An environment-friendly wood adhesive using modified wheat gluten by isophorone diisocyanate

Abstract A highly efficient method was developed for preparing wheat gluten (WG) based wood adhesives with high performance using ethanol and isophorone diisocyanate (IPDI) as main chemical additives. The performance of the resulting adhesives was evaluated by manufacturing artificial wood products (AWP). The effects of IPDI content on the water resistance, viscosity, solid content and modification mechanism of the adhesives and the optimal method to prepare artificial wood products were investigated. The results showed that ethanol could disperse the stacked protein structures and expose some internal groups of proteins, so that IPDI could be cross-linked with protein molecules to form a more compact three-dimensional reticulum protein structure, confirmed by both the increases of the decomposition temperature and the smoother and more uniform surface of the resulting adhesives. The structural changes enhanced the hydrophobicity of the modified adhesive samples and were beneficial to resist the invasion of water molecules, which improved the water resistance of the adhesives. When the IPDI concentration was 15 wt%, the dry and wet shear strength of the adhesive reached 2.61 MPa and 0.97 MPa with the best water resistance respectively, and the viscosity and solid content increased to 32.8 Pa·s and 34.41 %, respectively. It was found that the resulting adhesives had better performance and could be used as an environment-friendly plywood adhesive instead of petroleum-based adhesive, which was more conducive to the extension of the wheat industry chain to high value-added products.