Facile modification of aluminum hypophosphate and its flame retardancy for polystyrene

Abstract

A phosphorus-containing flame retardant, aluminum hypophosphite (AHPi), has been modified by (3-aminopropyl) triethoxysilane (KH550) to prepare flame-retardant polystyrene (PS). The influence of modified AHPi on the morphology and characterization was investigated, and differences in flame retardant properties of the PS/AHPi and PS/modified AHPi were compared. The PS composite can pass the vertical burning tests (UL-94 standard) with a V-0 rating when the mass content of modified AHPi reaches 20%, compared with the mass content of 25% AHPi. The element mapping of the PS composite shows that modified AHPi has better dispersion in PS than AHPi. Thermogravimetric analysis results indicated that adding modified AHPi can advance the initial decomposition temperature of the composite material. With the addition of modified AHPi, the decrease in peak heat release rate (pHRR) is more evident than AHPi, and the char yield of the resultant PS composites gradually increased. With the addition of 25% modified AHPi, the pHRR and total heat release of PS composites decreased by 81.4% and 37.6%. The modification of AHPi promoted its dispersion in the PS matrix and improved the char formation of PS composites. The results of real-time infrared spectrometry of PS composites, Fourier transform infrared spectra and X-ray photoelectron analysis of the char layer indicated that modified AHPi has flame retardancy in condensed and gas phases.