Kinetic study of thermal degradation of poly(l-lactide) filled with β-zeolite

Abstract

The thermal features and decomposition kinetics of poly(l-lactide) (PLA) filled with β-zeolite have been studied through differential thermal analysis measurements and thermogravimetric analysis. The experimental data were collected under nitrogen atmosphere with the heating rates of 5–30 K min−1, and the thermal degradation of PLA/β-zeolite composites is observed to mainly occur in the temperature range of 550–675 K. The incorporation of β-zeolite has been found to make the onset thermal decomposition temperature of PLA obviously decrease. With the Flynn–Wall–Ozawa method, the activation energy E a of the composites has been estimated and the β-zeolite composites have required higher E a values for thermal decomposition reaction than pure PLA. The pre-exponential factor ln A can be readily obtained so as to establish the thermal conversion curves if the first-order mechanism is taken. Simulated results reflect that the first-order reaction mechanism has led to certain large deviations at the low conversion levels. By scanning the well-known 27 mechanism functions, the D5 mechanism of Zhuravlev, Lesokhin, Tempelman equation is found to be the most suitable mechanism for the description of the thermal decomposition of PLA and its β-zeolite counterparts. Along with the Flynn–Wall–Ozawa method, the D5 mechanism has performed excellently to establish all the conversion curves over the whole range, resulting in more satisfactory simulation results than the first-order reaction mechanism.