NON-ISOTHERMAL KINETIC AND THERMODYNAMIC STUDIES ON POLYESTERS AT DIFFERENT VISCOSITY AVERAGE MOLECULAR MASSES

Non-Isothermal kinetics of solid-state decomposition of Polybisphenol-A-Carbonate [PC; (Mt\: 1.5 3.68 x 10 4 ) and polymethyl metacrylate [PMMA Miv1.55-3.52 x 10 4 ] has been investigated under nitrogen atmosphere in view to study the effect of molecular mass on their thermal decompositions in solid state. Thermal data deduced through simultaneous thermogravimetric-differential thermal analysis-differential thermo gravimetry [TG-DTA-DTG] was used for calculations of thermodynamic parameters through Horowitz-Metzger and coats-Redfern methods, kinetics and mechanism of degradations of each polymer at different molecular masses. [PC] showed two step decomposition with slower rate than [PMMA], which showed single step decomposition at each of molecular mass ranges. It was observed that ester linkages in [PC] backbone provided satisfactory over [PMMA] which contain ester linkages in side chain, to Horowitz-Metzger, coats-Redfern methods kinetic equations of solid-sate decompositions In general, Horowitz-Metzger methods have shown greater values of energy of activation than Coats-Redfern methods for [PC]. Both of methods have provided a wide difference in frequency factor but almost same entropy change in most of the cases* Thermodynamic and kinetic data were mostly satisfied for first order and zero order kinetics in case of [PC] whereas were not satisfactory for [PMMA].