engleski

Kinetic triplet evaluation of the non-isothermal degradation of aliphatic-aromatic copolyester

Non-isothermal thermogravimetric (TG) analysis has been widely used to investigate the kinetics and the mechanism of degradation processes of many materials, including polymers. In the present work the non-isothermal TG analysis of aliphatic-aromatic copolyester (AAC) produced from 1, 4-butanediol, terephtalic acid and adipic acid was carried out over the temperature range 50-650°C at four heating rates (2, 5 ; 5 ; 10 and 20°C/min) in the nitrogen atmosphere. The invariant kinetic parameters method (IKP) in combination with isoconversional methods (Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose) was used to determine the invariant kinetic parameters, i.e. the activation energy (Einv) and the pre-exponential factor (Ainv). The IKP method is applied on the conversion range 0, 20≤ alpha≥ 0, 85 in which the E values obtained by isoconversional methods are practically constant. To obtain Einv and Ainv 17 kinetic models were considered. In order to explain the thermal degradation of the investigated materials, it is necessary to know the entire kinetic triplet, i.e. E, A and the conversion function, f(alpha). The values of Einv and Ainv obtained by IKP method were used for numeric evaluation of f(alpha). The dependence of the curve f(alpha) vs. alpha can not be fitted precisely by any ideal kinetic model, but its shape led us to the true f(alpha) characteristic for the mechanism of non-isothermal degradation of AAC.

IKP method; Flyn-Wall-Ozawa; Kissinger-Akahira-Sunose; kinetic triplet; non-isothermal thermogravimetry

nije evidentirano