Thermal Properties and Morphology of Liquid Crystalline Copolyester and Polyester Elastomer Blends

Abstract

Polyester elastomer (PEL) blends having a hard segment of polyester (PBT), soft segment of polyether (PTMG), and a liquid crystalline copolyester (LCP), poly(benzoate-naphthoate) were prepared with a twin-screw extruder. Test specimens for thermal properties were prepared by injection molding. Rheological properties and morphology were investigated by Instron capillary rheometer (ICR) and scanning electron microscopy (SEM). Thermal properties of the LCP/PEL blends were investigated by DSC, dilatometer, heat deflection temperature tester, and a Rheovibron viscometer. DSC study revealed a partial miscibility between LCP and PEL. It was found that the LCP acted as a nucleating agent for the crystallization of PEL in the LCP/PEL blends. The dimensional and thermal stability of the blends were increased by increasing the LCP cont-ent. The storage modulus (E' was improved by increasing the LCP content. The blend viscosity showed a minimum value at 5 wt% of LCP which increased by increasing the LCP content above 5 wt% of LCP The morphology of the LCP/PEL blends showed poor interfacial adhesion between the two phases, and the fibrillar structure of LCP phase in the matrix was affected by the LCP content, shear rate, and extrusion temperature. The morphology of the blends was found to be affected by their compositions and processing conditions.