Determination of the pyrolytic degradation kinetics of virgin-PVC and PVC-waste by analytical and computational methods

Thermogravimetric curves of virgin- and waste-PVC in an atmosphere of nitrogen and nitrogen saturated with water vapour were recorded at several heating rates to determine degradation kinetics. The degradation curves of virgin-PVC showed two stages of considerable mass loss. Application of the Friedman method to the experimental data proved to be too inaccurate to determine the kinetics unambiguously. Numerical determination of the kinetics parameters resulted in a better description of the data. Two models were fitted to a set of degradation curves of virgin-PVC. Both models showed good reproducibility. The effects of addition of water vapour to the atmosphere were limited to very high temperatures. The degradation curves of rigid PVC-waste showed an additional mass loss between 950 and 1150 K, presumably caused by limestone conversion. The model proposed to describe the degradation of rigid PVC-waste fitted the experimental curves well. Samples from PVC-waste pipes proved to be too heterogeneous to fit the degradation curves with one set of parameters.