Characterization of thermal behavior and kinetics of crystallization of a thermotropic rigid‐chain copolymer

Abstract

AbstractThermal analysis was employed to estimate the heat of transition, equilibrium melting temperature and surface free energy of a thermotropic liquid crystal copolyester resin (70 mol% p‐hydroxybenzoic acid and 30 mol% 2,6‐hydroxynaphthoic acid). Specific heats and melting and crystallization behavior were evaluated using differential scanning calorimetry (DSC). Experiments over a wide range of cooling rates indicate two different crystallization processes: a rapid crystallization process and a slow crystallization process. The kinetics of the rapid crystallization process were evaluated using a non‐isothermal method. The analysis indicates that the rapid crystallization process can be suitably described by the non‐isothermal Avrami equation. The Avrami exponent is found to be equal to 2, which is in agreement with the nucleation and growth mechanism of the rigid rodlike molecules. The kinetics of the slow crystallization process, which were studied using an isothermal method, indicate that the degree of crystallinity varies linearly with log(time). The equilibrium melting temperature for this process is found to be 372°C. The Arrhenius plot yields a linear relationship in the lower temperature range.