Soy protein adhesives improved by SiO2 nanoparticles for plywoods

摘要

Purpose - Soy protein has been considered as a renewable and environmentally friendly source of adhesives. The purpose of this paper is to investigate a new approach for making a soy protein adhesive modified by SiO2 nanoparticles. Design/methodology/approach - The objective of this investigation was to evaluate the adhesive properties by determining the viscosity, wettability and shear strength of soy protein adhesive. The effects of nano-SiO2 content, wood surface roughness and processing pressure on shear strength between soy protein adhesive and wood were investigated. Four nano-SiO2 contents (0, 0.5, 1 and 2 percent), two wood surface roughness (40 and 280 grits), and two processing pressure (1 and 2 MPa) were tested. Adhesive performance was evaluated based on the maximum force required for shearing the adhesive bond between cherry wood pieces. Findings - The modified soy protein adhesives by SiO2 nanoparticles showed a significant enhancement in dry strength with nano-SiO2 content of 1 percent. The mechanism appears to be related to the increased interaction between adhesive and wood and the elimination of voids on the wood surface by SiO2 nanoparticles. Research limitations/implications - The adhesive resins used in the present context was soy protein isolate, not from commercially available soy flour. The wet strength was not satisfactory. Further study is needed to solve this problem. Practical implications - The method developed provided a simple and practical solution to improving the shear strength of soy protein adhesives. Originality/value - The enhancement method for adhesion strength of soy protein was novel and could find numerous applications in wood industry, avoiding formaldehyde emission and reducing the dependence on petroleum products.