On the performance and mechanism of brominated and halogen free flame retardants in formulations of glass fibre reinforced poly(butylene terephthalate)

The performance and mechanism of brominated and halogen free flame retardants in formulations of glass fibre reinforced poly(butylene terephthalate) composites were investigated. This study entailed four glass fibre reinforced PBT formulations, namely, (i) glass fibre reinforced PBT without flame retardant, (ii) glass fibre reinforced PBT combined with one brominated flame retardant (10 wt% of brominated polystyrene), (iii) glass fibre reinforced PBT combined with one halogen free flame retardant (15 wt% of aluminium diethyl phosphinate), and (iv) glass fibre reinforced PBT combined with two halogen free flame retardants (15.5 wt% of aluminium diethyl phosphinate and 2.5 wt% of natural montmorillonite clay modified with methyl, octadecyl, bis-2-hydroxyethyl quaternary ammonium salt). Their fire performance is compared using LOI, UL-94, thermogravimetric analysis (TGA), differential thermogravimetry (DTG), evolved Fourier transform infrared gas analysis (TGA-FTIR), Fourier transform infrared solid residue analysis (FTIR-ATR), and cone calorimetric studies. The results of this study show that aluminium diethyl phosphinate combined with natural montmorillonite clay, chemically modified with a quaternary ammonium salt, provides an alternative to brominated flame retardants in glass fibre reinforced PBT composites.