BLENDS OF THERMOTROPIC LIQUID-CRYSTALLINE POLYESTERS AND POLY(BUTYLENE TEREPHTHALATE) - THERMAL, MECHANICAL, AND MORPHOLOGICAL PROPERTIES

Blends of poly(butylene terephthalate) (PBT) with three different ther motropic liquid crystalline polyesters (TLCPs) were prepared. The firs t TLCP (HBH-6) consists of diad aromatic ester type mesogenic units an d the hexamethylene spacers along the main chain, and the second (TB-S 6) is a wholly aromatic polyester TLCP having alkoxy side groups on th e terephthaloyl moiety. The last (TR-4,6) is an LC copolymer consistin g of triad aromatic ester type mesogenic units and two different space rs; tetramethylene and hexamethylene units. Blends of TLCP with PET we re melt spun at different LCP contents and different draw ratios to pr oduce monofilaments. For the HBH-6/PBT and TB-S6/PBT blends, the ultim ate tensile strength showed a maximum value at the 5 wt% level of LCP in the blends, and then it decreased when the LCP content was increase d up to 20%. On the other hand, the initial modulus monotonically incr eased with increasing LCP content in all cases. The blends with TB-S6 showed the highest tensile properties of the three blend systems. This can be ascribed to the highest rigidity of the polymer chain, which s till carries relatively long alkoxy substituents that promote sufficie nt adhesion between the LCP and PET matrix. When compared with the PET fiber itself, the fibers obtained from the 5% TB-S6/PBT blend exhibit ed an improvement in tensile strength by > 250% and in tensile modulus by similar to 200%.