Effect of rare earth hypophosphite and melamine cyanurate on fire performance of glass-fiber reinforced poly(1,4-butylene terephthalate) composites

This work mainly deals with a novel flame retardant system for glass-fiber reinforced poly(1,4-butylene terephthalate) (GRPBT) composites using trivalent rare earth hypophosphite (REHP) and melamine cyanurate (MC) through melt blending method. Firstly, two types of REHP, lanthanum hypophosphite and cerium hypophosphite, were synthesized and characterized. Thermal gravimetric analysis (TGA) was employed to investigate the thermal decomposition behavior of REHP and flame retardant treated GRPBT composites. Thermal combustion properties were measured using microscale combustion calorimeter. Fire performance was evaluated by limiting oxygen index, Underwriters Laboratories 94 and cone calorimeter. The results showed that the flammability of GRPBT is significantly reduced by the incorporation of the flame retardant mixture. Mechanism analysis revealed that the addition of MC reduces the condensed phase effect of REHP, but improves the flame inhibition in gas phase.