THE GLUING CHARACTERISTICS CF 15 
 SPECIES CE WOOD WITH COLD- 
 
 SETTING, UREA-RESIN GLUES 
 
 April 1942 
 
 
 
 u 
 
 
 TTV 
 
 
 . *- 
 .942 
 
 
 THIS REPORT IS ONE CE A SERIES ISSUED 
 TO AID THE NATION'S WAR PROGRAM 
 
 No. 1342 
 
 UNITED STATES DEPARTMENT OF AGRICULTURE 
 
 FOREST SERVICE 
 
 FOREST PRODUCTS LABORATORY 
 
 Madison, Wisconsin 
 
 In Cooperation with the University of Wisconsin 
 
THE GLUING CHARACTERISTICS CF 1 3 SPECIES OF APOD 
 7JITH COLD-SETTING, UREA- RES IN GLUES- 
 
 By H. W. EICKrER, Junior Engineer 
 
 The study here reported was made to compare the gluing characteristics 
 of various species of wood when glued with cold-setting, urea-resin glues, 
 since it is known from previous studies— that there are considerable differ- 
 ences in gluing properties among species when gluing with other woodworking 
 glues. The species under test in this preliminary study are those which 
 appear to be of primary importance in war production work. Others may be 
 tested as the need arises. 
 
 It was the aim to conduct the tests in such a way that the results 
 could be compared with those obtained previously on the same species when 
 glued with casein glues.— 
 
 In addition, tests were made to see if there is any difference in the 
 gluing properties of the heartwood and sapwood of several of the species 
 when glued with urea-resin glues. 
 
 Method of Procedure 
 
 Species and Method of Selection 
 
 In this study, the following species were selected on the basis of 
 their importance at the present time: 
 
 ash, white hickory, pecan pine, southern yellow 
 
 basswood mahogany spruce, Sitka 
 
 birch, yellow maple, sugar sweetgum 
 
 Douglas-fir oak, red walnut, black 
 
 fir, noble oak, white yellowpoplar 
 
 —This mimeograph is one of a series of progress reports issued by the Forest 
 
 Products Laboratory to further the Nation's war effort. Results here 
 
 reported are preliminary and may be revised as additional data become 
 
 available . 
 
 2 
 
 -U. S. Department of Agriculture Bulletin I5OO, entitled "The Gluing of 
 
 Wood," by T. R. Truax. 
 Mimeo. No. 13*+2 -1- 
 
Both heartwood and sapwood of the 7 following species were selected 
 and glued separately to determine if there was any difference in their 
 gluing properties: 
 
 birch, yellow oak, red sweetgum 
 
 hickory, pecan oak, white yellowpopLxr 
 
 maple, sugar 
 
 Nominal 1-inch lumber was used for all species. The material was so 
 selected that the average specific gravity of each species was approximately 
 equal to the average for the species as- listed in U. S. Department of Agri- 
 culture Technical Bulletin ^79«^- Th e stock was then cut into pieces about 
 1 by 3 by 14- inches in size. The pieces were placed in a room where the 
 relative humidity was 65 percent and the temperature S0° F. , and allowed to 
 remain there until they had reached approximate equilibrium in moisture con 
 tent. The stock was then between 11 and 12 percent in moisture content. 
 
 The blocks of each species were weighed, arranged in order of their 
 weights, and the adjacent blocks wore then paired so as to have the blocks of 
 nearly the sane specific gravity glued together. As there were 4 glues being 
 used in this study, the pairs of blocks were divided into h groups having 
 similar ranges of specific gravity by selecting every fourth set for 1 glue 
 and in like manner for the other glues. 
 
 Just prior to gluing, the blocks were cut to a size of j/& by 2-l/2 
 by 12 inches and the faces planed smooth. 
 
