Halogen-Free Multicomponent Flame Retardant Thermoplastic Styrene-Ethylene-Butylene-Styrene Elastomers Based on Ammonium Polyphosphate-Expandable Graphite Synergy

Developing flame retatded thermoplastic elastomers (TPES) based on styrene-ethylene-butylene-styrene, polypropylene, and mineral oil is a challenging task because of their very high fire loads and flammability. A promising approach is the synergistic combination of expandable graphite (EG) and ammonium polyphosphate (APP). Cone calorimetry, oxygen index, and UL 94 classification were applied. The optimal EG:APP ratio is 3:1, due to the most effective fire residue morphology. Exchanging APP with melamine-coated APPm yielded crucial improvement in fire properties, whereas replacing EG/APP with melamine polyphosphate,did not. Adjuvants, such as aluminum diethyl phosphinate zinc borate, melamine cyanurate, titanium dioxide, dipentaerylthritol, diphenyl-2-ethyl phosphate, boehmite, SiO2, chalk, and talcum, were tested. All flame retardants reinforced the TPE-S. The combination with AIPi is proposed, because with 30 wt % flame retardants a maximum averaged rate of heat emission below 200 kW m(-2) and a V-0 rating was achieved. Multicomponent EG/APP/adjuvants systems are proposed as a suitable route to achieve efficient halogen-free flame retarded TPE-S.