Preparation of glycidyl methacrylate grafted starch adhesive to apply in high-performance and environment-friendly plywood

In this paper, cassava starch was used as the main raw material to prepare high performance and environment-friendly starch-based adhesive. Starch was grafted with glycidyl methacrylate (GMA), and then cross-linked with sodium trimetaphosphate (STMP). Before preparation of plywood, polyaryl polymethylene isocyanate (PAPI) was mixed as chain extension agent. Prepared starch adhesives are used in wood-based panel applications. From the Fourier transform infrared (FTIR) analysis, it was found that GMA was successfully grafted to the starch adhesives which improved the hydrophobicity and shear strength of the adhesive. The plywood using modified starch adhesive at pH 4.50-5.50 showed the highest wet shear strength, 1.00 MPa, which was 163% higher than that using unmodified starch adhesive. The Scanning electron microscopy (SEM) results showed that the original morphology of starch particles were destroyed and became smaller during GMA grafting, which made the modified starch-based adhesive easier to penetrate into the bonding interface of plywood. The characterization results of the adhesive film also showed that the mechanical properties of the adhesive were better when the grafting reaction pH was 4.50-5.50. Graft copolymerization modification of starch improves the hydrophobic properties of starch binders.