," to which is screwed or otherwise fastened the middle plate "D," containing MOLDS AND DIES 113 the opening "C," in which the piece is to be formed, and the top Plate "B," which closes the die, guided by the pins "E." In operation the die is heated; an excess of material is placed in the cavity "C;" the die is closed; the Cutting Edge "F" cuts off the surplus material, which has been squeezed into the depression "G" formed to receive it. The die is then cooled and opened; the plate "D" is released from the plate "A, 1 ' and the finished piece is pushed out by the fingers or other means. FIG. 2 If the sides of the piece instead of being straight are tapered, a simpler form of mold shown in Figure 2 can be used. In this case, the die can be made in two parts, and after the piece is formed and the die cooled, the piece, due to its tapered form and the shrinkage incidental to cooling, can be readily removed by simply inverting the die and rapping it till the piece falls out. 114 MOLDED INSULATION FIG. 3 In Figure 3 is shown a closed die, such as is used in the molding of materials in a heated state and comprises a Box "D," an Upper Piston "C," and a Lower Piston "B," having between them a cavity "A" in which the piece is formed. It will be noticed that the upper piston is longer than the lower one. In operation the Box "D," with the Lower Piston "B" is placed upon a heated press table and the material to be pressed is placed in the Cavity "A," see Figure 4. Before pressing, this material occupies a volume con- siderably greater than the volume of the finished piece, and for this reason the Top Piston must be longer than the Bottom Piston, since it must travel into MOLDS AND DIES 115 FIG. 4 the box a sufficient distance to compress the material to be molded to the required density. The Top Piston is now placed in the Box and the Upper Platen of the press, which is also heated, is brought down by hydraulic or other pressure on the Piston "C" until its top surface is 'flush with the top of the Box "D." The die is now held between the heated plates of the press until the material in the Cavity "A" is melted. The steam is then shut off and cold water is run through the plates of the press until the material in Cavity "A" is sufficiently cooled to render it hard enough to permit of its removal from the mold. 116 MOLDED INSULATION Sometimes the walls of the Box "D" are provided with channels through which the steam and water are run to expedite the molding process. In practice, steam is kept on the press plates and molds just a sufficient length of time to properly melt the material to be molded, and the water is run through only long enough to permit of the ready removal of the finished piece, as the time consumed in these opera- tions determines the output of the press, and so directly affects the cost of the piece. In making parts, such as bushings and other pieces having holes in them, which are formed by pins incorporated in the mold, the piece must be removed from the die before the shrinkage has progressed to a point where the material would seize upon the pins and thus prevent its easy removal from the mold. It is necessary that the Pistons "B" and "C" should be a nice fit in the Box "D" in order that the pieces may come from the dies without burrs, which would otherwise form at "E," Figure 3. This is particularly true in the case of materials of Classes "A," "E," "F" and "G ? " which come from the molds in a finished and highly polished condition, and are not subjected to any further finishing treatment. It is obvious, however, that constant use will eventu- ally cause the box and plunger to wear, when the mold will necessarily produce defective pieces. This type of die may be used for molding any class of material, but is usually employed in the hot molding of such materials as those of Classes "A," "E," "F" and "G." Figure 5 shows a die of the type used in the manu- facture of cold molded materials, such as those of Classes "B," "C" and "D." This die embodies the same gen- MOLDS AND DIES 117 FIG, 5 eral principles as those shown in Figure 3, but in this case, the Upper Piston "C" is attached to the Plate "H," which in turn is attached to the upper platen of the press. The Box "D" is attached to a Plate "K," which is fastened to the bed of the press and the lower piston is operated by means of the Throw-out Rod "L" connected to the lower plunger of the press. The operation is as follows: The mold is filled with the material to be pressed as in the case of Figure 3, and the piece is compressed 118 MOLDED INSULATION in a similar manner. At this point the similarity ceases. After the piece is pressed, the Upper Piston "C" is with- drawn from the mold and the Lower Piston "B" is raised by the Throw-out Rod "L," and by this means the piece is expelled from the mold. The Piston "B" now descends to its normal position at the bottom of the mold and it is then ready for re-filling without having to undergo any heating or cooling operations. When dies of this type are employed, the materials are either weighed or measured beforehand, and just suffi- cient is introduced into the die to form the piece. B FIG. 6 Figure 6 shows a molded piece with a metallic insert "A" molded in. Such pieces can be easily produced in MOLDS AND DIES 119 materials of Classess "A," "B," "C," "E," "F" and "G." However, if absolute accuracy, together with a highly polished piece is required only Classes "A," "E," "F" and "G" can be considered. Class "B" could be advantageously molded into this shape, but a slight varia- tion must be tolerated and only the exterior surface can be polished. Class "C" could be molded accurately, but it would be necessary to increase the radius at "B" as much as possible. FIG. 7 Figure 7 shows the design of the mold from which this piece is produced, and is here represented to illus- trate the manner in which inserts are molded into the materials. These inserts should be provided either with 120 MOLDED INSULATION a knurled or some other rough and irregular surface so that they may be firmly gripped by the material. Another point of interest is the production of letters or figures on molded pieces. On materials such as those of Classes "A," "E," "F" and "G," where the pieces come from the molds in a polished condition, no difficulty is experienced in produc- ing raised letters. However, if such materials as those of Classes "B" and "C" are used, where the pressed pieces do not come from the molds in a finished condition, but must be hardened, ground, and polished, raised lettering cannot be used, as the grinding and polishing of the surface would destroy them. Therefore, it is essential in all cases where pieces are to be made of materials in Classes "B" and "C," that the designer employ some other means to incorporate the lettering on his pieces. An excellent method and one which has become a standard for use in connection with these materials is to recess a portion of the surface, leaving the letters raised and flush with the main surface, so that the tops of letters receive the same polish as the rest of the surface. Metal inserts are never molded in pieces made of the ceramic materials. Openings or recesses are molded, into which the metal parts are inserted and held in place by riveting or other mechanical means. Usually sealing wax or some other form of cement is used to fill the recesses, covering the screw heads or nuts to pre- vent the exposure of live parts. Figure 8 shows a typical cross section of a molded insulating box or cover, and illustrates very nicely some of those elements of design constituting a part of that unwelcome legacy which comes to the molded insulation manufacturer from his predecessors who worked with MOLDS AND DIES 121 . A R^S^WsN^^ ^ \ B FIG. 8 FIG. 9 materials of a very different nature. This cross section shows a cover or box having thin walls and sharp interior corners. In other words, a typical metal box or cover, which offers no difficulty whatever to the metal stamper, but which is not well adapted to meet the requirements of the modern molded insulating materials; it is a good, if very simple, ex- ample of the trouble designers often make for them- selves and the molded insulation manufacturer by failing to bear in mind that the characteristics of modern ma- terials differ from those formerly in common use. If, as often happens, the apparatus, of which this cover is to form a part has been made, or the component metal parts which compose it are already under construction or ordered from some other sources before the molded insulation manufacturer is consulted, the designer of such a cover may find himself in trouble and be fortunate 122 MOLDED INSULATION if he has put himself to no greater inconvenience than to greatly restrict the number of materials from which this part can be made. The design of this cover, Figure 8, is entirely un- suited for manufacture from materials of Classes "B," "C" and "D," which are among the best materials from which to make such parts as switch and fuse box covers, owing to their high heat-resisting qualities, but the straight thin sides of the box practically make it impossible to form this piece of these materials, and it would be very difficult to properly mold the thin parallel sides, as the material would not be compactly pressed at the top of the sides, Point "A," unless a complicated mold were employed, which would exert the necessary extra