A Novel Bio-Based Zirconium Phosphonate as a Flame Retardant and Smoke Suppressant for Epoxy Resin

Although epoxy resin has been widely used in various fields, it still suffers from some problems including brittleness and flammability. In this study, a new phosphonic acid, N, N-bis(phosphomethyl) glycine (GDMP), was prepared by Mannich reaction with bio-based glycine and then a novel layered zirconium phosphonate (ZrGDMP) was synthesized using GDMP and zirconyl chloride hydrate as reactants. The chemical structure of ZrGDMP was well characterized by H-1 and P-31 NMR, SEM, XRD and XPS. The effect of ZrGDMP on the flame retardancy, smoke suppression, strengthening and toughening performances of the epoxy matrix was investigated and evaluated. TGA results indicated that compared with pure EP, ZrGDMP-EP composites showed higher char yield due to the catalytic charring effect of ZrGDMP. The pure EP exhibited high flammability, while ZrGDMP-EP composites possessed excellent thermal stability and remarkable fire resistance. The PHRR, THR, and TSP values of 3wt% ZrGDMP-EP were obviously declined by 39.6%, 40.2%, and 24.9% compared to these of pure EP. Moreover, the tensile and impact tests implied that the addition of ZrGDMP can significantly reinforce the toughness as well as the strength of EP in terms of higher impact strength (24.8 kJ/m(2)) and tensile strength (57.7 MPa), which was mainly contributed to the uniform dispersion of ZrGDMP within the EP matrix.