Experimental and Numerical Study of Thermal Stability and Fire Performance of Brominated and Halogen-free Flame Retardants in Glass-fibre Reinforced Poly(butylene terephthalate)

This paper investigates the effects of brominated and halogen-free fire retardants on the thermal stability and fire performance of glass-fibre reinforced poly(butylene terephthalate). Brominated polystyrene was used as the brominated fire retardant (BFR), whereas aluminium diethylphosphinate (Alpi) with/without nanoclay as halogen-free fire retardants (HFFRs). Tests were conducted using thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL94 and the cone calorimeter. TGA results show that decomposition of glass-fibre plus PBT (PBT+GF) starts earlier in the presence of fire retardants (FRs). In the cone calorimeter, all FRs reduce significantly the heat release rate (HRR) compared to PBT+GF, with brominated polystyrene achieving lower HRR primarily because bromine released in the pyrolysis gases inhibits combustion, without however changing the mass loss rate (MLR). Alpi alone has significant effects on reduction of both HRR and MLR, which become considerably more when combined with nanoclay. The efficiency of combustion of the brominated polystyrene compound is much lower than that of HFFRs, which indicates that unburned pyrolysing gases are released during the combustion of brominated fire retardants.