pressure. FIG. 10 FIG. 11 Should there be room inside the box to thicken the side walls particularly at their base point "B" MOLDS AND DIES 123 Figure 9, and so give the sides a taper or draw, the design would be improved. Even this added thickness is not sufficient in most cases, as it would be of great advantage to put as large a radius as possible in the corners "C," as is shown in Figure 10. Figure 11 shows a cover having the proper thickness of walls, with the necessary draw or taper to the inside, and a generous fillet or curve in the corners to make it an ideal design for the proper flowing and molding of the materials of Classes "B," "C" and "D." This form is equally well suited to materials of Classes "A," "E," "F" and "G," although the free flowing qualities of these materials do not make it imperative that the piece be designed in this manner. Figure 12 shows a receptacle box of rather intricate form. Formerly such pieces were made exclusively in porcelain, but are now also extensively manufactured in the cold molded materials of Classes "B" and "C." The synthetic resinous materials of Class "G" are splendidly adapted to producing pieces of this character, but they are very rarely used because of their high cost in comparison with Classes "B," "C" and "D." In a previous illustration, particular stress has been laid on the desirability of designing such pieces with thick walls and ample radius at the bottom, particularly when made of materials in Classes "B" and "C." Too much emphasis cannot be laid on these points. Figure 12 shows that it is possible to produce pieces of this design in these materials, but it is not accom- plished without some difficulty, and in some cases it requires a very complicated mold. It also becomes nec- essary to sacrifice the mechanical strength in order to have a mixture of material which has the viscosity necessary to meet the molding requirements. 124 MOLDED INSULATION x- SECTION x-r FIG. 12 A much more satisfactory design for both the cus- tomer and manufacturer would have resulted if walls "A," "B," "C" and "D" were made somewhat thicker; MOLDS AND DIES 125 also by the addition of a radius at Points "E," "F" and "G." In molding pieces of this character in porcelain, it has been the custom to allow for a variation in the dis- tance "H" by making the holes about 1/32" larger than the diameter of the screws which fit in these holes. Although the manufacturers of materials of Class "B" generally claim that they can mold such pieces more accurately than those made in porcelain, it would be advisable for the designer not to figure on absolute accuracy in a piece of this nature, if he intends to have them made of this material. He should allow for a few thousandths of an inch variation. Designers frequently assert that they are limited as to space, both inside and outside, of such parts, but, with a better understanding of the fundamental require- ments of the molding art, and a fuller realization of the difficulties they make for the insulation manufacturer, and the consequent higher cost and poorer quality of the pieces they obtain, they can originate pieces better adapted to molding in the materials they require. By giving a little more consideration to the molded insulating parts before the design of the apparatus, in which those parts are to be incorporated, has become ir- revocably fixed, designers would materially help them- selves as well as the insulating manufacturer. Figures 13 and 14 show two insulated knurls of different design, serving the same purpose, and the molds for producing them. Figure 13 shows the original or incorrect design and Figure 14 the same piece altered to facilitate the molding, increase the production, improve the appear- ance of the piece, and to make the mold much easier and N less complicated to manufacture and handle. 126 MOLDED INSULATION FIG, 13 The piece shown in Figure 13 presents numerous difficulties. The groove "A" on the side and also- this type of knurling makes it absolutely necessary for the piece to be surrounded by a number of loose parts which must be removed from the Box "C" in order MOLDS AND DIES 127 to free the piece from the same. This can readily be seen from the section shown. At the junction of these loose parts, a finn or burr will be formed which must be removed, thus increasing the cost of manufacture and affecting the appearance of the piece. Another bad feature of this design is the thread molded in the material above the metal insert "B." As all molded insulating materials shrink more or less, the threads in the molded material will be smaller than those in the insert. On the other- hand, the design as shown in Figure 14 is much simpler and less complicated. The groove on the side is entirely eliminated and the style of knurling is changed from braided to straight, thus making it pos- sible to push the piece from the mold by merely press- ing it from the bottom towards the top. This, of course, does away with the loose parts and eliminates all burrs and produces a perfectly clean, smooth, and neat appear- ing piece. It will also be noticed in this figure that the insert "B" has been lengthened to accommodate the full depth of thread which would otherwise be partly molded in the material. The sloping sides or pointed appearance on the end is to allow the material to flow off and around it instead of packing tightly and crushing on the top as it would do if it were flat. Therefore, the design as shown in Figure 14 is strongly recommended whenever it is possible for two important reasons : First: The lower cost of production. Second : The freedom from burrs which will form at the junction of the split portions of the mold made necessary by the groove on the side, and the use of this type of knurling. 128 MOLDED INSULATION These conditions apply not only to insulated knurls, but to any pieces of similar design or construction. c D b (o) o (sy @ FIG. 15 Figure 15 represents a molded base with a projec- tion "A" and numerous counterbored holes. A piece of this design is readily molded of the hot molded ma- terials "A," "E," "F" and "G," also of the ceramic materials, Class "D." It can also be molded of ma- terials of Classes "B" and "C," if certain changes in design are made. In the first place the flowing qualities of these ma- terials, Classes "B" and "C," make it difficult to mold such shapes as projection "A," unless molds of com- MOLDS AND DIES 129 plicated construction are resorted to. Such pieces can be made perfectly practical for cold molding by the introduction of two simple modifications. First by the addition of a radius around the base, as is shown at " B " in Figure 16, and secondly by giving a slight draw or taper to the sides, which is also shown in this same figure. Co." C." 0) P) loj O i' 5 ' ] \J (0) I I I I FIG. 16 With these modifications, such a projection can be readily molded true in form, neat in appearance, and with the proper mechanical strength. It is possible to mold pieces with this projection exactly as is shown in Figure 15, but the modifications suggested are simply to increase production and to reduce the cost. 130 MOLDED INSULATION Another point is the shape of the counterbores. In Figure 15, two counterbores are shown which are so close together as to leave a very thin separating wall, as at point "C." At point "D" there is also a very thin wall produced between a single counterbore and the side of the piece. When wood and fibre were extensively used and insulating pieces were machined from blocks and sheets, this was a logical design, but it is not now well suited to the peculiarities of modern insulating mediums. In order to adapt this piece to the present require- ments of cold molded materials, it would be advisable to eliminate these thin walls by cutting them away, as is shown in Figure 16, thus making one elongated counterbore, and opening the other to the outside of the piece. If, how r ever, it be necessary to have a barrier of this kind separating these counterbores owing to elec- trical requirements, the designer should place these holes far enough apart and away from the edge of the insulat- ing piece so as to allow a wall of ample thickness. In all cases, the depth of the counterbores should be no greater than the requirements of the piece, and ample draw or taper should be allowed on the sides of the same in order to allow the easy removal of the piece from the surface of the pistons in the mold. All holes should be made as large as convenient for their purpose, so that the pins in the mold which form them may be as rugged as possible. Figure 17 is a typical piece of molded insulation used as a strain insulator in overhead line construction and shows how the insulating material is molded around the metal parts. The hot molded materials of Classes "A," "E" MOLDS AND DIES 131 FIG. 17 and "G" are well suited to the manufacture of such parts, and while formerly the rubber compounds of Class "E" were extensively used, to-day the materials of Class "A" practically monopolize this field, chiefly on account of their lower cost. For this latter reason the synthetic resinous products of Class "G M have not come in use for such purposes, 132 .. MOLDED INSULATION their cost being- too high, although the properties of this material seem to indicate that it would stand up well as an insulator under the severe climatic conditions to which such insulators are exposed. The cold