Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/10/2013
Publication Date: 1/1/2014
Citation: He, Z., Cheng, H.N., Chapital, D.C., Dowd, M.K. 2014. Sequential fractionation of cottonseed meal to improve its wood adhesive properties. Journal of the American Oil Chemists' Society. 91:151–158.
Interpretive Summary: Wood adhesives are needed for the manufacturing of wood composites. Interest in the use of natural protein-based adhesives for wood increased recently as these materials (natural proteins) are renewable, biodegradable, and more environmentally acceptable. A recent report demonstratd that cottonseed protein isolates performed as well as soy protein isolates as adhesives for wood composites. Cottonseed protein isolate, however, is prepared from flour by alkaline extraction followed by acid precipitation. The technique uses corrosive reagents and it makes protein isolate-based adhesives relatively expensive. To find an economic and more environment friendly way to formulate cottonseed proteins into wood adhesives, in this work, we tested the adhesive properties of various cottonseed flour fractions. Our data demonstrated that water- and buffer-washed cottonseed flour fractions were as good as cottonseed protein isolate when used as wood adhesive for the tested maple veneer. Some preparations and the isolates showed promising results regarding water resistance. However, additional work is needed to better define the applicability of these results.
Technical Abstract: To find a more environment-friendly and cost effective means to prepare cottonseed protein-based wood adhesives, cottonseed flours (i.e., defatted meals) were separated into several fractions. Flours from both glanded and glandless cotton varieties were used. The flour was extracted first with water then with a NaCl solution or with buffer (35 mM Na phosphate, pH 7.5) then with a NaCl solution. The recovered fractions were hot-pressed onto maple veneer strips and tested for their adhesive properties. The adhesive strength of the water- and buffer-washed fractions (i.e., the un-extractable residues) was increased compared with the adhesive strength of the original flour. The adhesive strength of these fractions was comparable to that of cottonseed protein isolate (>90% protein). Seed glanding did not appear to have a large effect on the adhesive performance of either the initial meals or their fractions. Additional extraction of the flour with a NaCl solution reduced adhesive performance. Resistance of the adhesives to water immersion was not as good for the flour or its fractions as it was for the protein isolate when the joints were glued at 80 °C but adhesive resistance was improved by raising the pressing temperature to 100 °C. The results suggest that water- or buffer-washed cottonseed flour fractions might be useful as wood adhesives and would be less costly to prepare than cottonseed protein isolates.