possible use i r improved woods AND WOOD-BASE PLASTICS IN THE FLPNITLPE INDUSTRY December 1944 No. R1482 UNITED STATES DEPARTMENT OF AGRICULTURE FOREST SERVICE FOREST PRODUCTS LABORATORY Madison, Wisconsin In Cooperation with the University of Wisconsin PCSSI3L3 US::5 OF IhPROViD '.'CODS AITS ' T COD-3AS3 PLASTICS I IT Tr3 ?'JR1~ITIIR5 IITTUSTRY- By ALFRZD J. STAMM, Chemist Recent publicity on various improved woods and plastics has raised the question in the furniture manufacturer's mind as to the possibilities of usj ese materials in furniture. Much research and development by industry, 'oy the Forest Products Laboratory, an:", b" other research organi- zations is taking place and many significant adaptations and new products ve been developed. These products may have a definite place in cert- furniture parts, but probably wll] not be practical for use in furniture as a whole. The extent of their use will depend on the cost and the degree of increased serviceability. Although no definite figures on post- war costs can be determined at the present time, it is .'or some applications the increased cost will be small, while for others the increase in raw material and processing costs may be as much as threefold. In certain uses, however, this increased material and assembly cost will be partially offset by a smaller finishing cost. A brief review of the nature and properties of some of these new materials may aid the furniture manufacturer in de which of the r.ew products he might consider for use in the acture of his particular product. Inrpreg "Impreg" is the name given to the general of resin-im ted, uncompressed wood; that is, wood thai s be< ■ tod wi1 enolic or urea resin— forming systems under conditions sue/ • resin is formed thrc intimate structure of the wood. Under such c L1 ions con- limensional stability is imparted to the wood. Altho 1 lie rosins are more expensive than urea resins, th ' - Luco tfa equilibri bw I ling to about J>0 percent of normal in contrc^t with a reduction to 60 percent of normal obtainable with urea resins (Forest Products Laboratr: y-C or commercial products of similar charact ties). The urea resins, however, lo not iiscolor wood as do " enolic resins and • ' lake possible the obtaining of truer colors i t tl of treatment. "Published ' *food Products, Januu Home Furnie 1U5. Report No. Rl^g -1- The chief improvement in the properties of impreg over natural wood for use in furniture appears to be tho reduced swelling and shrinking and the accompanying reduction in checking and warping. Phenolic-resin treat- men'", also imparts appreciable decay and termite resistance and chemical resistance to wood. Although neither resin treatment gives fire resistance, incorporating f ire-retardant salts with the treating resin will give fire- retardant properties to the product. The only strength properties that are significantly increased by resin treatment are the compressive strength and the hardness, the latter of which may be increased from 50 to 100 percent. This is accompanied by a decrease in toughness. Data on v/ear resistance are still lacking. Veneer of almost all species can be used in the manufacture of impreg. !fith the exception of sapwood of readily treated species, however, solid wood in lengths greater than a foot cannot be adequately treated. In addition, the complete treatment of solid wood will be too expensive for the benefits gained. A surface treatment of solid wood does not improve the properties to the degree that might be expected. It appears, therefore, that resin treatment of wood for furniture will be largely confined to veneer and will not be used on solid wood furniture. The treatment of surface veneers, especially in the form of fancy crotches and burls, seems well worth while, due to the greatly reduced face checking resulting from the treatment. In matched, fancy, decorative veneers, which are often valued at 50 cents to S2 per square foot, the resin and treatment cost need not exceed 1 to 2 cents per square foot. Two panels, one with a phenolic-res in-treated crotch veneer face and the other with a matched untreated face, were held under normal room conditions at the Forest Products Laborator- for four years. A vast inn^rovement was noted in the treated panel; for the control contained many face checks, whereas the treated panel was free from face checks. Compreg "Comprog" is resin-treated wood that is compressed prior to the setting of the resin. The specific gravity can vary from that of impreg (about 15 to 20 percent greater than that of the untreated wood) up to 1,4. Compreg has improved properties similar to those of impreg plus a natural glossy surface finish and improved strength properties about in proportion to the compression. When compreg is compressed to a specific gravity of about 1.0 or greater, any cut surface can bo sanded and buffed to give a natural, durable, and solvent-resistant finish. The wood is finished throughout, and all that is needed to bring out the finish is making the surface plane. Scratches an-- 1 mars, therefore, which should only infrequently occur to comprog furniture because of its hardness, can be removed hy sanding m" buffing and the original finish restored without the necessity of applying a finish. Report Ho. H14S2 -2- Conprer; can "be made fro:.