The analysis of response surface optimization and performance of cross-linked starch/tannic acid adhesive reinforced by phragmites fibers

The present study utilizes starch as the primary raw material for preparing a water-resistant biomass adhesive to replace formaldehyde-based resin adhesive, which is subsequently used in plywood production. The preparation process of starch-based adhesive (SBA) was optimized using response surface methodology (RSM), and the effects of the mass ratio of starch to tannic acid, the dosages of phragmites fiber and boric acid on wet-bond strength were studied. The quadratic regression model of SBA showed significant results (p < 0.0001). The optimal preparation condition was that the mass ratio between starch and tannic acid was 5:2, in the dosages of 2.9% for phragmites fibers and 3.2% for boric acid. The wet-bond strength of the plywood prepared with this adhesive was 1.73 MPa. Characterization analysis showed that the hydroxyl group on the surface of starch and tannic acid had complexation with boric acid, which improved the wet-bond strength, water resistance, and, thermal stability of the adhesive. The alkali-treated phragmites fibers had better compatibility with the starch matrix than the original fiber, which improved the cohesion of the SBA and increased the wet-bond strength by 26%. Highlights center dot The phragmites fibers have been used to reinforce starch-based adhesives. center dot Boric acid facilitates the formation of crosslinked structures. center dot The phenolic hydroxyl group in tannins provides excellent water resistance. center dot Phragmites fiber exhibits good compatibility with the adhesive matrix. center dot The cured starch-based adhesive has excellent wet -bond strength.