Wood adhesive properties of cottonseed protein with denaturant additives

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

Submitted to: Journal of Adhesion Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2017
Publication Date: 9/25/2017
Citation: Cheng, H.N., Ford, C., Dowd, M.K., He, Z. 2017. Wood adhesive properties of cottonseed protein with denaturant additives. Journal of Adhesion Science and Technology. 31(24):2657–2666.

Interpretive Summary: Currently cotton fiber accounts for about 90% of cotton's total economic value, but there are many cotton byproducts available, which can also be utilized to benefit cotton growers and processors. One of the promising cotton byproducts is cottonseed protein, and we have been evaluating it as a raw material for wood adhesives. In order to make cottonseed protein competitive relative to other adhesive types, we need to improve its benefit/cost ratio. One approach is to find additives that can enhance the protein’s adhesive performance. In this work, we studied a number of denaturants as additives and optimized the protein concentration, pH, and the additives' dosage levels. The cottonseed protein was found to perform well with denaturant reagents such as guanidine hydrochloride, sodium dodecyl sulfonate, and urea, and the protein/denaturant combinations enhanced the dry adhesive strength of cottonseed protein by 25-47% at optimal additive concentrations. Furthermore, at least 60% of the adhesive strength was retained after hot water treatment for many of the formulations, indicating substantial hot water resistance. The information obtained in this work will be useful in increasing our basic knowledge of cottonseed protein-based adhesives and also providing us the option of developing improved adhesive formulations using cottonseed protein/denaturant combinations.

Technical Abstract: Most commercial wood adhesive use either formaldehyde-based resins or polyurethanes, both of which include potentially toxic chemicals in their formulations. As a result, proteins are being considered as greener and more sustainable wood adhesives. While most of the protein adhesive studies focus on soy proteins, there is also interest in exploring alternatives. In this work, testing of the adhesive performance of cottonseed protein isolate was undertaken in the presence of protein denaturants, i.e., guanidine hydrochloride (GuHCl), sodium dodecyl sulfonate (SDS), urea, and alkali. For comparison, soy protein isolate was also included in the study. At optimal dosage levels, the dry adhesive strength of cottonseed protein isolate could be enhanced by 38, 25, or 47% with SDS, GuHCl, or urea, respectively. The dry adhesive strength and hot water resistance of cottonseed protein isolate was generally superior to that of soy protein isolate, with or without the denaturants. Thus, the combination of cottonseed protein with an optimal concentration of a denaturant may be a potentially promising polymeric system for use as wood adhesives.