molded materials of Classes "B" and "C" are used for the manufacture of such pieces, but to a limited extent. As they do not possess the necessary, plasticity to be molded as easily as the hot molded pro- ducts, the molding of such parts causes difficulties owing to the high pressure required to obtain perfect molded pieces. The hot molded materials of Classes "A," "E" and "G" are readily molded with comparatively little pressure while in a hot plastic condition around the two metal parts which are held in position at the outer ends by the die. In ease of molding materials of less plastic nature, such as Classes "B" and "C." around these two metal parts, such materials do not flow easily around the metal inserts, but have to be forced around them by means of high pressure. These inserts, held in position only by the die at their extremities "A" and "B," and having no central support, are apt to be distorted, rendering the finished piece imperfect and useless for service. The Figure 18 illustrates a magneto insulator as is commonly used for automobile work. Formerly such parts were made either of materials of the rubber compounds of Class "E" or else of special .grade ma- terials of the organic hot molded products of Class "A." As the magnetos are usually placed near the hot engines, and the insulating parts come in contact with hot oils and gasoline vapors, considerable trouble was previously experienced with the materials above men- MOLDS AND DIES 133 FIG. 18 tioned for parts of this nature. This trouble was caused by either the materials not being heatproof enough or else by being affected by the oil and gasoline vapors. 134 MOLDED INSULATION The ceramic materials of Class "D" could not be used, as the molding could not have been done accurately enough or no metal parts could have been molded in, and also these materials could not stand the vibration to which they would necessarily be subjected in an auto- mobile. The inorganic cold molded materials of Class "C" could not have been satisfactorily employed for the molding of these parts for two reasons. They could not be molded accurately enough, and furthermore, as such parts should be safe to withstand at least 3,000 volts continuously, the insulating properties of this product would not be sufficient. The materials of Class "B" could not be molded accurately enough, and they are primarily adaptable for use under working conditions below 1,000 volts. The products best suited for such parts and which fulfill all the requirements are the materials of Class "G." These materials are already almost entirely em- ployed for such purposes. In the molding of such shapes of materials of Classes "B" and "C," the four inserts A, B, C and D would present some difficulties owing to the high pressure re- quired in the pressing. These inserts, as shown in Figure 18, can only be supported at their extremities, and there would be great danger of their distorting between the supporting points. Therefore, the principal feature to bear in mind is the position and shape of the inserts, and that they be designed and located so that they may be easily and firmly held in 'position and sufficiently supported so that they will not bend or distort during the molding process. SELECTION OF MATERIALS 135 SELECTION OF MATERIALS IN RELATION TO DESIGN AND USES OF INSULATING PARTS The molding, physical, mechanical, electrical, and other properties of the different classes of materials. as they affect their relative adaptability to the produc- tion of various molded articles, has been treated in previous chapters. This question is, however, of such vital importance to the designer and electrical engineer that the author has thought it advisable to offer some further suggestions, aided by illustrations, which, it is hoped, will prove helpful to those having to select the material best suited to their purpose from among the classes treated in this work. Since entirely legitimate differences of opinion must exist as to what may be re- quired of an insulating material for a given purpose, these suggestions are evidently not offered as final or as applying to every circumstance that may arise. The author's long and intimate experience in manu- facturing materials of all of the classes treated, as well as his personal and business relations with the foremost electrical designers and engineers, permitting him, as they do, to base these suggestions on the experience of the past ten years both in the laboratory and in actual service, leads him to believe that they will be of some assistance to those seeking information. No reference to Class "H," the fibre products, will be made, for, as previously stated, materials of this class are principally 136 MOLDED INSULATION used in the form of sheets, rods, and tubes only, and machined into the desired shapes. Class "I," mica molded articles is also excluded, they being restricted to the usual known micanite segments, rings, tubes, sheets and such forms. When referring, therefore, to parts which may be molded of materials of all classes, it must be understood that Classes "H" and "I" are not included. PLATE PLATE II ILLUSTRATIONS 139 Plates Nos. I. and II. Parts of familiar design are here shown, which may be molded from materials of all of the six classes, though for prac- tical reasons, the ceramic products of Class "D" are almost ex- clusively used at the present time in the production of these and similar parts. This is partly due to the excellent dielectric and physical characteristics of porcelain, but principally to its low cost. As a result, the combined production of such parts from materials of the other classes is far below that of Class "D," the ceramic products. Ten years ago, porcelain alone was available for such parts, but since that time other 'classes of molded materials, such as those of Classes "B" and "C" have grown in favor, so that at the present time the designer of electrical appliances is no longer limited to porcelain, but has at his disposal both the inorganic and organic cold molded materials of Classes ""B" and "C," giving him a wider range as to appearance and physical qualities, where very low cost is not an absolute essential. The hot molded materials of Class "A" are also available, and sometimes used where resistance to heat is not required. Also the synthetic resinous materials of Class "G," but only when cost need not be considered. PLATE III ILLUSTRATIONS 141 Plate No. III. VARIOUS TYPES OP SWITCH HANDLES Appearance and finish are the essentials in such parts. They are also generally molded with metal studs or blades in place. The production of such .parts is practically limited to the hot molded materials of Class "A," which, high heat-resistance not being of importance, best fill the requirements as to finished appearance and low cost. The synthetic resinous materials of Class "G-"' are also entirely suitable, but are debarred owing to their high cost. The cold molded materials of Classes "B" and "C" may be molded into such shapes, but owing to the uneven surfaces, they cannot be polished and finished as well as materials of Class "A." The ceramic products of Class ' * I) ' ' were at one time em- ployed to a limited extent, but have now been almost entirely superseded. Materials of Class <'E" (rubber compounds) are no longer used for such purposes. PLATE IV ILLUSTRATIONS 143 Plate No. IV. A FURTHER VARIETY OF SMALL SWITCH HANDLES AND KNOBS OFFERING MORE LATITUDE IN THE CHOICE OF MATERIALS THAN THOSE SHOWN IN PLATE NO. Ill The first points for consideration in selecting a material for these parts being cost and appearance, the products of Class "A" are most adaptable, though these forms, being more regular than those shown in Plate No. Ill, and being readily and rapidly polished, may also be produced of the products of Class "B," with very little increase in the cost. In cases where heat-resistance is required, the materials of Class "B" are, there- fore, used, being very little inferior to those of Class "A" in appearance, and possessing all of the other desirable properties. The ceramic products, Class "D" are not used for such parts, and materials of Class "G, " synthetic resinous products, while entirely suitable, can only be used when cost need not be considered. The inorganic materials of Class "C" are not used, owing to their inferior finish, while the rubber compounds of Class "E, " at one time employed, are now rarely, if ever, seen. PLATE V ILLUSTRATIONS 145 Plate No. V. MOLDED ARTICLES MOSTLY FOUND IN TELEPHONE WORK Eesistance to heat being unimportant, materials of Classes "A" and "E" are most suitable, particularly for parts illus- trated by Figures A and B, owing to the high and permanent finish required, and by Figure C, owing to the multiplicity of small and delicate metal parts which are molded into the material. While materials of Class lt G ; ' are in every way suitable, their comparatively high cost has, up to now, precluded their general use. The materials of Classes "B" and "C" are entirely unsuit- able for the style of pieces shown by Figures A and B, though in some cases they might prove satisfactory for pieces similar to Figure C. Materials of Classes "B" and "C" are suitable for molding parts shown in Figures D, E and F, particularly the latter in the larger sizes, or where used in installations in which they may be exposed to heat. PLATE VI ILLUSTRATIONS 147 Plate No. VI. OVERHEAD LINE INSULATORS