Protein-based glyoxal–polyethyleneimine-crosslinked adhesives for wood bonding

Corn gluten protein, potato protein, and pea protein isolate were used as natural raw materials for preparing bio-based environmentally friendly adhesives. Glyoxal and polyethyleneimine (PEI) were used as crosslinking agents. Dry and wet bonding performances of the adhered wood samples were tested for different protein-based adhesives, i.e., protein alkaline-modified adhesives, protein–glyoxal adhesives, and protein–glyoxal–PEI adhesives. The results indicate that crosslinking by glyoxal and polyethyleneimine effectively improves the bonding performance of pea, corn, and potato protein-based adhesives after water storage.