Study on the Preparation Process Optimization of Plywood Based on a Full Biomass Tannin-Sucrose Wood Adhesive

Abstract

Biomass adhesive is conducive to decreasing the dependence of the wood adhesive industry on synthetic resin based on fossil resources and improving the market competitiveness of adhesives. It is also a critical breakthrough to realize the goal of carbon peaking and carbon neutrality in the wood industry. In this study, a full biomass wood adhesive composed of tannin and sucrose was developed and applied successfully to the preparation of ply-wood. The preparation technique of plywood was optimized, and the chemical structure, curing performance, crystallization property and thermal performance of the adhesive were investigated. Results showed that: (1) hot-pressing temperature played a decisive role in the performances of tannin-sucrose composite adhesives and it also had a very significant influence on the water resistance of plywood. (2) The preparation of tannin-sucrose composite adhesive was a process in which sucrose was transformed into furan aldehydes and then made cross-linking reaction with tannin. These composite adhesives could only get good bonding performances when the curing temperature was above 210°C. (3) The optimal plywood preparation technique was: hot-pressing temperature of 220°C, hot-pressing time of 1.2 min/mm, m(tannin):m(sucrose) of 60:40, and adhesive loading of 160 g/m2. The wet bonding strength in boiling water of the prepared plywood was 0.83 MPa, meeting the strength requirements of Type-I plywood in the standard of GB/T 17657-2013. (4) The curing temperature of tannin-sucrose composite adhesive was further decreased by lowering the temperature during the transformation of sucrose into 5-HMF, which was a key in subsequent research.