Effect of polypropylene on the pyrolysis of flame retarded high impact polystyrene

Pyrolysis of high impact polystyrene (HIPS), containing decabromodiphenyl oxide as brominated flame retardant (BFR) with Sb2O3 as a synergist (Br–Sb–HIPS), often leads to high concentrations of toxic brominated organic compounds in the pyrolysis oils which would detrimentally impact the reuse of these pyrolysis oils. In this work, the pyrolysis of Br–Sb–HIPS in the presence of polypropylene (PP) at different blending mass ratios using a fixed bed reactor at 410°C was performed to investigate what the effect of PP has on the pyrolysis of Br–Sb–HIPS. The thermal decomposition characterization of Br–Sb–HIPS and PP was investigated using thermogravimetry analysis (TGA). The pyrolysis oils were analyzed using Fourier transform infrared spectroscopy (FTIR) and gas chromatography–mass spectrometry (GC–MS). TGA revealed that there was a synergistic interaction between Br–Sb–HIPS and PP during co-pyrolysis process. More wax/oil and less gas were produced and the yields of toluene, ethylbenzene, styrene and many other compounds in the pyrolysis oil reversely increased in the presence of PP. Moreover, PP was found to be effective to reduce bromine in the pyrolysis oil. When 30wt.% PP was blended into Br–Sb–HIPS, it could reduce the amount of bromine in pyrolysis oil to 38% of the original value. This graph shows the effect of PP on debromination (red solid, experimental; blue dash, expected; black solid, debromination rate). It was found that the content of bromine in the pyrolysis oil decreased as PP increases and the most important point was that the trend was below the expected trend without considering the effect of PP. [Display omitted] •Provided an efficient approach for recycling the WEEE plastics•Improved the recycle efficiency of HIPS plastics by mixing with polyolefins•Interpreted the decomposition characteristics of the co-pyrolysis of Br–Sb–HIPS and PP•Proposed a useful method for debromination in the pyrolysis oils