Thermal and spectroscopic (TG/DSC-FTIR) characterization of mixed plastics for materials and energy recovery under pyrolytic conditions

Seven waste thermoplastic polymers (polypropylene, polyethylene film, polyethylene terephthalate, polystyrene, acrylonitrile-butadiene-styrene, high-impact polystyrene and polybutadiene terephthalate, denoted as PP, PE (film), PET, PS, ABS, HIPS and PBT, respectively) and four synthetic mixtures thereof with different compositions representing commingled postconsumer plastic waste and waste of electrical and electronic equipment were studied by means of simultaneous thermogravimetry/differential scanning calorimetry coupled with Fourier transform infrared spectroscopy (TG/DSC-FTIR) under pyrolytic conditions (inert atmosphere). By summing all the heat change contributions due to physical and/or chemical processes occurring (i.e., melting, decomposition), an overall energy, defined as the degradation heat, was determined for both single component and their mixtures. It was found to be about 4-5 % of the exploitable energy of the input material. Vapors evolved during the pyrolysis of single-component polymers and their mixtures, analyzed using the FTIR apparatus, allowed identifying the main reaction products as monomers or fragments of the polymeric chain. Results from TG/DSC runs and FTIR analysis show that there is no interaction among the plastic components of the mixtures during the occurrence of pyrolysis.