Combinations of soy protein and polyacrylate emulsions as wood adhesives

A series of soy protein-polyacrylate emulsions (SPCE) used for wood adhesives were synthesized by blending soy protein in aqueous solution and polyacrylate emulsion with various mass fractions. The chemical composition and performance properties of these blends were then characterized by FT-IR viscometry, contact angle analysis, scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and shear strength. It was found that the apparent viscosity of these blended emulsions decreased with higher levels of polyacrylate emulsion, which could facilitate the wetting and penetrating of wood. FT-IR analysis suggested that hydrogen bonds were formed in the blends. The introduction of polyacrylate copolymers containing neutralized poly(acrylic acid), as well as a small amount of emulsifiers, can enhance the wettability of blended emulsions and facilitate their application as wood adhesives. The shear strength of plywood prepared using these adhesives and their thermal stability were improved after the introduction of the polyacrylate copolymers.