A simple method is developed for characterizing the fire performance and toxicity of polymers using basically three but up to five parameters if necessary. The first parameter is related to fire spread and growth (corresponding to UL-94 and the FIGRA of SBI), the second parameter is the smoke yield (corresponding to the SMOGRA of SBI), the third parameter is the inefficiency of combustion (related to unburned hydrocarbon compounds and their toxicity as verified by tube furnace measurements), the fourth parameter is the mass of residue remaining and the fifth parameter is a heat release parameter for thermally thin conditions (the maximum mass loss rate in TGA multiplied by the effective heat of combustion deduced from the Cone Calorimeter tests). The developed methodology was used to compare brominated and halogen free fire retardants in formulations of PBT, PA66, PPE/HIPS and PC/ABS. It is confirmed that the studied environmentally friendly alternatives to brominated fire retardants offer comparable fire performance with lower toxicity.

SummaryThis paper investigates the effects of brominated and halogen-free fire retardants on the fire performance of glass-fiber (GF) reinforced poly(butylene terephthalate) (PBT). Brominated polystyrene was used as the brominated fire retardant, whereas aluminum diethylphosphinate with/ without nanoclay as halogen-free fire retardants (HFFRs). Tests were conducted by using thermogravimetric analysis, limiting oxygen index (LOI), UL94, and the cone calorimeter. Thermogravimetric analysis results show that decomposition of GF plus PBT (PBT + GF) starts earlier in the presence of all fire retardants (FRs). In the cone calorimeter, all FRs reduce significantly the heat release rate (HRR) compared with PBT + GF, with brominated polystyrene achieving lowest HRR primarily because bromine released in the pyrolysis gases inhibits combustion. Brominate polystyrene does not, however, affect the mass loss rate. Aluminum diethylphosphinate alone has significant effects on reduction of both HRR and mass loss rate, which become considerably more when combined with nanoclay. It was also found that the combustion efficiency of the brominated polystyrene compound is much lower than that of HFFRs, indicating that brominated polystyrene has higher gas phase flame retardant efficiency compared with HFFRs because the bromine radicals released during degradation of brominated polystyrene effectively quench the chemical reactions of the pyrolysis gases due to degradation of PBT. KEYWORDS brominated fire retardants, cone calorimeter, halogen-free fire retardants, LOI, thermogravimetric analysis, UL94

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