High bonding strength and boiling water resistance of soy protein-based adhesives via organosilicon-acrylate microemulsion and epoxy synergistic interfacial enhancement

Boiling water resistance, an important indicator of wood adhesives, represents the capability of adhesives for exterior woodwork applications. However, soy-based adhesives show poor behaviors in this respect, which limit their applications in outdoor environments. In this article, we report a synergistic modification method of integrating a cocrosslinking system of epoxied polyamideamine-epichlorohydrin (PAE) and organosilicon-acrylate copolymer latexes (OACLs) to improve soybean meal (SM)-based adhesive properties. Tailored PAE and OACL SM-based adhesives demonstrated robust crosslinking structures via multi-interfacial interactions, where PAE and OACL served as building blocks of an interpenetrating network, which was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The dry-shear strength, wet-shear strength, and boiling water strength of the resulting SM-based adhesives were 1.41 +/- 0.13, 1.32 +/- 0.17, and 1.20 +/- 0.11 MPa, respectively, with 15 wt % OACL loading; these were 41, 45, and 90% increases, respectively, over the SM-PAE adhesive with which we compared them. Most importantly, the excellent boiling water resistance of the adhesives make them practical for exterior plywood. (c) 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46061.