Rheology, morphology and tensile properties of thermotropic liquid crystalline polymer/polypropylene in-situ composites

Blends of various grades of polypropylene (PP) with a thermotropic liquid crystalline polymer (TLCP), namely a copolymer of p-benzoic acid and ethylene terephthalate (60/40 mole ratio) were prepared as extruded films. A thermoplastic elastomer styrene (ethylene-butylene) styrene (SEBS) was used as a compatibilizer. Melt viscosities of all specimens were measured using a plate-and-plate rheometer with oscillating mode in the shear rate region of 1 - 200 rad/s. Addition of SEBS compatibilizer resulted in an increase of the blend viscosity. Observation of the blend morphology revealed an improvement of TLCP dispersion. The TLCP fiber aspect ratio (length to diameter) in the extruded film also increased after addition of SEBS. As a result, the film modulus in extrusion direction was enhanced. The tensile strength of the film specimen was also increased due to an improvement of interfacial adhesion.