Influence of graphene on thermal degradation and crystallization kinetics behaviour of poly(lactic acid)

In present study, the effect of graphene (GR) on crystallization and thermal degradation kinetic behavior of poly(lactic acid) (PLA) was investigated. The non isothermal cold crystallization kinetic study for PLA-GR nano-composites was carried out using differential scanning calorimetry at different heating rates of 2.5, 5, 7.5 and 10 degrees C/min. The obtained kinetic data were analyzed using crystallization kinetic models such as Avrami and Tobin methods. The decreasing trend obtained in the Avrami as well as Tobin exponent (n and n(T), respectively) with respect to neat PLA revealed the nucleating effect of graphene. Thermal degradation behavior of both PLA and PLA-GR nanocomposites was also analyzed by Kissinger method. The increasing trend in the activation energy with respect to GR loading was observed as compared to neat PLA. This is an indication of improvement in the thermal stability of PLA with an increase in the GR loading. Polarized optical microscopy (POM) was used to observe the growth of spherulites in the PLA and PLA-GR nanocomposites. With respect to addition of GR in the PLA matrix, reduction in the nucleation induction time and an increment in the number of nucleation sites were reflected in the POM analysis.