A formaldehyde-free, high-performance soy protein-based adhesive enhanced by hyperbranched sulfuretted polyamidoamine-epichlorohydrin resin.

A self-synthesized hyperbranched sulfuretted polyamidoamine-epichlorohydrin (PCDME) resin was developed to enhance high-temperature soybean meal (HSM) protein-based adhesives. In PCDME-modified HSM adhesives, a multi-crosslinked network is built based on ring-opening reactions, disulfide bond rearrangement, electrostatic interactions, and hydrogen bonding between the active groups in PCDME resins and HSM proteins. This results in the HSM-based adhesive with significantly enhanced internal cohesion, thermal stability, moisture resistance and bonding strength. HSM/PCDME-25 % had excellent dry and wet bond strengths of 2.23 MPa and 1.52 MPa, increasing by 46 % and 322 %, respectively, over the control and increasing toughness (work of adhesion) by 150 %. This PCDME-modified protein-based adhesives also have a satisfactory solid content and a good adhesion of various substrates.