Analysis of soy flour/phenol-formaldehyde adhesives for bonding wood

The desire to make more environmentally friendly and lower-cost bonded wood products has led to an interest in replacing some phenol and formaldehyde in wood adhesives with soybean flour. It is important to develop tests that relate resin production variables to resin properties before and after wood bonding. The protein needs to be denatured, with minimal hydrolysis, to maximize its in-corporation into the final polymerized structure. In this study, the best conditions for denaturing were found to be maintaining the temperature below 100°C and reacting the soy flour with sodium hydroxide for about 1 hour. Gel permeation chromatography was optimized to determine conditions for selectively breaking down the high molecular weight protein fragments that contribute to high adhesive viscosity. This method and extraction data were used to evaluate the reaction of the denatured soy flour protein with formaldehyde and phenol. Results were used to develop more environmentally friendly face adhesives for oriented strandboard.