 Glues and Gluing Co nd itio ns 
 
 Four commercial cold-setting, urea-resin glues in common use were 
 employed in gluing all the foregoing woods. The k glues were made by dif- 
 ferent manufacturers and were selected as representative of the better 
 brands of the cold-setting, urea-resin glues available. The glues were 
 mixed as directed by the manufacturers and spread with a small mechanical 
 spreader equipped with a rubber roll which was adjusted to deliver a spread 
 of between 20 and 25 grams per square foot. 
 
 Assembly periods (interval between spreading and pressing) of 5 an d 15 
 minutes were used to approximate a range commonly used in commercial opera- 
 tions. The gluing pressure was 150 pounds per square inch. This pressure 
 was allowed to remain on the blocks overnight, which gave a pressure period 
 of about l6 hours. The temperature in the gluing room and of the material 
 in the press was maintained between 75° and 80° F. 
 
 Four joints (20 test specimens) were glued at each assembly time for 
 each glue, which resulted in 32 joints per species, or &+ joints when the 
 sapwood and heartwood of the species were glued separately. 
 
 ^■"Strength and Related Properties of Woods Grown in the United States," by 
 L. J. Markwardt and T. R. C. Wilson. 
 
 Fimeo. No. 13*4-2 -2- 
 
After removal from the press, the glued blocks were placed in a 65 
 percent relative humidity room where they were allowed to condition for 1 
 week before being cut into test specimens. 
 
 Testing 
 
 k 
 Five shear specimens of conventional design— were cut from each 
 
 block. These specimens were broken in shear, the load at failure recorded, 
 
 and the percentage of wood failure estimated. 
 
 Results and Discussions 
 
 The results of the tests on joints of the various species, averaged 
 for the k cold-setting, urea-resin glues, are shown in table 1. For compari- 
 son, the results obtained in previous tests with casein glue are also shown. 
 
 The species were all well glued and, considering the percentages of 
 wood failure obtained, the joints made with the cold-sotting, urea-resin 
 glues appeared generally superior in quality to those glued with casein. 
 The average wood failures of the joints glued with the resin glues ranged 
 from S3 to 100 percent, while those glued with casein ranged from 30 to 99 
 percent. The better results obtained with the resin glues were most evident 
 on the species of higher specific gravities, such as sugar maple, red and 
 white oaks, white ash, and walnut. From this it appears that there is less 
 difference in the gluing characteristics of the different species when urea- 
 resin glues are used than when the gluing is being done with casein glues. 
 
 The average results, based on the U-. glues, for the different species 
 are shown graphically in figure 1. The species are arranged in increasing 
 order of their average specific gravities. Conforming with results of 
 previous experiments with other glues, _ the shear strength tends to increase 
 with an increase in specific gravity. From the detailed data also it 
 appears that within a species the denser specimens tend to produce the 
 higher test values. 
 
 The joint strength in hickory was abnormally low considering the 
 specific gravity of the wood and the amount of wood failure developed. rYhile 
 hickory showed the lowest wood failure (S3 percent) of all the species in 
 this study, it was still sufficiently high to indicate that higher joint 
 strengths might have been expected in view of its high specific gravity (O.7I) 
 
 Tho results obtained with each of the k resin glues on the 15 differ- 
 ent species are shown in table 2. There is very little difference in the 
 results obtained by using the various glues, but Glue B did show somewhat 
 less wood failure and shear strength values, especially in the denser 
 
 1+ 
 
 -Described in U. S. Department of Agriculture Bulletin I5OO and in Army, 
 
 Navy, and Federal glue specifications. 
 ?.*ineo. No. I3U2 -3- 
 
species. This glue had a tendency to "cake" together upon standing in the 
 container, with the result that it was hard to mix properly. Following the 
 start of the tests, this glue was removed from the market for a short time, 
 but has since been returned. 
 
 The data in table 3 indicate) that there is no consistent difference 
 in the results obtained with the 5" anc ^ l?- minute assembly times on the 
 different species and the averages for all the 15 species are identical 
 "</ r ithin those limits good joints can be obtained with urea-resin glues. 
 
