Styrene – ethylene – butylene – styrene elastomers (TPE-S) are a challenge for flame retardancy because they burn without residue and with a very high heat release (PHR > 2000 kW/m2).
Aluminium diethylphosphinate (AlPi) alone is effective in flame inhibition but does not achieve UL94-HB (3mm). However, when combined with other PIN FR compounds, a total 30% PIN FR loading enable to achieve this standard, that is almost immediate self-extinguishing in a horizontal set-up. Using AlPi as the principal component with melamine polyphosphate and either titanium dioxide or boehmite synergist, LOI of up to 27%, UL94-HB and a reduction in peak heat release of 85% to below 300 kW/m2 were achieved.
“Halogen-free fire retardant styrene–ethylene–butylene–styrene-based thermoplastic elastomers using synergistic aluminum diethylphosphinate–based combinations”, K. Langfeld A. Sut, et al., J Fire Sciences 2015, 33(2) 157-177 http://dx.doi.org/10.1177/0734904114565581