Crystallization kinetics and annealing behavior of a thermotropic liquid crystalline polymer

Isothermal crystallization kinetics of DuPont liquid crystalline polymer HX4000 were analyzed using differential scanning calorimetry. As in VECTRA type LCPs, there seem to be two crystallization processes in this polymer: a fast process and a slow process. The fast process is as fast as heat transfer and gives crystals with a broad melting peak at ca. 317°C. The slow process can be analyzed using the Avrami equation and generates crystals with a sharp melting peak at a lower temperature than those of the fast process. A new model for the crystallization of rod-like macromolecules was developed by considering a combination of disc-like and fibrillar growth. The proposed model was supported by the results of Avrami analysis and X-ray analyses.

DSC results similar to those produced by this slow process could be produced by annealing. The origin of the low temperature peak was investigated using wide and small angle X-ray techniques. By assuming the existence of condis crystal-crystal transition, all remaining results could be explained.