Comparison of the pyrolysis behavior of PC, ABS and PC/ABS

Three types of plastics—polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS), and PC/ABS blend—were studied in this work. Kinetic analyses were performed using the Flynn-Wall-Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) methods. The evolved volatiles during the pyrolysis of each material were analyzed, and the pyrolysis behavior was proposed using in-situ tools such as thermogravimetric analyzer-Fourier transform infrared spectroscopic (TG-FTIR) and gas chromatographic separation and mass spectrometry detection (Py-GC/MS). The three samples were also pyrolysed in a fixed bed reactor to elucidate the impact of secondary reaction. For PC, the activation energy increases as the reaction progresses. PC primarily generated CO₂ and oxygenated compounds. For ABS, the activation energy experienced a slight decrease once the depolymerization reaction initiates, while a reversed trend can be observed at higher conversion rates. ABS pyrolysis mainly produced nitrogen-containing compounds and mono-aromatics. In the case of PC/ABS blend, a distinctive two-stage decomposition mechanism was observed. The interaction between PC and ABS in the blend promoted the formation of N/O-containing compounds. Additionally, this interaction enhanced the production of lighter phenols at the expense of bisphenol A, while ABS was not affected markedly. Stronger re-condensation and cracking reactions in the fixed bed system, facilitated the formation of poly-aromatics and lighter phenols (p-cresol and 4-ethylphenol) at the expense of bisphenol A during the pyrolysis of PC. In contrast, styrene from ABS decomposition was weakly affected by the secondary reaction. The intensified secondary reactions occurring the sample bed of the fixed bed experiments can also enhance the interaction between volatiles from ABS and PC, forming more heterocyclic N-compounds.