Preparation and investigation of an eco-friendly plywood adhesive composed of sucrose and ammonium polyphosphate

In this study, sucrose and ammonium polyphosphate (APP) were utilized as the raw materials to prepare an environmentally-friendly plywood adhesive. The bonding performance results showed that the optimal synthesis conditions of the sucrose-ammonium polyphosphate (SAPP) adhesive were an 80/20 mass ratio (sucrose/APP) at 115 oC for 3 h, and the optimal manufacturing conditions were 170 oC for 7 min. In addition, the maximum wet shear strength of the obtained three-ply plywood was 0.81 MPa, which satisfied the China National Standard GB/T 9846–2015 (wet shear strength≥0.7 MPa). The insoluble mass proportion was positively associated with the heating temperature and time. The TG and DSC analysis showed that a rapid mass loss of the SAPP adhesive occurred at 143.4 oC, and endothermic peaks appeared at 136.2 and 156.4 oC. The 13C NMR spectra showed that the adhesive contained monosaccharides, oligosaccharides, ketones, HMF, Schiff bases, and various other unknown substances. This implies that hydrolysis, caramelization, and the Amadori rearrangement occurred during synthesis. Furthermore, the FT-IR and Py-GC/MS results indicated that the cured SAPP adhesive was a complex polymer containing furan and nitrogenous compounds, which were connected by dimethylene ether bridges.