Chemical treatment of surfaces improves joints with certain woods and glues

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Material Information

Title:
Chemical treatment of surfaces improves joints with certain woods and glues
Physical Description:
4 p. : 21 cm.
Language:
English
Creator:
Forest Products Laboratory (U.S.)
Publisher:
U.S. Dept. of Agriculture, Forest Service, Forest Products Laboratory
Place of Publication:
Madison, Wis
Publication Date:
Edition:
Rev. Aug. 1953.

Subjects

Subjects / Keywords:
Gluing   ( lcsh )
Wood -- Bonding   ( lcsh )
Genre:
federal government publication   ( marcgt )
non-fiction   ( marcgt )

Notes

Additional Physical Form:
Also available online.
General Note:
Caption title.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 029723894
oclc - 61326152
Classification:
lcc - TA419 .U45 no.232 rev.1953
System ID:
AA00025043:00001

Full Text




TE C HNI C AL NOTE NU M BE R 232
UNITED STATES DEPARTMENT -OF AGRICULTURE FOREST SERVICE
FOREST PRODUCTS LABORATORY
MADISON 5, WISCONSIN RWEVISE 2 F A--it 93



CHEMICAL TREATMENT OF SURFACS, MPROV'EAJ
JOINTS.WITH CERTAIN WOODS -AND- GLUES


Most native American woods can be glued with most adhesives to produce joints as strong as the wood by the use of proper gluing conditions. However, certain species of high density or high extractive content are of ten not well glued even under good gluing practices.

In early tests at the Forest Products Laboratory, when wood surfaces were treated with chemical solutions before gluing, the quality of the joints was improved on several species with animal and casein glues. Treatment with a solution of caustic soda improved animal-glue joints on several wood species and the improvement was most Miarked under gluing conditions where starved joints normally occur. Caustic soda or lime water treatments also strengthened casein-glue joints in woods that
-ordinarily are joined with this glue with some difficulty.

The caustic soda solution consisted of 10 parts by weight of caustic soda and 90 Parts of water. The treatment consisted of brushing the solution onto the surfaces to be joined. After about 10 minutes the surfaces were wiped with a cloth to remove any excess solution or dissolved material and allowed to dry before being glued.

Treatment of woods with caustic soda solution or lime water in order to improve their glusbiity with the newer synthetic resin glues has not been adequately investigated. However, it does not appear that such treatment would be advisable, particula~rly with urea- and resorcinol -resin glues as any residual alkali on the wood surface might be expected to alter the catalyst systems in these glues and thus affect their curing, strength development, and durability. Experiments have indicated that good joints can be obtained on most native American woods with these resin glues without chemical treatment of the wood by proper control of gluing conditions.







Tests of Animal-glue Joints


The results of the tests on treated wood joined with animal glue are indicated in table 1 in such a way as to show whether the treated joints gave higher or lower test *results - with respect to strength in shear and percentage of wood failure - than joints glued without preliminary treatment under both good and starved-joint conditions.

The entire group of treated joints !-- 13 species --showed 51 percent greater average strength in shear than the untreated joints of the same species glued under starved-joint conditions, and 97 percent more wood f ailu re.

In the case of the caustic-treated black walnut listed in table 1, although the strength values were less than those for untreated wood, the improvement in the starved-joint condition is indicated by the increase in the percentage of wood failure. With black walnut the lower strength of the treated joints was apparently due to poorer quality wood.


Tests of Casein-glue Joints


The results of tests of caustic-treated casein-glue joints are presented in table 2. This table is similar to table 1 except that starved joints do not enter the comparison of treated and untreated joints.

Tests on caustic -treated casein-glue joints in osage.-orange gave striking results. Osage-orange contains a large amount of extractives and is one of the most difficult of all woods to join with casein glue. When this species was glued untreated, practically no adhesion at all occurred;, the joints showed an average strength in shear of only 294 pounds per square inch andnowood failure. When it was treatedwith caustic soda, however, the average joint strength was over 3, 000 pounds per square inch, and wood failure was 35 percent.

Lime water, ammonia, benzol, hydrochloric acid, and bleaching powder (chloride of lime) were other materials tested at the same time as the caustic soda. Hydrated lime (10 parts added to 90 parts of water) gave slightly better results than caustic soda when used as a surface treatment for hickory, red gum, and black cherry joined with casein glue. Of the other chemicals named above, some gave encouraging results on one or two species, but the results in general were not sufficiently consistent to warrant discussion in this note.







Table 1.- --Effect of caustic soda on animal-glue joints

(Wood treated with caustic soda and glued under
both good and starved-joint conditions)


Species of wood Average Average wood
strength : failure

:Lbs. per sq. in.: Percent

Basswood ............++ :+
Yellow birch......................... ++ .+
Black cherry.......................... ++ ++
Red gumn heart....................... ++ +
Red gurn sap......................... ++ .+
Sugar maple......................... ++. ++
Red oak............................. ++ *+
White oak........................... ++, ++
Osage -orange.......................... + :+
Northern white pine ...................++
Southern yellow pine ...................++ .+
Yellow poplar........................ ++. ++
Black walnut.............................. ++

+=More than value for untreated wood glued under starved-joint con
ditions.
++ =More than value for untreated wood glued under either sta rvc-za
joint conditions or good gluing conditions.
- = Less than value for untreated wood glued under either starved-joint
or good gluing conditions.




















-3-




UNIVERSITY OF FLORIDA


3 1262 09216 7914
Table Z. -Effect of caustic soda on casein-glue joints
(Wood treated with caustic soda and glued under
normal conditions)
Species of wood : Average :Average wood
strength f ailur e
- - -------------------------------------------------------------- --------------- ---------------:Lbs. per sq. in.-- Percent

Basswood ...................... + :+
Red gumheart........ .......: +
Bed gum sap .............. + *+
Hickory ........ .. ... .. ... ... + *+
Osage-orange. ... ... .. .. .. .. ... + *+
White oak. .. .. .. .. . .. .. .... :

R~edwood. .. .. .. . .. .. .. .. ... : + *+

!-Difference insignificant.

+ = More than value for untreated wood glued under same conditions.
- = Less than value for untreated wood glued under same conditions.
























Z M 304i10 F ...4. Agriculture-Madison