 Heartwood and Sapwood 
 
 In table k the results of gluing the heartwood and sapwood are shown 
 for 7 species. Allowing for the differences in specific gravity between the 
 specimens of heartwood and sapwood used, only hickory showed a consistent 
 difference in strength and w-od failure between heartwood and sapwood. In 
 the case of sweetgum, the lower percentage of wood failure obtained with the 
 heartwood, as compared with bhe sapwood, is consistent with the higher shear 
 strength and specific gravity of the heartwood. Normally, of course, there 
 is no consistent difference in specific gravity between capwood and heartwood, 
 
 Summary 
 
 The results of tests on the gluing of 15 species of wood with k cold- 
 setting, urea-resin glues indicate: 
 
 In general, all the species tested can be glued with urea-resin glues 
 to produce joints as strong in shear as the wood itself. Hickory appears to 
 be somewhat more difficult to glue than the other species. In general, the 
 shear strength of the joints increased as the specific gravity of the woods 
 used in making the joint increased. 
 
 The average wood failures were generally higher on joints glued with 
 the urea-resin glues than were obtained previously on the same species glued 
 with casein glues. The wood failures of the resin-glued joints were fairly 
 uniform for all the species tested. This is in contrast with a general declin 
 in wood failures with an increase in specific gravity of the wood of casein 
 glued joints. 
 
 There was very little difference in the results obtained among the *4- 
 urea-resin glues used in this study, although one of the glues showed 
 slightly lower strengths and mod failures on the denser species. 
 
 Joints of essentially equal quality were obtained for assembly periods 
 of 5 and 15 minutes. 
 
 No significant difference in gluing properties was found between heart- 
 wood and sapwood in the 7 species compared with the possible exception of 
 hickory for which the heartwood appeared to be somewhat more difficult to 
 glue than the sapwood. 
 
 Mimeo. No. 13^2 -li- 
 
liable 1 .-- Comparison of the results of gluing 15 species 
 with cold-setting, urea-rv.sin and gasejg glu^s 
 
 
 
 Urea-reJ 
 
 Jin glues 
 
 A 
 
 Casein glues£. 
 
 Species 
 
 Speci- 
 
 AverageZ 
 
 Average- 
 
 Specific- 
 
 Averaged. 
 
 Average 
 
 • .r.. 4 
 
 Specific- 
 
 
 mens 
 
 . shear 
 
 wood 
 
 gravity 
 
 shear 
 
 wood 
 
 gravity 
 
 
 aver- 
 
 strength 
 
 failure. 
 
 of 
 
 Strength 
 
 failure 
 
 of 
 
 
 aged 
 
 
 
 wood 
 
 
 
 . wood 
 
 
 dumber 
 
 Lb. per 
 
 sq.in. 
 
 Pereent 
 
 
 Lb. per 1 
 sq.in 
 
 Percent 
 
 
 
 
 
 
 
 Ash, white 
 
 160 
 
 ; 2,265 
 
 96 ■ 
 
 0.59 
 
 • 2.S10 
 
 42 
 
 1 0.64 
 
 Basswood 
 
 1 160 
 
 1,441 1 
 
 97 1 
 
 .40 
 
 ■ 1,700 
 
 42 
 
 • .45 
 
 Birch, yellowZ. 
 
 320 
 
 2,S40 1 
 
 96 : 
 
 .61 
 
 2,6S0 
 
 1 40 
 
 .71 
 
 Douglas-fir. . . . 
 
 160 i 
 
 . 1,656 : 
 
 97 1 
 
 .49 
 
 ,1,800 
 
 £1,452 , 
 
 %9 
 
 1 ,.51 
 
 2.40 
 
 Fir, noble 
 
 160 1 
 
 . 1.632 
 
 9S : 
 
 .42 
 
 Hickory, pecun-2. 
 
