Crystallization kinetics and melting behaviors of nylon 6/foliated graphite nanocomposites

Abstract

This article studies the crystallization kinetics and melting behaviors of nylon 6/foliated graphite electrically conducting nanocomposites. The crystallization kinetics under isothermal conditions is described by the Avrami equation. The values of the exponent found for the neat nylon 6 and the nanocomposite samples are about 3.0 and 1.2, respectively. For non-isothermal studies, the Avrami equation modified by Jeziorny, the Ozawa theory, the modified Ozawa equation and an equation combining the Avrami and Ozawa equation are employed. It is found that the Ozawa analysis fails to provide an adequate description of the non-isothermal crystallization process in both the neat nylon 6 and the nanocomposite samples. While the combination of Avrami and Ozawa equations exhibit great advantages in treating the non-isothermal crystallization kinetics. The activation energies are also determined by the Arrhenius relation and the Kissinger method for isothermal and non-isothermal crystallization, respectively. In both cases, the activation energy for the nanocomposite sample is greater than that for the neat nylon 6. In addition, subsequent DSC scans have also been performed to investigate the melting behaviors of the isothermally and non-isothermally crystallized samples. Results reveal that the isothermally crystallized samples exhibit two melting endotherms, while only the neat nylon 6 sample shows two melting endotherms after non-isothermal crystallization. The equilibrium melting temperature obtained is lower for the nanocomposite sample than for the neat nylon 6.