Thermogravimetric pyrolysis of waste polyethylene-terephthalate and polystyrene: A critical assessment of kinetics modelling

Limitations of model-fitting methods for kinetic analysis: Polystyrene thermal degradation

“…The selected conversion function, f(α), corresponds to a L2 chain scission kinetic model, as described elsewhere (Sanchez-Jimenez et al , 2010). All four simulated curves have been fitted to some of the most common kinetic models using the same Coats-Redfern integral method employed in Brems' work (Brems et al , 2011). The resulting plots are shown in Figure 2.…”

“…When dealing with real experimental data it is common to restrict the fit to data within a limited range of conversion because the low and high ends of the conversion range are often distorted due to experimental errors. Such restriction was also employed in Brems' paper (Brems et al , 2011). Thus, we have carried out the fitting procedure using data within the range 0.1≤α≤0.9.…”

“…An important volume of work has been devoted to the determination of the activation energy and kinetic model describing the thermal degradation of polystyrene (Brems et al , 2011, Chen et al , 2007, Chen and Vyazovkin, 2006, Faravelli et al , 2001, Peterson et al , 2001, Sanchez-Jimenez et al , 2012, Snegirev et al , 2012, Sterling et al , 2001, Westerhout et al , 1997. However, results show a wide divergence in the activation energy values and the kinetic models proposed.…”

“…Also, both complex and one-step mechanisms are suggested. A recent paper questions the application of general kinetic models such as diffusion or nucleation for the kinetic analysis of polymer pyrolysis (Brems et al , 2011). In that paper, the pyrolysis of polystyrene is studied by fitting the experimental data, recorded under dynamic heating conditions, to some of the most widely used  Corresponding author.…”

“…Actually, since its publication, we have found a number of polymers such as cellulose, polystyrene and polybutylen terephtalate, that decompose according to a random scission model (Sanchez-Jimenez et al , 2010, Sanchez-Jimenez et al , 2011, Sanchez-Jimenez et al , 2012. Here, we attempt to provide some insight about the use of model-fitting methods and highlight some of its limitations in order to clarify why in some cases the experimental data cannot be properly fitted by any kinetic model (Brems et al , 2011).…”