Multi-perspective kinetic analysis of plastic blends under thermogravimetric pyrolysis conditions

Plastic blends were co-pyrolyzed under non-isothermal conditions in a thermogravimetric (TG) analyzer. The co-pyrolysis characteristics and kinetic triplet, i.e., apparent activation energies, reaction models, and preexponential factors, were investigated from different perspectives, including the overall, weight-loss stage, and overlapping complex reaction deconvolution perspective. Fraser Suzuki (FS) deconvolution was adopted for the peak fitting of the differential TG curves. A model-free method and the master plot theory were used to solve the kinetic equations and fit the reaction mechanism models, respectively. The results indicated that the co-pyrolysis of plastic blends (polyvinyl chloride (PVC)/polypropylene, PVC/polystyrene, PVC/acrylonitrile-butadiene-styrene) could not be adequately described using the overall approach or the weight-loss stage approach. The pyrolysis reaction exhibited a complex multistep overlapping reaction mechanism. FS deconvolution identified and separated four pseudo-reactions from the pyrolysis reaction. The kinetic triplet of the separated reactions was estimated and used to establish kinetic rate equations. Mathematical relations were established between the mass loss rate and pyrolysis temperature. The TG curves of the co-pyrolysis of plastic blends can be parameterized and predicted using the overlapping complex reaction deconvolution model. This study can act as a basis for the development of thermal conversion of mixed plastic waste.