Thermal Degradation Kinetics of a Intumescent Flame Retardant System for Halogen-Free Flame Retarded EVA

An intumescent flame retardant (IFR) system containing phosphorus-silicon (EMPZR) and ammonium polyphosphate (APP) was used to improve the flame retardancy of poly(ethylene-co-vinyl acetate)(EVA). The influence of EMPZR contents on the flame retardance of EVA/EMPZR/APP composites has been studied. It was found that the reasonable mass ratio of EMPZR/APP in EVA/EMPZR/APP composites is 20/20, whose limiting oxygen index (LOI) value was improved from 19.0 for EVA to 28.6, and the burning grading reached to UL-94 V-0. The thermal behavior of EVA and IFR-EVA was investigated by dynamic thermo gravimetric analysis (TGA) at different heating rates and then the thermal degradation activation energies of EVA and IFR-EVA were determined by using Flynn-Wall-Ozawa method. Meanwhile, morphology of the char residue obtained from burning IFR-EVA in LOT test was studied through the scanning electron microscopy SEM observation, the rich compact char layer in which could explain the good flame retardance and the synergistic effect between EMPZR and APP.