Use of additives to enhance the properties of cottonseed protein as wood adhesives

Authors: Cheng, Huai; Ford, Catrina; Dowd, Michael; He, Zhongqi

Submitted to: International Journal of Adhesion and Adhesives
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2016
Publication Date: 3/4/2016
Citation: Cheng, H.N., Ford, C., Dowd, M.K., He, Z. 2016. Use of additives to enhance the properties of cottonseed protein as wood adhesives. International Journal of Adhesion and Adhesives. 68:156-160.

Interpretive Summary: An ongoing trend in wood adhesives is to use proteins instead of formaldehyde resins and urethanes as eco-friendly adhesive ingredients. In comparison to soy protein, cottonseed protein has not been widely used in wood adhesive formulations. The purpose of this work is first to demonstrate that cottonseed protein isolate provides higher adhesive strength and hot water resistance relative to soy protein isolate on pine, walnut, cherry, and maple wood veneers. The second purpose is to show that specific additives, such as small molecules containing carboxylic acids (e.g., aspartic, glutamic, acetic, butyric, and adipic acid) can impart enhanced adhesive performance to cottonseed protein isolate without hurting its hot water resistance. In contrast, these same additives do not significantly enhance the adhesive strength of soy protein but even reduce the hot water resistance of soy protein. Thus, the combination of cottonseed protein and one of these modifiers has a significant performance advantage over soy protein in wood adhesive formulations.

Technical Abstract: Soy protein is currently being used commercially as a “green” wood adhesive. Previous work in this laboratory has shown that cottonseed protein isolate, tested on maple wood veneer, produced higher adhesive strength and hot water resistance relative to soy protein. In the present study, cottonseed protein and soy protein isolates were tested on different wood types, and cottonseed protein again showed better performance relative to soy protein. Furthermore, the effects of several protein modifiers were evaluated, including amino acids, fatty acids, and other organic molecules with cationic or anionic charges. Aspartic acid, glutamic acid, acetic acid, butyric acid, and adipic acid gave improved performance when included with cottonseed protein isolate whereas no significant effect was observed on soy protein isolate. Both dry adhesive strength and hot water resistance were tested. The enhanced performance observed with these additives provides an additional incentive for the use of cottonseed protein in this application.