 320 
 
 I 2,016 
 
 • S3 : 
 
 +11 
 
 2,SO0 i 
 
 63 
 
 : .66 
 
 Mahogany. ...*.. 
 Maple, sugar-2.. . 
 Oak, red^. . . . . . 
 
 160 
 
 1,924 
 
 99 
 
 .47 1 
 
 1,800 
 
 69 
 
 M 
 
 *+00 
 
 3,^25 
 
 66 
 
 .66 
 
 3,330 
 
 30 
 
 .66 
 
 320 
 
 2,258 
 
 94 
 
 • 61 
 
 2,370 
 
 56 i 
 
 .66 
 
 Oak, whiter. . . . 
 
 320 
 
 2,670 
 
 94 ■ 
 
 .6} 
 
 2,050 
 
 ^5 
 
 .68 
 
 Pine, southern 
 
 
 
 
 
 
 
 
 yellow 
 
 : 160 
 
 1,719 
 
 97 
 
 .51 
 
 1,950 
 
 S6 
 
 .61 
 
 Spruce, Sitka. . 
 
 160 
 
 . 1,306 
 
 93 
 
 •37 
 
 1,300 
 
 i 97 
 
 • 39 
 
 Sweet gum 
 
 . 320 
 
 1,769 
 
 ^1 ! 
 
 .51 ■ 
 
 1,790 
 
 76 
 
 •55 
 
 Walnut, black. . 
 
 : 160 
 
 : 2,393 
 
 : 9S 
 
 .51 
 
 2,150 
 
 53 
 
 •58 
 
 YellowpoplarZ. . 
 
 : 320 
 
 I 2,143 
 
 100 . 
 
 .50 
 
 1,600 1 
 
 S4 
 
 ; .45 
 
 —Results with 4 different resin gluee averaged. 
 
 2 
 
 —Results are taken from figure 13 in U, S. Department of Agriculture Bulle- 
 tin 1500, "The Gluing of Wood," by T. Et. Truax. 
 
 "^■Joints glued with resin glues conditioned to about 12 percent moisture con- 
 tent; joints glued with casein glues conditioned to about 7 percent 
 moisture content. 
 
 4 
 
 -Specific gravity based on the oven-dry weight and the volume at test. 
 
 ^Tleartwood and sapwood glood separately* 
 
 6 
 
 "Value recently obtained in stutiies of ^he gluing properties of noble fir, 
 
 but not reported in U. S. Department of Agriculture Bulletin I5OO. 
 
 h'imeo. No. 1342 
 

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Table 3-~ - Comparison of the results obtained with 5~ und 15-minutc 
 assembly times on 15 species with cold-sotting, ur^ a - 
 
 resin trlues 
 
 
 Average : 
 specific : 
 gravity 
 
 5-minut<- 
 
 : assembly : 
 
 15-niinute 
 
 1 assembly 
 
 Species 
 
 Average ; 
 
 Average : 
 
 Average : 
 
 Aver a 
 
 
 of wood : 
 usedi. : 
 
 shear : 
 
 wood : 
 
 shoor : 
 
 wood 
 
 
 strength: 
 
 failure ; 
 
 strength: 
 
 failure 
 
 
 
 Lb . pe r . 
 
 Percent : 
 
 Lb. per : 
 
 Percent 
 
 
 
 sq.in. 
 
 
 sq.in. ■ 
 
 
 Ash, white— . 
 
 O.59 
 
 2,29*4- 1 
 
 97 ■ 
 
 2.235 ! 
 
 93 
 
 Basswood— . . . , 
 
 .40 
 
 i.*3* 
 
 97 
 
 ijm 
 
 97 
 
 Birch, yellow 
 
 Douglas-fir— 
 
 .61 • 
 
 2,056 
 
 96 , 
 
 2,325 
 
 97 
 
 A9 
 
 1,692 
 
 97 
 
 1,630 
 
 97 
 
 Fir, noble— ■ 
 
 .42 : 
 
 1.634- . 
 
