Flame retardancy mechanisms of aluminium phosphinate in combination with melamine cyanurate in glass-fibre-reinforced poly(1,4-butylene terephthalate)

The flame retardancy mechanisms of aluminium diethylphosphinate (AlPi) and its combination with melamine cyanurate (MC) in glass-fibre-reinforced poly(butylene terephthalate) (PBT/GF) were analysed using TGA including evolved gas analysis (TGA-FTIR), cone calorimeter measurements using various irradiations, measurements using various irradiations, flammability tests (limited oxygen index, LOI, UL 94) and chemical analyses of residues (FTIR, SEM/EDX). AM decomposed mainly through the formation of diethylphosphinic acid and aluminium phosphate and influenced the decomposition of the PBT only slightly. AlPi acted mainly through flame inhibition. A halogen-free V-0 PBT/GF material was achieved with a LOI of 44%. Additional charring influenced the flammability. MC decomposed independently of the polymer and showed some fuel dilution effects.