Nonisothermal Crystallization Behavior of Poly(m-xylene adipamide)/Montmorillonite Nanocomposites

This article reports the nonisothermal crystallization behavior of MXD6 and its clay nanocomposite system (MXD6/MMT) using differential scanning calorimetry (DSC). The DSC experimental data were analyzed by theoretical modeling of the crystallization kinetics using the Avrami, Ozawa, Jeziorny, and the combined Avrami―Ozawa semiempirical models. It has been determined that these models adequately described the crystallization behavior of the MXD6 nanocomposite at cooling rates below 20 °C/min, but there was a deviation from linear dependence at higher cooling rates. This was attributed to changes of both the free energy and the cooling crystallization function K(T) over the entire crystallization process, as well as possible relaxation effects leading to structural rearrangements. In addition, the activation energy determined using the differential isoconversional method of Friedman was also found to vary, indicating changes in both the free energy and crystallization mechanism. Despite the lack of a reliable theoretical model, the heterogeneous nucleating activity of the MMT nanoparticles was demonstrated and quantified using Dobreva's method (Φ = 0.71), and the crystallization rate for the nanocomposite system was found to be greater than pure MXD6 by up to 79% at 40 °C/min.