Blending cottonseed meal products with different protein contents for cost-effective wood adhesive performances

Water washed cottonseed meal (WCSM) is an excellent bio-adhesive resource because of its cost-effective extraction process and environmentally friendly performance. To evaluate the effects of protein content on the adhesive performance of cottonseed meal-based adhesives, we reconstituted cottonseed meal products with protein contents ranged from 34.9% to 94.8% by blending different amounts of WCSM, cottonseed protein isolate (CSPI), and residues after protein extraction (CSIR). Their physicochemical properties and three types of adhesive strengths (dry, wet, and soaked) were measured with press temperatures at 100, 150 and 170 degrees C. The morphological and rheological data showed that the low-protein-content adhesives with a high amount of residual cotton hull and fiber possessed poor spreadability and adhesive strength. Molecular and thermal analysis suggested that protein ratio had a stronger influence than press temperature to thermal property and adhesive strength. With these data, multiple linear regression models were established, providing analytical tools to predict the bonding strength affected by protein content and press temperature in cottonseed meal-based adhesives. On the other hand, the blends with 65-70% of protein content demonstrated the bonding performance and flowability comparable to highest protein product CSPI (94.8% protein) within the acceptable standard deviations. Thus, these observations and data could be helpful in set-up of industrial standard requirements and quality control for protein content in cost-effective adhesive-grade WCSM products.