 93 
 
 1,630 
 
 93 
 
 Hickory, pecan : 
 Mahogany -^ 
 
 •71 
 
 2,059 : 
 
 34 
 
 1,994 i 
 
 33 
 
 •*7 1 
 
 1.933 
 
 93 
 
 1,915 : 
 
 99 
 
 Maple, sugar 
 
 .66 i 
 
 3. '411 
 
 34 : 
 
 3,44o 
 
 37 
 
 Oak, red. • 
 
 .63 
 
 2.314 
 
 95 i 
 
 2,204 
 
 93 
 
 Oak, white 
 
 .63 
 
 2,646 . 
 
 94 
 
 2,692 
 
 95 
 
 Pine, southern 
 
 yellow 
 
 Spruce , Sitka— 
 
 
 
 
 
 
 •51 
 
 • 1,795 ■ 
 
 97 
 
 i.7'+3 
 
 96 
 
 •37 
 
 1,306 
 
 9 H 
 
 • 1,312 
 
 92 
 
 Sweotgum 
 
 Walnut, blacki 
 
 .51 
 
 1,795 
 
 91 
 
 : 1.743 
 
 90 
 
 •51 
 
 2,369 
 
 93 
 
 2,416 
 
 99 
 
 Yellowpoplar 
 
 .50 
 
 2,151 
 
 99 
 
 : 2,135 
 
 99 
 
 Average result for 
 
 
 
 
 
 
 species tested. . . 
 
 : 
 
 : 2,112 
 
 ; 94 
 
 : 2,094 
 
 ; 9* 
 
 —Specific gravity based on the oven-dry weight and the volume at 
 
 approximately 12 percent moisturo content. 
 2 
 "Tost values are based on 30 specimens; for the other species the test 
 
 values are based on 160 specimens, except for sugar maple for which 
 
 the values aro based on 200 specimens. 
 
 DBO« So. 13 ! *-2 
 
Table 4. -- Re suits of gluing heartwood and sapwood of 
 of wood with cold-- setting, urea-resin 
 
 *■" & 
 
 lues 
 
 (Heartwood - H; Sapwood - S) 
 
 
 
 a 1 
 
 : Average— 
 
 : Average— 
 
 2 
 : Average— 
 
 Species 
 
 
 : shear 
 
 : wood 
 
 : specific 
 
 
 
 : strength 
 
 : failure 
 
 : gravity of 
 : wood used 
 
 
 
 :Lb.per sq.in. 
 
 : Percent 
 
 
 Birch, yellow 
 
 H 
 S 
 
 : 2.7S3 
 : 2,398 
 
 96 
 
 97 
 
 : 0.624 
 : .602 
 
 Hickory, pecan 
 
 H 
 
 S 
 
 I 1,^75 
 2,157 
 
 : SO 
 37 
 
 '. .709 
 .70'! 
 
 Maple, sugar 
 
 H 
 S 
 
 ! 3,445 
 
 : 3,404 
 
 59 
 : S2 
 
 i .664 
 .656 
 
 Oak, red 
 
 II : 
 S : 
 
 2,219 1 
 2,29S 
 
 94 
 
 94 
 
 .614 
 .64S 
 
 Oak, white 
 
 H : 
 S : 
 
 2,736 ! 
 
 2 , 602 : 
 
 93 
 96 
 
 .672 
 .592 
 
 Sweet gum 
 
 H : 
 S : 
 
 1,902 
 1,635 : 
 
 35 ! 
 
 3k 
 
 .536 
 .470 
 
 Yellowpoplar 
 
 H : 
 S : 
 
 2,092 : 
 
 99 : 
 99 : 
 
 .507 
 .503 
 
 —Each test value is the average of 160 specimens or more, glued 
 with h different resin glues. 
 
 2 
 
 —Specific gravity "based on the oven-dry weight and the volume at 
 
 12 percent moisture content. 
 
 Mimco. No. 1342 
 
UNIVERSITY OF FLORIDA 
 
 3 1262 08925 4253 
 
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