Fabrication of soybean protein-acrylate composite mini-emulsion toward wood adhesive

A series of soybean protein-acrylate composite mini-emulsions used for wood adhesive were facilely synthesized by mini-emulsion polymerization. The chemical compositions, properties and adhesive performances of composites were characterized by FTIR, SEM, TEM, TGA, DSC, XPS and bonding strength. The results indicated the copolymerized emulsions had appropriate particle sizes and uniform particle distribution. Soy protein could make active groups crosslinked with polyacrylate within or between molecules. The glass transition temperature (Tg) of acrylate was changed after adding soy protein. The binding energy of C (1 s) had a significant change. Besides, parts of C-O and C=O groups reacted to soybean protein and finally formed carboxyl groups. Bonding strengths of plywood prepared by mini-emulsion were all higher than 0.7 MPa, meeting the standard of GB/T9846-2004 II. The successful fabrication of soyprotein acrylate composite adhesives could open up a new way for wood adhesives with no release of free phenol nor free formaldehyde.