THERMOTROPIC LIQUID-CRYSTALLINE POLYMERS WITH FLEXIBLE MOIETIES BLENDED WITH POLY(ETHYLENE-TEREPHTHALATE)

Several novel thermotropic liquid-crystalline polymers (TLCPs) were bl ended with poly(ethylene terephthalate) (PET) and spun into fibres in an effort to improve fibre performance and processability. The TLCPs w ere screened to determine the optimal molecular architecture for fibre enhancement and compatibilty. At concentrations up to 20 wt%, blends of the block copolymers PME-b-PET and PME-b-PBT (PME=poly(ethoxy 1,4-p henylene terephthalate), PBT=poly(butylene terephthalate)) with PET sh owed minor improvements in modulus. Another TLCP, PBEM (poly(butoxyeth oxy 1,4-phenylene terephthalate)), proved to be an excellent processin g aid for PET, since it reduced the melt viscosity of PET by approxima tely 75% at a concentration of only 2.5 wt%. The third class of TLCP i nvestigated was a 'Random Copolymer' system. At a concentration of onl y 5 wt%, this blend exhibited a 50% modulus improvement (25 GPa) and a n equivalent ultimate strength (1100 MPa) compared to neat PET fibres. SEM experiments exposed TLCP fibrils uniformly dispersed within the P ET matrix with aspect ratios ranging between 20 and 200. The thermal s tability of these fibres was similar to the PET control.