BLENDS OF A THERMOTROPIC LIQUID-CRYSTAL POLYESTER WITH POLY(PHENYLENE SULFIDE)

Blends of a thermotropic liquid-crystalline polymer (LCP), based on a copolyester of hydroxynaphthoic acid and hydroxybenzoic acid, with an engineering thermoplastic, poly(phenylene sulphide) (PPS), were prepared using a co-rotating twin-screw extruder. The blends were subsequently injection moulded to study their mechanical, dynamic, impact and morphological characteristics. Rheological studies have indicated a higher shear viscosity of the LCP as compared to PPS, with the shear viscosity of some of the blends being higher than that of the LCP. Dynamic and thermal studies have indicated overlapping temperature transitions of the pure components. Therefore, based on these measurements it is not possible to make a conclusion about the compatibility of the blends. Thermogravimetric studies have indicated the poor thermal stability of the blends when compared to the pure materials. The tensile and impact properties of these blends were found to increase with the addition of LCP. However, the pure LCP exhibits the highest properties. The morphology of the blends has indicated their incompatibility and the formation of LCP droplets in the matrix of PPS at nearly all concentrations of LCP, with the formation of the skin-core morphology being clearly visible at LCP content greater than 25%.