Formerly, these parts were made of the rubber compounds of Class "E," but today they are almost exclusively made of the organic hot molded materials of Class "A." Materials of Classes "B" and "C, " while desirable owing to their heat-resisting qualities in case of line short circuits, have not been successfully used, due to difficulties in molding the forms and metal inserts required, as has been more fully ex- plained in considering similar parts in a previous chapter. Materials of Class "G" would be ideal for this purpose were it not for their high cost. Whether or not this may be justified by their superior properties has not yet been definitely determined, as the synthetic resinous products are of too recent origin and sufficient comparative data as to behavior under service conditions is not available. PLATE VII ILLUSTRATIONS 149 Plate No. VII. MAGNETO DISTRIBUTOR, COLLECTOR, AND SIMILAR PARTS Hot molded materials are only suitable for molding such parts, as has been more fully explained in considering a similar piece in the chapter on molds and dies. In the past, materials of Classes "A" and "E" were used, but recently they have been superseded by the synthetic resinous materials of Class "G' ; which are pre-eminently adopted for this purpose to the exclusion of materials of any of the other classes. Owing to their heat-resisting qualities and lower cost, repeated efforts have been made to render the materials of Classes "B" and "C" adaptable to this purpose, but as yet without any marked success. ID x -* :: * Jf ~~~ t j~ ~~"_.r~^ Iz -^ PLATE VIII ILLUSTRATIONS 151 Plate No. VIII. A FURTHER SERIES OF PARTS SIMILAR TO THOSE OF PLATE NO. VII These parts are best made of the hot molded materials of Classes "A" and "G." Formerly, only the materials of Class "A" were available, but to-day the synthetic resinous materials of Class "G" receive favorable consideration where cost is of secondary importance. Cold molded materials of Classes "B" and "C" are not recommended, and the ceramics of Class "D 77 are entirely unsuit- able. Pieces of this style, shown by Figures A and B particularly, can only be successfully produced in materials of Classes "A" and "G." In Figure A, this is due to the insulated wires which could not be properly molded into place under the cold molding pro- cesses, and would further be rendered useless through the destruc- tion of their insulating cover by the high temperatures to which these products are usually subjected after the pressing operation. In Figure B, this is due to the metal parts which could not be successfully molded in under the cold molding processes. In fact, the accuracy of dimensions and complication of shapes required in parts shown in this cut can only be produced with facility, in the materials of Classes "A" and "G," and therefore, materials of Classes "B" or "C 77 should only be con- sidered in special cases where the peculiar characteristics of these materials may be necessary. \ \ PLATE IX ILLUSTRATIONS 153 Plate No. IX. A SERIES OF INSULATING HANDLES In the United States, these parts have up to the present time been almost entirely made of wood, though to a lesser -extent, materials of Class "A' have been used, and very re- cently materials of Classes "B" and "C" have been con- sidered. , It would seem strange that, while in Europe, more especially in Germany, the strict regulations of Fire Underwriters have -debarred wood as unsafe, no strong movement has taken place in the United States in favor of molded materials, though this is probably due to the cheapness of wood. It is, however, the author's belief that, as fibre and wood have been superseded by molded materials for other purposes, they will, in the near future, be displaced by molded materials. The higher cost will be more than compensated by superior -dielectrical and physical qualities. Such switch handles are used under varying conditions of heat and moisture, rendering them liable, when made of wood, to shrink or expand, with the result that metal parts will split the handles or become loose, and in consequence be a source of actual danger. Owing to the great number of suitable molded materials available, no difficulty should be experienced in selecting a satisfactory product. For this purpose the synthetic resinous materials of Class "G" are the best where cost need not be con- sidered, but are closely followed by the hot molded materials of Class f< A" and, more recently, by the cold molded materials of Class "B." D I Of PLATE X ILLUSTRATIONS 155 Plate No. X. A SERIES OF CHARGING OR CONTACT PLUGS AND SIMILAR PARTS These pieces being subjected to very rough treatment in service, require a material which is tough and will not chip or crack under hard blows. Owing to the high amperages generally carried by these parts, heat-resistance is an essential to prevent any danger of fire or deterioration of the insulation by charring, when contacts are made and broken. Until recently materials of Class "A" were used, but they have now been discarded as unsafe owing to their lack of resistance to heat. Vulcanized fibre is at present very much in favor owing to its toughness and non-inflammability, but still leaves much to be desired as it will in time char, and is very sensitive to conditions of moisture and dryness in -the atmosphere which cause it to distort with a consequent displace- ment of metal contact parts. In view of the .above, and the further fact that fibre must be machined to obtain the desired shapes, it would seem that the molded products will in the very near future be called on to advantage and fibre entirely superseded. Materials of Classes "B," "G" and "G" will be found well adapted to this purpose, owing to their high heat-resistance and indifference to moisture, "B" and "G" being used where cost is a consideration, and "G" for parts of intricate shapes where cost may be disregarded. The ceramics, Class "D," are entirely unsuitable, and the rubber compounds of Class "E" are seldom used. The parts shown in the plate with the exception of Figure A, made of synthetic resinous material, Class "G," and Figure B, made of hot molded organic material of Class "A," are all made of the cold molded materials of Classes "B" and "G" and have been in successful commercial use for a number of years. : * ! Aft PLATE XI ILLUSTRATIONS 157 Plate No. XI. VARIOUS CONNECTOR OR PLUG PARTS PRINCIPALLY USED WITH ELECTRIC FLAT IRONS AND OTHER ELECTRICAL HEATING APPLIANCES The primary requisite for such parts is resistance to heat, as they must necessarily come in direct contact with the hot metal parts of the appliances which they connect to the source of current. Under normal conditions, 300 C. without softening or other deterioration is the usual temperature limitation. Furthermore, these parts being furnished as part of a household article, must be well finished in appearance. Before the introduction of the cold molded organic ma- terials of Class "B," the only available products were porcelain, and some molded material depending on a large proportion of asbestos for the necessary heat-resistance. The former, owing to its brittleness and consequent liability to chipping has been almost totally abandoned, except in a few cases, where it is protected by an outer metal casing. The latter, owing to its heavy asbestos content, was rough and un- sightly, and, therefore, discarded. At the present time, materials of Class "B" above referred to, are almost exclusively used, though in some exceptional cases of special design, materials of Class "G" are preferred, owing to their higher heat-resistance. Materials of Classes ' ' E ; ' and "G" are not used, partly owing to their prohibitive cost, but principally because they are not as heat-resisting as Classes "B" and "G." PLATE XII ILLUSTRATIONS 159 Plate No. XII. TERMINAL BUSHINGS, CONTACT PARTS, ETC., REQUIR- ING HIGH HEAT-RESISTING QUALITIES The majority of these pieces are used to insulate contacts of electric flat irons or other heating appliances, and, being permanently located inside of the latter or even attached directly to the heating element, must necessarily stand continuous high temperatures, the minimum requirement being 800 C. While the ceramic materials of Class "~D' would stand the heat required, .they have been little used for this purpose, due to the impossibility of molding metal contacts in place, and the attainment of the required degree of accuracy to insure a proper fit between the male and female contacts. Materials of Class "A" are, of course, entirely unsuitable, while those of Classes "E" and "G," and even Class "B," are not sufficiently heat-resisting. The only remaining available materials are those of Class *'G" which, when made with a proper regard for the heat conditions to be met, are entirely suitable and almost exclusively adopted for this purpose. PLATE XIII ILLUSTRATIONS 161 Plate No. XIII. ARC DEFLECTORS, SEPARATORS AND SIMILAR PIECES USED IN ELECTRIC CONTROLLERS AND AUTOMATIC APPARATUS SUBJECTED TO CONTINUOUS ARCING By referring to the previous treatment of this subject, it will be readily understood that no material containing organic substances in any form could be considered for this purpose. The only suitable materials, therefore, are the ceramics of Class "D," and the cold molded inorganic products of class "C."' The latter predominate, however, owing to their mechanical ad- vantages, porcelain being used only in a few