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Kinetic study of thermal degradation of high-impact polystyrene nanocomposites with different flame retardants using isoconversional and model fitting methods

The non-isothermal degradation of pure high- impact polystyrene (HIPS) and flame retarded HIPS nanocomposites was investigated in the temperature range 25–550 °C at four heating rates in an inert atmosphere. Three different phosphate and polyphosphate based flame retardants were used, while nanosilica and montmorillonite clay were used as nanofillers. Kinetic analysis was performed using isoconversional and model fitting non-linear regression method. Activation energy (Ea) was determined by isoconversional methods of Friedman and Kissinger- Akahira-Sunose while true kinetic triplets (Ea, A, f(α)) were determined by one step and two-step non-linear regression with various reactions mechanisms. It was found that flame retarded samples exhibit complex degradation which cannot be satisfactorily described by single reaction model fitting. Instead, when each distinctive degradation step was modelled individually it was possible to obtain good fit with Reaction order and Avrami-Erofeev proposed mechanisms while the same was not possible for Diffusion and Autocatalytic mechanisms

flame retardants ; high-impact polystyrene ; non-isothermal degradation kinetics ; nonlinear regression ; thermogravimetric analysis

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