Posted on 29/11/2023 in Transport Fire Safety 2023
Phosphorus PIN FRs for safer bus interiors

Tests show phosphorus flame retardants reduce heat release and smoke compared to non-FR or halogenated FR ABS. Neat ABS polymer, a material widely used in bus and coach interiors, was compared to ABS with halogenated and with phosphorus PIN flame retardants (PFRs). 26 different ABS-PFR-synergist compounds were screened, and a compound with 10% AlPi (aluminium diethylphosphinate) and 10% APP (ammonium polyphosphate) was selected as optimal. This PFR-ABS showed <1/5 of peak heat release rate compared to neat ABS (around 1/3 if ABS-halogen-FR) and somewhat lower total smoke production and lower maximum smoke density compared to neat ABS (whereas halogenated FR ABS showed nearly double total smoke production). Further, six commercial bus interior materials meeting the existing bus and coach fire safety regulation UNECE R118 were tested (FR-ABS, and FR-ABS + polycarbonate). These showed high smoke release, smoke gas toxicity, and risk of melting-burning spread of fire. In some cases, presence of halogen FRs led to significant HCl or HBr toxic gas release. The authors conclude that current bus material fire safety regulations are inadequate and do not address smoke and fire gas toxicity.

“Fire safe bus interior materials – flame retardants and the effect on smoke production and smoke gas toxicity”, A. Sandinge et al., in Proceedings from the Seventh International Conference on Fires in Vehicles, Stavanger, Norway, April 24-25, 2023, RiSE

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