instances. PLATE XIV ILLUSTRATIONS 163 Plate No. XIV. RAILROAD THIRD RAIL AND SIGNAL PARTS Figures A, B, C and D illustrate a series of third rail insulators for service on the regular 660 volt circuit. Figures C and D are satisfactorily produced in the materials of Classes "A," "B, "C," "D" and "G," though the ceramics predominate at the present time owing to their low cost. Figures A and D can only be produced in the materials of Classes "A," "B," "C" and "G," owing to the heavy metal parts which are molded in place. As regards suitability, it is generally accepted that the ceramics are superior regarding their dielectric and physical attributes, while the products of Classes "A," "B," "C" and "G" are superior mechanically. The essentials are dielectric and mechanical stability under long term of service in all weather conditions; these have been- successfully met by materials of Classes "B," "C" and "G" under observation for four years in actual use.. The ceramics, though satisfactory in every other respect and lower in cost, are liable to excessive breakage. The other parts shown in this cut, used in electric signaling apparatus, are now made in materials of Classes "G" or "C. M The former are preferred when absolute accuracy is re- quired, but where variations of from 5 to 10 thousandths per inch may be allowed, the materials of Classes "B" and "C" are -very suitable. Materials of Classes "A" and "E' ; are rarely used for such purposes. I PLATE XV ILLUSTRATIONS 165 Plate No. XV. MOLDED BASES AND COVERS Hitherto, such parts have been cut from slate and fibre, but more recently there has been a very distinct tendency in favor of molded materials with the preference given, to pro- ducts of Classes "C" or "G," and to a lesser degree, Classes 11 A" and "B." Accurate molding and low cost, as well as dielectric and mechanical suitability have placed materials of Class "C" in the lead, while Class "G" has served for special purposes. . The ceramics of Class "D M are not as suitable, owing to the difficulty of obtaining perfectly flat surfaces. o O j, O I^BW^^H^^^^^K PLATE XVI ILLUSTRATIONS 167 Plate No. XVI. SPECIAL MOLDED PARTS USED IN CONNECTION WITH ELECTRIC MOTORS, FANS AND APPLIANCES Materials of Classes "B," "C" and "G" are the most suitable for such parts, as the apparatus in which they are used, is, at times, liable to overheating and it is, therefore, impor- tant that the insulation used should stand temperatures of not less than 100 C., without softening. Materials of Class "D" are used, owing to their low cost, but are gradually being superseded, owing to the greater accuracy and better mechanical features obtained with materials of the other classes. Materials of Class "G" can be molded in such shapes with absolute accuracy, while materials of Classes "B" and "C" require a variation allowance of a few thousandths per inch. PLATE XVII ILLUSTRATIONS 169 Plate No. XVII. SWITCH BASES, COVERS AND RECEPTACLES Ten years ago porcelain was the only material used for these bases and receptacles, while the covers were made of Class "A," or more often of stamped metal lined with insulating paper or fibre. Since that time, however, the introduction of materials of Class "B" has opened a wider choice to designers, and many are availing themselves of the advantages to be obtained from the use of these products. Materials of Class "B" have, in fact, been found satisfactory for receptacles, bases, and covers, permitting of the production of complete assembled parts in the same material. Tn European countries, there has been a very marked move- ment in favor of materials of Class "B" for the production of these parts, while in the United States the tendency, though more gradual, would seem to indicate their favorable consideration among many of the leading manufacturers of electrical ap- pliances. The designer may, therefore, safely follow his own judgment, selecting materials of Class "D" if he desires to be conservative and follow in the lines of established practice, or by selecting materials of Class "B" if he desires to avail himself of the greater accuracy and consequent reduced assembly difficulties offered. PLATE XVIII ILLUSTRATIONS 171 Plate No. XVIII. ATTACHMENT PLUGS AND PARTS Until very recently these parts have been made of porcelain r or where a tougher material was required, of Class "A" pro- ducts. At present, however, materials of Class "B" offering, as- they do, the heat-resisting qualities of porcelain with the tough- ness of Class "A" products, are also very extensively used. To a limited extent, owing to their comparatively high cost, materials of Classes "G" and "E" are also used. In fact, the choice between Class "D" and Class "B" ma- terials would seem to be a matter of individual preference, both being considered satisfactory, with a growing tendency in favor of the latter. 172 MOLDED INSULATION LABORATORY TESTS In describing the various classes of molded insulat- ing materials and their properties, relative values have been considered only in the abstract, while in the chapter covering the selection of materials and illustrating -typical molded parts, a more definite attempt has been made to distinguish between the classes, and to establish their individual merits for specific purposes 011 the basis of results obtained and present day usage in the electrical industry. As far as possible, reference to definite laboratory tests has been avoided, as liable to be misleading, partly due to a want of standardized methods in testing molded insulating materials, but principally due to variations in the quality of raw materials and methods of manu- facture. Practically all published information available, up to the present, has been obtained from manufac- turers of the various molded insulating products, or at best, from tests made on samples furnished for this specific purpose. Comparisons based on such data are seldom conclusive and cannot, therefore, be considered a safe guide in determining the most suitable insulat- ing product to be specified for any particular purpose. In fact, it is generally accepted, among electrical engi- neers, that they must depend on their own tests, though Ihey are most often governed by the more practical con- LABORATORY TESTS 173 sideration of length of service and reliability established by common experience. Owing to their scientific and general interest, how- ever, the author has felt that laboratory tests should be accorded a place in this work. In order to render such tests as nearly as possible comparative, commercial samples of the more generally manufactured insulating products have been procured rather than special samples prepared with a knowledge of the purpose for which they were required. The results given do not, therefore, cover all of the products of the classes of materials tested, as these would show wide differences due to variations in methods of preparation, quality of binders and fillers used, and conditions of manufacture. It follows in some instances that, as has already been stated, the reverse of con- clusions based on such tests would hold where products, seemingly inferior under the laboratory test, would prove superior for practical purposes of service. In the tests which follow, reference has, in some cases,, been made to two or three products of the same class indicated by the letters a, b, etc. This has been done to demonstrate the wide range of results that may be obtained from different commercial products manu- factured on the same general principle and in the same class of material. Materials of Classes "D," "B," "F," "H" and "I" being more generally known and understood, it has not been thought necessary to give them a place in these tests which are confined to the more recently introduced materials of Classes "A," "B," "C" and "G." All of the figures given have been prepared under the personal supervision of Mr. F. M. Farmer, of the 174 MOLDED INSULATION Electrical Testing Laboratories of New York. In some cases, the form of test has been suggested by the author to, as nearly as possible, approach prac- tical conditions as met in his own experience. DIELECTRIC STRENGTH TESTS 175 DIELECTRIC STRENGTH TESTS These tests were made with samples of the following shapes and obtained as follows : Class "A." Plates 2%"xl7 s "xi/ 2 " cut from molded plates 6"x4:"xy:>". Class "A" (a). Molded bushing, irregular shape, 3"x 2%" over all. Class "B." Cover, over all, dimension 2%"x2%"x 1%" high, width, i/ 2 " wall. Class "B" (a). Caps for hexagonal nuts or bolts, maximum width of head, 1", thickness of wall, %". Class "C." Plates 3}i"x2% w x5/16" thick, cut from one plate 5"x7"x5/16". Class "C" (a). Plates 3"x3"x%" cut from one plate 7"x7"x%". Class "G." Plates 4"x2%"x%" cut from one plate 8"x6"xV 2 ". Class "G"(a). Plates 4"x2%"xi/ 2 " cut from one sheet 8"x8"xy 2 ". Class "G" (b). Molded bushing l% ir xl% w over all. The dielectric strength tests were made with the sample placed between blunt needle points; voltage was applied to the needle points at a low value, and gradually 176 MOLDED INSULATION increased, until puncture occurred. The high tension voltage was measured by means of a voltmeter connected across the low tension winding of the transformer, the ratio being known. The current was obtained from a 60 cycle course, the wave form of which is practically a sine curve. TESTS 177 SAMPLE TESTED AS RECEIVED Class "A" Specimen No. 1 Specimen No. 2 Specimen No. 3 Class "A" (a) Specimen No. 1 Specimen No. 2 Specimen No. 3 Class "B" Specimen No. 1 Specimen No. 2 Specimen No. 3 Class "B" (a) Specimen No. 1 Specimen No. 2 Specimen No. 3 Class "C" Specimen No. 1 Specimen No. 2 Specimen No. 3 Class "G" Specimen No. 1 Specimen No. 2 Specimen No. 3 Class "G" (a) Specimen No. 1 Specimen No. 2 Specimen No. 3 Class "G" (b) Specimen No. 1 Specimen No. 2 Specimen No. 3 Volts Per Mil. 152 17S 143 361 350 353 91.8 83.5 88.0 167.0 148.7 i59.a 69.5 72 ^ 70.8 46.2 41.7 45.0 221 213 218 326 315 333 178 MOLDED INSULATION SAMPLES TESTED AFTER IMMERSION IN WATER TOR 72 HOURS Class Specimen No. 1 Specimen No. 2 Specimen No. 3 Class "A" (a) Specimen No. 1 Specimen No. 2 Specimen No. 3 Class <'B Class "B Class "C" Class "G> Specimen No. 1 Specimen No. 2 Specimen No. 3 (a) Specimen No. 1 Specimen No. 2 Specimen No. 3 Specimen No. 1 Specimen No. 2 Specimen No. 3 Specimen No'. 