Advanced isoconversional and master plot analyses on non-isothermal degradation kinetics of AlN (nano)-reinforced HDPE composites

The non-isothermal degradation kinetics of polymer nanocomposites composed of high-density polyethylene (HDPE) as polymer matrix and aluminum nitride (AlN) as nanofiller has been studied at variable concentration of (nano) AlN. Field emission scanning electron microscopy was used to examine the microstructure of the HDPE polymer and the dispersion of AlN (nano) particles in it. The non-isothermal degradation kinetics of AlN (nano)/HDPE composites has been investigated by thermogravimetric analysis (TG) at multiple heating rates between 5 and 20 A degrees C min(-1). This study confirmed that the thermal stability of the filled nanocomposites is improved as compared to pristine HDPE. Thermal transport barrier effect is also enhanced with the increase in concentration of AlN (nano) loading. Dependence of activation energy on reaction extent (alpha) of the degradation process is estimated in light of 'model-free' methods (viz. Flynn-Wall-Ozawa and Starink) and advanced isoconversional approach. Ozawa's generalized time 'theta' combination of the differential master plots '' and combined [integral (theta) and differential ] master plots '' have been employed to investigate the appropriate thermal degradation mechanism(s) for AlN (nano)/HDPE composites. The results on 'FZ master plots' show that thermal decomposition of pristine HDPE follows two-dimensional diffusion mechanism, while AlN (nano)/HDPE composites undergo more complex degradation schematics, being dependent on the applied heating rates.