Thermal treatment of flame retardant plastics: A case study on a waste TV plastic shell sample

Abstract

In this work, the combustion and pyrolysis characteristics of a waste TV plastic shell sample were investigated using a powerful Thermogravimetric-Fourier Infrared Spectrum-Mass Spectrum (TG-FTIR-MS) technique. The decomposition mechanisms of plastic waste and fate of bromines in both thermal processes were probed as well. The TG analysis revealed that the combustion rate was larger than that of pyrolysis at temperature of 456 °C below, whereas it decreased at temperature of 456–605 °C. As a result, the total weight loss was equivalent at temperature of 605 °C for both processes. The FTIR analysis indicated the plastic combusted vigorously at 300–500 °C and 800–900 °C. As a comparison, it decomposed drastically at 300–400 °C and 500–900° in pyrolysis. The MS analysis showed that the release of brominated products HBr, CH3Br, C2H5Br, C3H5Br, C3H7Br and C3H5BrO increased with an increase of temperature and reached maximum at 400–600 °C in both thermal processes. The release intensities of larger molecules C6H5Br, C6H5BrO and C6H4Br2 were in the descending order of C6H5Br > C6H4Br2 > C6H5BrO. It was not significant in the evolved products and decomposition pathway for both thermal processes. The entire decomposition of TV plastic shell sample could be divided into three stages, taking account of the evolved products. The backbone in acrylonitrile butadiene styrene resin and tetrabromobisphenol A first broke at 350 °C below, resulting in the form of 2-bromophenol, styrene, acrylonitrile and polybutadiene. Subsequently, the resulted 2-bromophenol debrominated forming HBr, which further reacted with hydrocarbons resulting in various brominated derivates. In addition, many small molecules, including CO2, CO and CH4 were generated in this stage. Further increasing temperature to 550 °C above, larger brominated derivates decomposed and smaller molecules predominated.