1 Specimen No. 2 Specimen No. 3 (b) Specimen No. 1 Specimen No. 2 Specimen No. 3 Volts Per Mil. 114 110 103 287 293 301 53 58 55 121 118 107 42 40 45 40 ' 36 38 235 228 241 TESTS 179 SAMPLES TESTED AFTER IMMERSION IN TRANSFORMER OIL AT 75 C. FOR 72 HOURS Volts Per Mil. ^Class "A" Specimen No. 1 152 Specimen No. 2 170 Specimen No. 3 1C4 Class "B" Specimen No. 1 193 Specimen No. 2 169 Specimen No. 3 188 Class "C" Specimen No. 1 145 Specimen No. 2 149 Specimen No. 3 147 \ Class "G" Specimen No. 1 30.3 . Specimen No. 2 29.8 Specimen No. 3 31.0 Class <-'G" (a) Specimen No. 1 180 Specimen No. 2 184 Specimen No. 3 180 *NOTE Samples blistered and were slightly deformed after test. 180 MOLDED INSULATION SAMPLESJTESTED AFTER SUBJECTION TO ^ TURE OF 100 C. FOR 12 HOURS TEMPERA- 'Class "A Class "B Class Class "G Class (a) Specimen No. 1 Specimen No. 2 Specimen No. 3 Specimen No. 1 Specimen No. 2 Specimen No. 3 Specimen No. 1 Specimen No. 2 Specimen No. 3 Specimen No. 1 Specimen No. 2 Specimen No. 3 Specimen No. 1 Specimen No. 2 Specimen No. 3 Volts Per Mil. 87.7 91.1 86.0 90.0 84.0 91.0 70.0 730 65.7 67.0 63.0 163.5 159.6 166.0 *XOTE Samples blistered and were slightly deformed after test. TESTS 181 SAMPLES TESTED AFTER SUBJECTION TO A TEMPERA- TURE OF 200 C. FOR 12 HOURS *Class "A Class Class Class ^Class "G Specimen No. 1 Specimen No. 2 Specimen No. 3 Specimen No. 1 Specimen No. 2 Specimen No. 3 Specimen No. 1 Specimen No. 2 Specimen No. 3 Specimen No. 1 Specimen No. 2 Specimen No. 3 Specimen No. 1 Specimen No. 2 Specimen No. 3 Volts Per Mil. 67.0 60.0 62.0 98.0 10S.O 96.0 74.0 79.0 76.0 102.5 109.0 iui.o 119.0 116.0' 1240 ^NOTE Samples were swollen up after test and entirely deformed. Samples were blistered and slightly deformed after test. 182 MOLDED INSULATION SAMPLES TESTED AFTER SUBJECTION TO A TEMPERA- TURE OF 300 C. FOR 12 HOURS Volts per Mil. *Class "A" Specimen Xo. 1 Specimen No. 2 ... Specimen No. 3 Class "B" Specimen No. 1 96 Specimen No. 2 105 Specimen No. 3 102 Class "C" Specimen No. 1 94 Specimen No. 2 , 90 Specimen No. 3 96 *Class "G" Specimen No. 1 Specimen No. 2 ... Specimen No. 3 ... *Class "G" (a) Specimen No. 1 Spe'cimen No. 2 ... Specimen No. 3 ... *NOTE Unable to test because of change caused by heat. TESTS 183 SAMPLES TESTED AFTEE SUBJECTION TO A TEMPERA- TURE OF 300 C., COOLING AND THEN SUBJECTING TO IMMERSION IN WATER FOR 24 HOURS f Class Class "B Class ^Class "G *Class (a) Specimen No. 1 Specimen No. 2 Specimen No. 3 Specimen No. 1 Specimen No. 2 Specimen No. 3 Specimen No. 1 Specimen No. 2 Specimen No. 3 Specimen No. 1 Specimen No. 2 Specimen No. 3 Specimen No. 1 Specimen No. 2 Specimen No. 3 Volts per Mil. 80 78 83 55 57 54 'NOTE Not tested because of change caused by heat. 184 MOLDED INSULATION INSULATION RESISTANCE TESTS The samples submitted for this test were the same as those used for the puncturing tests. They were first used for measure- ments of the- resistance, and afterwards for the puncture tests. The insulation resistance was measured by the usual high sensibility series galvanometer method, the time of electrification being one minute. Voltage of 150 and 700 volts were employed, depending upon the value of insulation resistance to be measured. The electrodes employed were containers. A guard ring was employed so that the question of surface leakage was thereby eliminated. When the immersed samples were withdrawn from the water, the excess surface moisture was removed with blotting paper. Since the samples were very small and the guard ring near the edge, it is probable that the leakage current was relatively large and the result must be considered of questionable value. TESTS 185 SAMPLES TESTED AS RECEIVED Insulation resiatance megohms per inch, cube Class "A" Specimen No. 1 235,710 Specimen No. 2 60,700 Specimen No. 3 174,200 Class "A" (a) Specimen No. 1 Greater than 1,000,000 Specimen No. 2 " " 1,000,000 Class "-B" Specimen No. 1 Specimen No. 2 Specimen No. 3 21,300 18,070 12,300 Class "B" (a) Specimen No. 1 Specimen No. 2 51,200 40,700 Class "0" Specimen No. 1 Specimen No. 2 Specimen No. 3 290,000 115,000 240,000 Class "C" (a) Specimen No. 1 Specimen No. 2 24,900 28,100 Class "G" Specimen No. 1 Specimen No. 2 Specimen No. 3 65 93 76 186 MOLDED INSULATION SAMPLES TESTED AFTER IMMERSION IN WATER FOR 72 HOURS Insulation resistance megohms per inch, cube Class "A" Specimen No. 1 Specimen No. 2 Specimen No. 3 513 890 1070 Class "A" (a) Specimen No. 1 Specimen No. 2 800,000 600,000 Class "B" Specimen No. 1 Specimen No. 2 Specimen No. 3 470 380 710 Class "B" (a) Specimen No. 1 Specimen No. 2 14,300 17,210 Class J'O" Specimen No. 1 Specimen No. 2 Specimen No. 3 900 1,320 1,150 Class "0" (a) Specimen No. 1 Specimen No. 2 21,110 19,000 Class "G" Specimen No. 1 51.0 Specimen No. 2 Specimen No. 3 40.0 42.0 Class "G" (a) Specimen No. 1 Specimen No. 2 Specimen No. 3 7,590 11,400 8,100 Class "G" (b) Specimen No. 1 Specimen No. 2 6,250 5,600 TESTS 187 SAMPLES TESTED AFTER SUBJECTION TO A TEMPERA- TURE OF 100 C. FOR 12 HOURS * Class "A" Class "B>- Class Class Class G" (a) Insulation resistance megohms per inch, cube Specimen No. 1 Greater than 1,000,000 Specimen No. 2 v " " 1,000,000 Specimen No. 3 " " 1,000,000 Specimen No. 1 Specimen No. 2 Specimen No. 3 25,800 36,100 30,400 Specimen No. 1 Greater than 1,000,000 Specimen No. 2 Specimen No. 3 Specimen No. 1 Specimen No. 2 Specimen No. 3 Specimen No. 1 Specimen No. 2 Specimen No. 3 1,000,000 1,000,000 1,790 2,310 3,840 250,000 340,000 376,000 'NOTE Samples blistered and warped slightly. 188 MOLDED INSULATION SAMPLES TESTED AFTER SUBJECTION TO A TEMPERA- TURE OF 200= C. FOR 12 HOURS 'Class "A" Class "B" Class "0" 'Class h *Class "G" (a) Insulation resistance megohms per inch, cube Specimen Xo. 1 Greater than 1,000,000 ( Specimen No. 2 " " 1,000,000 Specimen Xo. 3 " " 1,000,000 Specimen X T o. 1 Specimen Xo. 2 Specimen X T o. 3 350,000 405,000 341,000 Specimen Xo. 1 Greater than 1,000,000 Specimen Xo. 2 lt " 1,000,000 Specimen Xo. 3 " " 1,000,000 Specimen Xo. 1 Specimen Xo. 2 Specimen No. 3 850..000 970,000 680,000 Specimen Xo. 1 Greater than 1,000,000 Specimen No. 2 " " 1,000,000 Specimen No. 3 " li 1,000,000 *NOTE Samples blistered and swelled badly. **NOTE Samples blistered and swelled slightly. TESTS 189 TENSILE STRENGTH TESTS Samples for these tests were submitted in the form of standard briquettes used in cement testing. These briquettes were cut out of blocks about 1" thick of the respective materials. These tests were made in a standard tensile testing machine having a capacity of 4,000 Ibs. The jaws employed corresponded in design with the standard shape used in testing cement bri- quettes. SAMPLES TESTED AS RECEIVED Tensile strength.pounds per square inch Class "A" Class "B Class Class "G Class "G" (a) Specimen No. 1 Specimen Xo. 2 Specimen Xo. 3 Specimen Xo. 4 Specimen Xo. 1 Specimen Xo. 2 Specimen No. 3 Specimen Xo. 4 Specimen Xo. 1 Specimen Xo. 2 Specimen X T o. 3 Specimen Xo. 4 Specimen Xo. 1 Specimen Xo. 2 Specimen Xo. 3 Specimen Xo. 4 Specimen Xo. 1 Specimen Xo. 2 Specimen Xo. 3 Specimen Xo. -4 2,000 940 1,090 1,010 1,550 920 1,285 1,421 2,230 1,985 2,478 2,918 3,020 4,000 2,920 3,405 4,750 3,780 2,880 3,860 190 MOLDED INSULATION ARC TESTS The following samples were submitted for tests: Class "B" Molded piece of irregular shape I%"x2%"x 1 / 4 l over all. Class "C>- Molded block 4%"x2%"x2%' Class "C" (a) Molded block 5"x3"x%". Class "C" (b) Disc 4%"x%". Class "G" Block 3"xl"xl". Class "G" (a) Block 2%"xl%"x%". TESTS 191 TESTS (a) Sample held ] /4" above the flame of the arc for one minute. (b) Sample passed slowly through a part of the flame of the arc. (c) Sample held in the flame of the arc for one minute. (d) Sample ignited, when possible, and then held in the open air. (e) Sample carbonized when possible, and held across the extinguished arc, carbons still hot, to re-estab- lish arc. (f) Same as test "e," except carbons were first allowed to cool. 192 MOLDED INSULATION RESULTS OF TESTS Class "B" Test Result a. Became red hot and charred slightly. b. Charred, but did not catch fire. c. Became red hot and charred. d. Became red hot, would not burn. e. When carbonized was conducting. f. When carbonized was conducting. Class "C" Test Result a. No noticeable effect. b. Fused quickly to a glass-like sub- stance. c. Fused slowly. d. Would not burn. e. Non-combustible and non-conduct- ing. f. Non-combustible and non-conduct- ing. Class "C" (a) Test Result a. No noticeable effect. b. Fused slowly. C. - Fused slowly. d. Would not burn. e. Non-combustible and non-conduct- ing. f. Non-combustible and non-conduct- ing. Class "G" (b) TESTS 193 Test Result a. Charred slightly. b. Caught fire slowly. c. Caught fire and fused. d. Would not burn outside of arc. e. Fused portion was conducting. f. Fused portion was non-conducting. Class "G Test Result a. Caught fire slowly. b. Caught fire, but stopped on leaving arc. c. Caught fire and burned in air a little. d. Caught fire and burned in air a little. e. Charred and became conducting. f. Charred and became conducting. Class "G" (a) Test Result a. Caught fire instantly. b. Caught fire and continued to bum. c. Caught fire and charred. d. Caught fire and burned for about 1. minute. e. Charred and became conducting. INDEX. 