Structure and properties of injection molded blends of liquid crystal polymer (40 PET/60 PHB) with poly(butylene terephthalate)

Abstract

Blends of a poly(butylene terephthalate) (PBT) and a liquid crystalline polymer (LCP) were prepared in a single screw extruder. The LCP used was a liquid crystalline copolyester of 40% polyethylene terephthalate with 60% p-hydroxybenzoic acid (40 PET/60 PHB). Specimens for mechanical testing were prepared by injection molding. Rheological, morphological, microstructural, and mechanical properties were investigated by capillary rheometry, polarized light microscopy, x-ray diffractometry, and a tensile tester, respectively. For the LCP content higher than 5 wt. % a significant decrease of the viscosity was noted. The morphology of the dispersed LCP phase varies between droplets and oriented fibrils. The degree of cystallinity of PBT and the crystal sizes were found to be affected by LCP addition. The tensile mechanical behavior of the PBT + LCP blends was also found to be affected by their compositions. The elasticity modulus and the parameter of elasticity anisotropy monotonically increase with the LCP content. The strain at break shows a drastic decrease for the blends containing more than 10 wt. % LCP. The long-term creep test shows that the creep compliance decreases noticeably when the LCP content increases.