Effects of melamine cyanurate and aluminum hypophosphite on the flame retardancy of high-impact polystyrene

A novel composite based on melamine cyanurate (MC) and aluminum hypophosphite (ALHP) was successfully incorporated into high-impact polystyrene (HIPS). The flame retardancy and combustion properties of the composite were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis as well as by vertical combustion, limiting oxygen index (LOI), and cone calorimetry tests. When the ratio of MC to ALHP was 1:4 (comprising a total of 20 wt.% of the mass of HIPS), the resulting composite (HIPS-5) reached a UL-94 V-0 classification, and the LOI increased from 19.3 to 26.7%. Relative to pure HIPS, the peak heat release rate of HIPS-5 decreased from 807.64 to 180.71 kw m–2, and the total heat release decreased from 93.20 to 60.43 MJ m–2. In addition, the carbon residue of HIPS-5 increased from 6.83 to 21.14%, which was higher than all of the other samples. SEM analysis of the carbon residue after combustion in the cone calorimeter showed that a dense and stable carbon layer was formed on the surface of the HIPS composites. These data indicated that MC and ALHP demonstrated an apparent synergistic role as a flame-retardant system to protect HIPS from further combustion.