195 Abrasive action 32 1 ' wheels 109 Accuracy, 18, 72, 89, 97, 119, 125, 13"4, 151, 159, 163, 165, 167, 169 Acetaldehyde 64 Acetone 44, 64 Acetylene 56 Acids, 12, 21, 22, 40, 47, 60, 6], 80, 82, 86, 107. 11 acetic 62, 83 ' ' benzolsulphonic .... 61 ' ' hydrochloric 13, 64 1 ' nitric 34 ' ' nitrous 63 ' ' organic 64 " proof... 20, 21, 24, 107 " resisting qualities, 21, 22, 107. 1 ' sulphonic 61 " sulphuric, 13, 31, 61, 63, 64, 80, 81, 83, 90. Adhesive qualities, 25, 26, 53 Adulterants 42, 49, 50 Africa 21, 43, 52 Air 22, 81, 191 Albumin 60, 62, 95 Alcohol, 42, 44, 51, 53, 57, 60, 62, 80. Aldehyde. . 56, 57, 59, 64 Alkalies 13, 21, 40, 47, 64, 107. ' ' caustic ... .83 Alkaline agents 86 compounds 90 ' ' earths 30 silicate 76, 77 Alumina, 21, 23, 24, 26, 27, 29, 34, 73. Aluminous materials. .. .10, 30 Aluminum silicate 24 Amazon tree . : 52 Amber 59, 83 Amboyna pine 45 Ammonia 59, 63, 64 Amperages 155 Amphibole 20 Amylalcohol 56 Aniline 64 Anhydrides 64 Animal oil 39 Animal products 41 Antophyllite . 20 Apparatus 85, 121, 161 Appearance, 19, 31, 32, 34, 37, 44, 68, 69, 71, 74, 79, 88, 102, 108, 109, 110, 125, 127, 129, 139, 141, 143, 155. Arc deflectors 106, 161 11 electric, 22, 74, 88, 91, 104 r 106, 107, 191. " tests 190 Arcing 89, 106, 161 Aromatic compounds 60 Artificial stone. . . 31 196 MOLDED INSULATION Asbestos, 9, 10, 20, 21, 22, 25, 26, 31, 32, 55, 58, 66, 68, 71, 72, 73, 74, 78. . . 88, 89, 103, 157. 1 ' compounds ..... 22 ' ' vulcanized 9 Asia 37, 41, 52 Asphalt, 10, 13, 17, 38, 39, 40, 42, 43, 48, 49, 50, 51, 66, 68, 71. ' ' ' artificial 39 ' < lakes 39 ' ' natural 39 ' petroleum 39 Assembling difficulties 169 Atmospheric condition 95 " exposure, 46, 50, 91. Atomic combination 87 Attachment plugs 171 Austria 38 Automobile work 132, 134 Barbadoes 39 Barrier 130 Bases 128, 165 Basket 38 Belgium 38 Benzaldehyde 64 Benzene 51, 60 Benzine 44, 46, 51 Benzol 44, 46, 51, 59, 62 Benzoline 51 Billiard 'balls 31 Binders, 7, 9, 10, 12, 14, 15, 16, 20, 22, 25, 30, 31, 32. 33, 40, 42, 46, 49, 66, 67, 68, 69, 71, 72, 73, 74, 78, 85, 88, 89, 91, 92, 99, 103, 107, 173 Binders, asphaltic 15 1 ' fireproof 26 " heat resisting 11 " hydraulic 74 " inorganic, 26, 30, 33, 73, 74. " organic, 7, 16, 21, 22, 32, 66, 69, 71, 73, 74, ' 84, 89, 106. " resinous, 15, 24, 90, 92 1 ' synthetic, 84, 85, 88, 89, 91, 99. Binding value 33 Bismuth 59 Bitumens 39, 40, 68, 69 Bituminous substances.... 38 Blast furnace slag 30 Blistering, 179, 180, 181, 187, 188. Blocks 79, 80, 130, 189, 190 Blood 11 Bobbins 14 Bone 59, 60 Box, fuse 122 " insulating. .120, 121, 122 ' ' switch 122 Breakage 163 Bricks 28 Brittleness 9, 40, 101, 155 Bromine water 63 Buffalo 28 Buffing 109 Burning 29, 30, 104, 192 Burrs Ill, 116, 127 Bushing 116, 175 Buttons . . 12 Calcination 27, 28 Calcium acetate . . 64 INDEX 197 Calcium aluminates 30 " bisulphite 35 ' ' carbonate 27, 64 " chlorate 13 ' ' chlorides 31 1 ' salts 64 tl silicates 30, 33 1 ' sulf ate 26 Camphor, 33, 34, 35, 79, 80, 81, 82. " oil 34 " synthetic 35 Camphoric acid 35 Canada 20, 21, 23 " dept. of mines 20 Caimabis sativa 37 Caoutchouc 52, 78, 83 Carbolic acid 60, 88 Carbon 38 " bisulfide 44, 62 ''< dioxide 27, 31 Carbonate of lime 30 Carbonic acid 58 Carbonizing 191, 192 Carborundum 109 Carteria lacca 41 Casein 12, 83, 84, 104 Catalyser '.57, 58 Catalytic nature 73, 86- Caustic alcali 83 Caustic soda 35 Celluloid, 14, 35, 37, 79, 81, 82, 83, 104. Cellulose. 14, 33, 49, 79, 80, 81, 94. Cement, 26, 27, 28, 29, 30, 31, 73, 120. " briquettes 189 " rock . 29 " testing 189 Cementing media Central America 52 Centrifuges 80 Ceramics, 16, 72, 75, 93, 104, 107, 120, 128, 134, 139, 141, 143, 151, 155, 157, 161, 163, 165. Ceresin wax 40 Chalk 30, 75 Charcoal 34, 42 Charring 104, 106, 155, 192 Chemical action 93 analysis 20, 71 compounds 90 China 33, 50 Chinese wood oil 50 Chipping 155 Chlorides 31 Chloroform 44, 53, 54, 62 Chromates 14 Classification 16 Clay 22, 23, 28, 29, 30 ' ' china 75, 76 ' ' fused 75 1 ' matter . : 27 Climatic action 31 " conditions, 18, 22, 42, 45, 68, 83, 95, 132. Closed dies Ill, 112, 114 Coal 28, -29, 40, 61 Coal tar 39, 51, 50, 61, 62 ' ' " colors 42 " " pitch 39 " " residues 39 Column dephlegmators. . . . 58 Color, 44, 71, 79, 81, 82, 108, 109. Coccus lacca 41 Components, basic 30 Condensation, 11, 60, 63, 64, 86, 87. 198 MOLDED INSULATION Condensation products, 60, 65, 86. process, 63, 65, 86 Conducting 192 Contacts 159 Copal 43, 44, 45, 51, 91 " resins 40 Copper 57, 58 Coral 83 Cotton 36, 37, 32, 80 " bags 42 Counterbored holes... 128, 130 Cover, insulating, 120, 121, 122, 151, 165, 169, 175. Cracking 155 Cresol 62 Crotonaldehyde 64 Crude rubber 52, 54, 55 Crystalline minerals 20 Crystallization 35 Cuba ; 39 Current 176,' 184 Damar Gum 45, 66, 68 Decomposition 49, 82 Deforming 102 Dental work 31 Design 102, 108, 119 Design, ideal 123 " incorrect 125 Deterioration 103 Dextrine 15 Diamidotriphenylmethan. . . 64 Dielectric strength, 9, 11, 24, 25, 40, 45, 55, 60, 91, 93, 98, 99, 102, 103, 139, 153, 163, 165, 175. Dies, 7, 10, 11, 12, 13, 14, 16, 17, 32, 66, 67, 72, 73, 74, 76, 83, 87, 88, 95, 100, 108, 109, 110, 111, 112, 113, 116, 118, 132, 149 " closed Ill, 112, 114 11 open Ill, 112 Dimethylamin 59 Dinaphthol ' 64 Discs 112, 190 Disintegration 10, 102 Dissolving properties 51 Distillation 34, 44 Distorting 134 Draw 123, 129, 130 Drawings 97 Driers 48 Drilling 100 Drums, rotating 76 Drying oils 49, 50 li process 71 1 ' qualities 50 Durability 31 Dye 42 11 stuffs 59, 66, 79 Eau De Javelle ........... 63 Ebonite ............... 55, 83 Ebony ................... 83 Efficiency ................ 110 Egypt ................. 36, 39 Elasticity. .35, 54, 78, 82, 101 Electrical apparatus. .. .7, 105 " appliances ..... 7 Electric controllers ........ 161 fans ............. 167 " motors .......... 167 " signaling appar- atus ........... 163 Electrical Testing Labora- 174 INDEX 199 Electrified 82 Emery wheels 31 Engines, hot . 132 England 12 Ether 44, 46, 62, 81, 82 Ethyl alcohol 51 Ethylene 56 Europe 5, 12, 37, 153 Evaporative qualities 50 Expansion 153 Fans, electric 167 Fats 39 Feldspar 25, 30, 75 Ferrichloride 63, 64 Ferrous oxide 21 Fibre, 7, 9, 22, 32, 35, 36, 37, 38 90, 91, 95, 99, 100, 101, 104, 106, 130, 153, 155, 165, 169. Fibre products 17, 90, 100 11 vulcanized 90, 155 Fibrine 11, 12 Fibrous substances 87 " sheets 91 Fig trees 41 Filler, 7. 9, 10, 12, 14, 16, 21, 25, 31, 33, 35, 37, 66, 67,- 68, 69, 71, 72, 73, 74, 87, 88, 98, 99, 103, 105, 173 " inorganic, 16, 17, 31, 55, 71, 78, 83, 87, 89, 106. 11 organic, 31, 71, 78, 83, 87, 89. Finishing 141, 143 Finishing treatment 116 Fins Ill, 127 Fireproof 18, 20, 104 Fireproof coating 26 Fireproof material 9 Fire resisting 85 Fire-resisting qualities 22 Fire Underwriters 153 Firing... 23, 72, 76, 77, 96 Fixtures, lighting 105 Flames 82, 88, 91, 104, 191 Flat irons 159 Flax 32, 37, 38, 48, 80 Flexibility, 22, 24, 32, 35, 78, 101. Flint 23, 25, 31 Floorings 31 Florida 22, 36 Flowing qualities 128 Fluxes 23, 75 Flux material 25 Fluxing action 30 Formaldehyde, 11, 14, 56, 57, 58, 59, 60, 63. 65, 83, 86. Formalin 57, 58, 59 Formic acid 56, 57, 58 Formosa . 34 Fossil gums 43 France 38 Fusing 106, 192 Fuse box 122 Fusible solid 86 Fusing point. 17 G Gabon 44 Galvanometer 184 Gasoline vapors 132, 133 Genus gossypium 36 Georgia 36 Germany 38, 153 200 MOLDED INSULATION Glass 75, 82 Glass-like substances 192 Glazing 108 Glue, animal 14 " cabinet makers... 14, 59 Glutinous substances.. . .12, 13 Glycerine 62 Grain alcohol 51 Grinding 120 Grinding machinery 29 Guard ring 184 Gums, 10, 43, 44, 59, 68, 103 1 ' alcohol soluble 52 ' ' resinous 94 Gun cotton 79, 81, 82 Gutta percha 17 Gypsum 75 Hardness 75, 82, 40, 44 Hard rubber, 5, 7, 9, 12, 54, 55, 59, 9ft, 100, 103, 107, 109. Heat resisting, 39, 41, 43, 45, 47, 49, 55, 78, 79, 84, 85, 86, 88, 89, 91, 92, 95, 101, 103, 107, 122, 145, 147, 149, . 155, 157, 159, 171 " " qualities, 11, 12, 15, 24, 25, 30, 40, 45, 48, 70, 79, 95. Heated press table 114 Heating appliances 159 ' ' elements 159 Heatproof, 83, 88, 89. 91, 104, 105, 133. Hemp 32, 37, 80 Hevea, plant 52 Hexamethylene-tetra-amine. 59 High finish 145 " polish.. 109, 116, 119, 145 " tension .70, 98, 176 Holes, counterbored.. .128, 130, Homogeneity, 76, 80, 90, 98, 99 Hoof 12 Hoof products 49 Horn 12, 83 Horn refuse 49 Hot engines 132 " oils 132 Household articles 157 Hyatt process 80 Hydraulic 115 cements, 10, 25, 26, 27, 30, 31, 33, 73. Hydrocarbon 47 Hydroextractor 81 Hydrogen 38, 58, 60, 64 Hydrosiljcate of alumina. . 