Thermal Cracking of Virgin and Waste Plastics of PP and LDPE in a Semibatch Reactor under Atmospheric Pressure

Study of the decomposition kinetics, pyrolysis products, and even reaction mechanisms plays an important role for the development of polymer recycling. In the present research, the kinetics of virgin and waste polypropylene (PP) and low-density polyethylene (LDPE) were studied by a modified Coats–Redfern method. Afterward, thermal cracking of them in a semibatch reactor under atmospheric pressure in nitrogen has been investigated. Both virgin and waste plastics are decomposed at 420–460 °C, and the products have been characterized using GC, FT-IR, 1H NMR, and GC-MS. The reaction path and the degradation mechanism for the thermal cracking of polymer in this study were also discussed. The lower activation energy of waste PP and LDPE indicates that waste plastics degrade at lower initial temperature and may favor mild conditions. Due to the short residence time, the higher gaseous and liquid yields were obtained for virgin PP and LDPE. A large amount of residues for waste polymer indicates that it is a favor...

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