- soft, inferio:- species that aormally are not used for furniture a product obtained equal in appearance and in tost - 11 str*- properties to compreg made fron "birch or maple, 7 Lck laminated conpre,, will be too expensive, In general, for iture. I ..t :e \ , over, in special e: Lve furniture Blender legs are desired as a result o^" 11 Ly increased Lffness, Its greatest application appears to "be in face veneers. 'Then some of -ofter species arc used, partially compressed conpreg iultaneou8ly compresse untreated wood core in one operation without compressing the core. This is due to the fact treated faces ,-re plastic under heat prior to settin • of t r Jin and Trill, in some woods, compress to about one-half their o- 1 thick- ness under a pressure of only 200 pounds per Bquare inch, which pressure ises a : i jible compression of most dry wood cores. A harder surface Logree of natural finish can bo obtai 3 are atel ' compressed to a hi degr L \ an assembled wi1 i core. thod is used the con/' " to be sanded to give a ;oo lue bond. Compreg is susceptible to s certain dogroe o 'or dn rior to setting o resin in t facturing process. Fressin ; to contour of office and theatro seats is quite possible. Staypak "Staypak" is solid or lami wood cont Lnin no resin id the wood structure and is compressed to a specific r vity of 1.3 to 1.- under conditions such that it will not ten- to conditions. It is not so resistant to sv/olli . ahrj . 1 . is com r , but is more resistant than normal wood. It h s bur I Ln finish in contrast to I Lossy finish of compreg. It mi it b used for slender tabic logs as was sugg * for compreg would be considera"-: It could be used for table tops in both solid a. ' C . T\ st bilizing process darkens the wood to some o- . -.roods - or. the color of walnut an' some bocomin • rher. Tin >nly spocios be avoided for resinous pines. Like compreg, staypak U] jrades the inferior species; Cottonwood, basswood, and 'or, for example, give as beautiful ■ strong roduct as bird: or raaole. • Iroxylir. "Hydroxylin" or lignin Lc, as ti les c a : broTTi to blac'. *olyzed-wood plastj " ust or vrood chips in a moldin ; powder or lai t for . cost, water bance, anical properties »/ill depend to a large degree on at and nature of re r lasticizer, r- ■ Ln somt olic resin* A roduct wi1 ' properties Ho. ] '2 -3- is, however, made without the use of critical resin. Because of its dark color, its potential use in furniture manufacture would "be principally con- fined to use as a core material. The hydroly zed-wood sheets can "oe lami- nated with veneer or pigmented resin-treated paper faces. Its specific gravit" is about 1.4, similar to fully compressed compreg, staypak, and the paper-Dase plastics. Although it is not so strong as these other densi- fied materials, it has adequate strength for many furniture uses and should oe definitely cheaper. Paper-base Plastics Paper-base plastics have already "been used in furniture manufacture for tao'le and counter tops. Beautiful surface laminates with high water anr 1 acid resistance have been produced. Surfaces with linen-like appear- ance are being made entirely from paper-base plastics, using urea or melamine resins and pigmented paper. Since the war, high- strength paper-base plastics (papreg) have been developed with strength properties adequate for all kinds of furni- ture manufacture. This material can be laminated and molded to appreciable single- curvatures and moderate double curvatures under pressures as low as 50 pounds per square inch. Different colored and textured surfaces can be readily obtained. A cheaper paper plastic, suitable for core material, can be made by incorporating lignin recovered from the soda pulping process directly with the pulp in the beater, or impregnating the paper with the lignin solution. The addition of some phenolic resin improves the water resistance properties but would not bo essential for al! furniture uses. This laminate, like the hydroxylin, will be brown to black in color. '■Jhcre extreme curvatures are required, resin-bearing preforms of paper pulp can be first formed to approximate shape and then molded to the plastic state in metal dies or with bag-molding procedures. The product, like the paper-base plastic, is strong, tough and durable. One-piece drawers with rounded corners might, for example, be produced b^ this method. Summary Impreg, compreg, several forms of hydroxylin, various paper-base plastics including papreg and pulp preforms are now manufactured commer- cially. The hydroxylin alone is available for commercial use at the present time, duo to the critical resins used in the other products. Staypak and Uralloy arc not manufactured as yet, but several companies are considering commercial production. The furniture manufacturer v/ill thus not be ablo to take full advantage of these materials until after the '.'ar. Report No. R1482 _U_