25 Hygroscopic 62, 68, 95, 104 Ideal design 123 Igniting 82, 191 Illinois 28 Impregnating, 40, 45, 47, 48, 50, 99. Inaccuracy 96 Incorrect design 125 India 23, 39, 41 Indiana 28 " rubber 56, 59 Inflammability, 14, 70, 81, 82, 83, 84, 85. Infusible 86, 87, 88 INDEX 201 Insect 41 Inserts, 118, 119, 121, 132, 134 Insolubility 10, 82 Insulated knurls 125, 128 Insulated wires 151 Insulating 'box, 120, 121, 122, 151. Insulating cloth, 40, 45, 48, 50 tapes ....40, 48, 50 ' ' value 7, 24, 99 " varnishes, 13, 40, 43, 45, 50. Insulation, resistance 184 Insulator 78, 79, 102, 132 Insulators, resistance 77 Iron 24, 58 " oxide, 23, 24, 26, 27, 29 Isoprene 56 Italy 20 i Japan 33 ' ' camphor 33 Java 7 43, 45 Kauri : 44 Kerosene oil 59 Keones 64 Kieselguhr 26 Kiln 28, 30, 75, 76 Knife 42 Knurling, 126, 127 " braided 127 " straight 127 Komppass synthesis 35 Kristallviolet , . 59 Laboratory tests 173 Lac 41, 42 ' ' crude 41 " button 42 f i garnet 42 < ' lake 42 " seed 42 " stick 41 Lamp black 66 Lapis 83 Laurus camphora 34 Lava 76 Lavite 75, 105 Lettering .120 Lighting fixtures 105 Lime, 21, 23, 26, 29, 30, 34, 39, 66, 73. 11 compounds 10, 33 Limestone. . .23, 27, 28, 29, 30 Lime water 59 Linaceae 38 Linoxen 48, 49 Linseed oil 48, 49, 50 " " boiled 48 Lint 36 Lirium Usitatissimum ...... 38 Literature 11, 86 Litmus 62 Low tension 72, 176 M Machining 130 Magnesia, 21, 23, 24, 26, 30, 31, 66, 71, 73. " cements 31, 33 " compounds ..31, 33 Magnesium carbonate . . 27, 30 " chloride 31 " oxide . . 24 202 MOLDED INSULATION Magnesium oxychloride. ... 31 11 .silicate, 20, 24, 33 Magneto insulator 132 Malachite 83 Manganese 24 Manilla 44 Marble 7, 31, 83 " waste 14, 31 Marl 29, 30 Mechanical advantages. .. .161 ' ' mixture 32 stability, 163, 165, 167. strength, 18, 19, 22. 32. ' ' suitability .... 165 Megohms. . .185, 186, 187, 188 Melting point, 35, 40, 42, 44, 47, 62, 69, 107 Mercury 59 Mercury bichloride 59 Metal contacts 159 ' ' covers 121 inserts, 118, 120, 127, 147 " parts, 12, 21, 43, 97, 100. 121, 130, 132, 134, 141, 145, 151, 153, 155, 157, 163, Metamorphosis 30 Methan 58 Methanal 56 Methylalcohol. . .51, 56, 57, 58 Methylaldehyde 56 Methylenitan 59 Mexico 39 Mica, 7, 10, 23, 24, 25, 26, 42. 92, 99. " built-up, 24, 52, 91, 107 1 < flake 99 ' ' insulator 25 " molded 18, 92, 136 refuse Micanite segments 13H Milk, curdled 83 Mineral fibre 15, 20, 32 filler 14, 33 ." oils 50, 61 1 ' pitch 40 11 substances 9 Mines 21 Mixing machine 66, 67 Moisture, 10, 12, 21, 22, 68, 69, 72, 74, 83, 89, 95, 102, 103, 104, 155. 184. Molds, 7, 10, 11, 16, 110, 111, 115, 117, 120, 125, 147. Mortar 33 Motors, electrical 167 Mozambique 44 N Naptha 51, 54 Napthol. 64 Natural cements 28, 29 Xeufuchsin 59 New York Electrical Test- ing Laboratories 174 New York State 27 New Zealand 38, 43 Nickel 58 Nitric acid ..80, 81, 83 Nitro cellulose... 35, 79, 80, 81 " industry . . . .' 35 Nitrogen 38, 79 Non-absorbent 74 Non-combustible 192 Non-conducting 192 Non-hygroscopic 68, 102 Non-inflammable 84 North Carolina 36 Numbering 120 INDEX 203 Oil 9, 17, 24, 34, 45 Oils, hot 132 Oil, transformer 179 Oil vapors 132 Oklahoma 37 Open dies Ill, 112 Opening material 25 Orange Shellac 42 Organic fibres 95 material, 12, 25, 52, 88, 98, 99. " solvents 90 Ovens 13 Overheating 167 Ox blood 11 Oxidation 57, 58 Oxides 31 Oxychloride 31 Oxydizing agents 48 Oxygen 25, 48, 51, 64 Ozokerite . . 40 Papaver somniferum 50 Paper 13, 17, 90 " insulating 37, 169 Paper machine 10 ' ' tissue 80 ' l satin 81 Papier mache 13 Paraffine 14 ' ' hydrocarbons .... 40 11 wax 47 Paraf ormaldehyde 57, 58 Parafuchsin 59 Patent flooring 31 1 ' literature 49 Patents 11, 48 Pennsylvania 28, 29 Pestles , 41 Petroleum 50, 51 Phenol, 11, 59, 60, 61, 62, 63, 64, 65, 86. ' ' formaldehyde, 36, 85, 87, 89. Philippine Islands 37, 43 Photography 59 Physical attributes 163 ' ' changes 13, 33 1 1 function 32 ' ' inertness 25 qualities 139 i ' structure . . 33 Pigments 66, 79 Pine tree 46, 51 Pins 116, 130 Pitch 39, 40, 42, 66 Plantation rubber 53 Plastic binders 87, 88 Plastic mass 7 11 material 73, 80, 82 Plasticity, 73, 76, 81, 82, 87, 88, 132. Plates 79, 175 Plugs, attachment 171 Polish, 108, 109, 116, 119, 120, 143, 143. Polymerization 56, 57, 58 Porcelain, 22, 25, 30, 43, 70, 72, 75, 76, 77, 93, 96, 98, 99, 101, 104, 123, 125, 139, 155, 161, 169, 171. " hard 75 Portland . 28 204 MOLDED INSULATION Portland cement, 23, 28, 29, 30, 31, 73, 74. " cement mill 29 " stone 28 Potash 23, 26, 62 Potassium 24 " bisulphite 61 Press 115, 117 Press table 1.14 Properties 172 1 ' chemical 68 < ' dielectric 102 < ' electrical 135 " insulating, 69, 72, 98, 132, 134. " mechanical, 7, 74, 135. " molding . . .11, 135 physical, 7, 21, 45, 54, 72, 74, 78, 135. Proprietory plasters 31 Publication 20 Punching 100 Puncture 70, 98, 176, 184 tests 97, 184 Puzzolans 27 Pyroxylin . . .35, 81 Quartz 25, 75 Eaised letters 120 Eeceptacle box 123, 169 Eefractory material 25 Eeinf orcing 24 Eesilient 100, 101 " artificial 86 Besin oils 44, 45 Eesinous binders, 11, 33, 24, 51 - " bodies, 42, 43, 49, 48, 51. ' ' materials 87 " substance, 11, 12, 59, 86, 91. nature 91 Eesins, 13, 41, 42, 43, 44, 45, 46, 48, 49, 50, 51, 52, 64, 66. Eesistance insulation 184 " insulators 106 ' ' test 184 Bings 136 Eiveting 100, 120 Bock 27, 28, 29 Bods 17, 79, 97, 136 Boilers 41, 42, 53, 80 " calendering 81 Bope 38 Bosendale 27 Eosin, 10, 42, 43, 46, 47, 50, 51, 66, 68, 69. " oil 49, 50 'Eotary kiln 29, 30 Bubber, 9, 17, 40, 49, 52, 53, 54, 55, 56, 78, 87, 89, 94. 1 ' artificial 56 " compounds, 17, 94, 98, 101, 103, 105, 109, 131, 132, 141, 143, 147, 155 " hard, 55, 99, 100, 103, 107, 109. ' ' substitutes 49, 55 " synthetic 56 " trees 52, 53 ' ' vulcanized 55 Bussia 20, 38, 39 INDEX 205 s Saccharine substances 59 Sample pieces 110 Sand 23, 25, 33, 66 Sap 41, 46 Saturating qualities 40 Saw dust 31, 33 Screw heads 120 " holes 125 Sea island cotton 36, 37 Sealing wax 43, 66, 120 Secrecy 8 Seed 36 Separators, arc 161 Serpentine 20, .21 Service conditions 147 Shale 29 " oils 47 Sheets, 10, 11, 13, 17, 23, 24, 33, 66, 79, 82, 90, 97, 130, 136. celluloid ....... 80, 82 ' ' fibrous 91 ' ' mica 107 Shell tortoise 83 Shellac, 9, 11, 12, 25, 41, 42, 47, 48, 49, 52, 66, 68, 69, 70, 85, 86, 91, 94, 98, 107. ' ' compounds, 5, 9, 10, 11, 87, 89, 94. substitutes, 47, 83, 86 ' ' varnishes 52 Short circuiting. .. 70, 102, 147 Shrinkage, 23, 53, 71, 72, 76, 77, 96, 127, 153. Siberia 23 Sierra Leone 44 Signal parts 163 Silica, 10, 16, 21, 23, 24, 25, 26, 27, 29, 71, 73. ' ' fused 75 Silicates 10, 20, 24, 26, 33 Silicious material 30 Silicon 25, 26 Silver 59 Silver salt 59 Sine curve 176 Slaked lime 26 Slate, 7, 14, 76, 165 ' ' waste 14 Soapstone 15, 75 Soap works 59 Soda 23 Sodium 24 " carbonate 80 ' ' hydrate 26 " silicate 26, 76 ' ' sulfide , . 35 Softening 10, 106, 157 Soja bean oil 50 " " tree 50 Soluble silicate 26 Solubility 35, 44 Solvents, 13, 34, 45, 48, 50, 51, 62, 69, 71, 79, 90. South Africa 20 " America .. 43, 52 ' ' Carolina 36 Spinning 36 Stamped metal 169 Starch 15, 49, 56, 59 Steam 34, 115, 116 1 < tables 66 1 i process 54 Stearic acid 39 Stearine pitch 39 Steel HI Stick lac 41 Stinging nettle 37 Strain 101 ' < insulators . . . . 130 206 MOLDED INSULATION Straw 32 Strength 32, 75, 100 1 ' mechanical, 18, 19, 22, 78, 99, 101, 102, 106, 129. " tensile 101, 189 Strengthening medium 78 Stress, mechanical 102 Structure. .20, 21, 22, 23, 32, 33 Sublimation 34 Substance, horny 13 Sulphur.. 12, 17, 38, 53, 54, 55 Sumatra 45 Sun ray 68, 69 Switch base 169 " box 122 " handles 153 Switzerland 38 Synthetic resinous materials, 11, 17, 63, 94, 99, 101, 103, 105, 123, 131, 139, 141, 143, 147, 149, 151, 153, 155. Talc 26 Tanneries 59 Taper 123, 129, 130 Tapes 40 Tapping 100 Tar oil 61 Telephone receivers 12 Tensile strength 101 " testing machine.. . .189 Terpenes 34 Tests, 172, 173, 175, 177, 178. 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192. " arc 190 ' < puncture 184 lt resistance 184 Tetramethyl diamidodi- Dhenylmethan 59 Textile . 42 Thin walls 121, 130 Third rail insulators 163 Threading 100, 127 Tools 12, 107 Tortoise shell 83 Toughness, 32, 45, 78, 82, 100. 155. Transformer 176 " oil ...179 Transparent 82 Trinidad 39 Trioxymethylene 57, 59 Tubes 17, 55, 97, 136 Tung oil 50 Turf 15 Turpentine 44, 46, 51, 56 Tvrosin . . 60 Underwriters 70, 104 Unglazed 102 United States, 23, 29, 36, 38, 153, 169. Upland cotton : 36 Urticacea? 37 Vapors 132, 133 ' ' gasoline 132, 133 oils ...133 Variation 97, 119, 125, 155 Variation 97, 119, 125 Vats 27 Vegetable fibres, 15, 32, 33, 36, 37, 90, 95. INDEX 207 Vegetable filler 14 ' ' gluten 15 " oil 39 ' ' substance 41 ' ' waxes 14, 15 Venezuela 39 Volcanic origin 27 Voltages 69, 70, 175 Voltmeter 176 Vibration 107, 134 Virginia 37 Vitrification 28 Vulcanization 10, 53, 54 Vulcanized fibre 36, 37, 90 " products 107 W Wall box 123, 169 Walls 123 Warping 107 Water, 10, 17, 22, 24, 26, 34, 35, 38, 40, 41, 42, 44, 52, 62, 64, 68, 73, 76, 80, 81, 82, 84, 86, 89. 91, 102, 103, 106, 115, 116, 178, 183, 186. Waterglass 26 Waterproof, 9, 18, 24, 89, 102, 103, 104, 155, 163 Waterproofing media 72 Waxes 51 Wax, sealing 120 Weather conditions. .. .69, 163 West Indies 36 Wheels, abrasive 109 Wild rubber 53 Wood, 7, 9, 35, 60, 61, 99, 100, 130, 153. alcohol 51 < < fibre 35 forms 13 " pulp, 11, 12, 31, 32, 35, 88, 89. Ying-tzu-tung 50 Zanzibar 44 Zinc compound 31, 58 " chloride 30, 64 ' ' chloride solution 30 ' ' oxide 30 ' ' oxychloride 31 UNIVERSITY OF CALIFORNIA LIBRARY BERKELEY Return to desk from which borrowed. This book is DUE on the last date stamped below. ENGINEERING LIBHAr. MAY i ' LD 21-100m-9,'48(B399sl6)476 24194 IVERSITY OF CALIFORNIA LIBRARY