Cross-linked soy-based wood adhesives for plywood

To improve the water resistance of soy-based adhesive for wood panels, three kinds of cross-linkers, namely, epoxy resin (EPR), melamine–formaldehyde (MF) and their mixture EPR+MF were used in this paper. The results indicated that all the three cross-linkers improved the water resistance of soy-based adhesive and the hybrid cross-linker EPR+MF, was the best. With press temperature 160 °C and press time 8 min, type II and even type I plywood could be prepared when 6.4%EPR+6.4%MF is used as cross-linker of soy-based adhesive. FT-IR indicated that the great improvement of water resistance of soy-based adhesive modified with EPR and MF might be caused by the reaction between epoxy and –OH, and that between MF and –NH.