A novel environmentally friendly hot-pressed peanut meal protein adhesive

The plant protein-based adhesives are a promising alternative to petroleum-based adhesives, while the low bonding strength, water resistance and mildew-proofing limit their application in plywood industry. In this study, hot-pressed peanut meal protein (HPMP) adhesive with enhanced bonding strength was successfully prepared using a three-step method of sodium dodecyl sulfate (SDS) denaturation, nano-silica (nSiO2) reinforcement and polyamide polyamine epichlorohydrin resin (PAE) crosslinking. The boiling water strength of HPMP adhesive (0.85 MPa) exceeded the bonding strength requirement of China National Standards class Ⅰ plywood (0.7 MPa), and the mildew resistance of HPMP adhesive was extended at least 12 days. Simultaneously, the solids content and viscosity of HPMP adhesive increased by 45.4% and 274.6% respectively. The bonding strength-enhancing mechanism of HPMP adhesive was further clarified by using HPM protein isolate (HPMPI) adhesive. That is, the ring network structures were formed by connecting with hydrogen bonds, ester bonds and ether bonds, and clearly observed by double spherical aberration-corrected scanning transmission electron microscopy. Thus, the prepared novel HPMP adhesive has great potential for application as an environmental-friendly commercial wood adhesive for plywood production.