Synergistic effects of synthetic phosphonium sulfonates with expandable graphite on flame retardancy for EVA rubber blends

Synergistic effects of synthetic phosphonium sulfonates (PhSs) bearing different groups with expandable graphite (EG) on flame retardancy properties in poly(ethylene-co-vinyl acetate) (EVA) rubber blends have been studied by limiting oxygen index (LOI), UL-94 test, cone calorimeter test (CCT), and thermogravimetric analysis (TGA). The EVA/EG/PhS composites revealed excellent flame retardancies. Upon adding 2.5 wt% of PhSs and 20 wt% of EG to EVA matrix, V-0 rating can be achieved. The heat release rate (HRR) and the total heat release (THR) of EVA/PhS-2(2.5 wt%)/EG(20 wt%) and EVA/PhS-4(2.5 wt%)/EG(20 wt%) blends decreased remarkably based on CCT. In addition, the thermal stabilities and mechanical properties of EVA/EG/PhS composites did not deteriorate comparing with those of EVA/EG composites.