In-situ Composite Film of Ther motropic Liquid Crystalline Polymer/Polypropylene: Effect of Film Drawing on Molecular Orientation and Properties

A Blend of thermoplastic, polypropylene, with a thermotropic liquid crystalline polymer (TLCP), copolyester comprising 60 mol% of p-hydroxybenzoic acid and 40 mol% ethylene terephthalate was prepared, using a twin screw extruder. Polymer blend pellets were extruded through a microtruder as thin films, using different draw ratios. Effect of film drawing on molecular orientation and properties was investigated. The order parameter of liquid crystalline domain evaluated from polarized infrared spectra was found to increase with increasing film draw ratio. Morphology of the film observed under an optical microscope revealed increasing TLCP fibre aspect-ratio. Young’s modulus of the film measured in the machine direction was found to increase significantly with increasing TLCP fibre aspect-ratio and molecular ordering. Young’s modulus of TLCP fibres embedded in PP matrix was estimated using the Halpin-Tsai equation and found to correlate linearly with the fibre aspect-ratio and the order parameter.