Mechanical and structural properties of extruded strands of blends containing a liquid-crystalline polyester with poly(ethylene terephthalate)

Abstract

Mechanical and structural properties of extruded strands of blends of a liquid-crystalline copolyester (LCP), containing p-hydroxybenzoic acid and 2,6-hydroxynaphthoic acid, with poly(ethylene terephthalate) (PET) were investigated using tensile testing, X-ray diffraction measurements and scanning electron microscopic observation. The extruded strands of the blends consist of a crystalline and oriented LCP phase and an amorphous and unoriented PET phase. The tensile modulus increases almost linearly with increasing LCP content for the strands of the blends of more than 10% LCP content. The LCP component hardly contributes to the improvement of the mechanical tensile properties for the strands of the blends of less than 5% LCP content. The LCP phase tends to form fibrous structures, which orient almost parallel to the direction of extrusion in the blend strands. The fibrils of the LCP component become longer and thinner with increasing extension draw ratio of the blend strands. A relationship between the mechanical tensile properties and the morphology of the LCP phase in the blend strands was discussed.