Novel Materials from Agroproteins: Adhesives from Modified Soy Protein Polymers

Soy protein polymers recently have been considered as alternatives to petroleum polymers to ease environmental pollution. The use of soy proteins as adhesives for plywood has been limited because of their low water resistance. The objective of this research was to enhance the water resistance of adhesives made from urea modified soy proteins. Alkali-modified and heat-treated soy proteins were used for comparison. Two ASTM standard methods for gluing strength and water resistance of wood were tested. The urea-modified soy proteins had stronger gluing strength for plywood than the nonmodified soy proteins. Urea-modified proteins had higher water resistance than alkali-modified and heat-treated proteins. After three cycles of 48 hours of water soaking followed by 48 hours of drying, 0% delamination was found for both walnut and pine specimens glued with the urea-modified soy protein adhesives.