Properties of fibres spun from blends of a thermotropic liquid crystalline block copolymer with poly(ethylene terephthalate)
Triad4-co-PBT, a thermotropic liquid crystalline (TLCP) block copolyester has been blended with fibre grade poly(ethylene terephthalate) (PET) to investigate the potential ofin-situ fibre reinforcement. Fibres containing 5 to 80 wt.% TLCP were extruded and the effects of processing conditions were studied, e.g. spinning temperature and post treatment conditions. The fibres were evaluated for mechanical performance, dimensional stability (shrinkage) and development of shrinkage stresses. The optimal processing temperature for these blends was determined to be between 270 - 275°C based on mechanical performance and their fibre WAXS diffraction patterns. The optimal blend composition was found to be 10 wt.%. The highest modulus (19.8 GPa) was achieved with a 20 wt.% blend, but this system had a low ultimate strength (725 MPa) and numerous defects in the cold drawn fibre. A study of the post treatment process revealed that fibres drawn at 220°C exhibited increased thermal stability independent of TLCP content compared to those drawn at lower drawing temperature. Scanning electron microscopy of fractured fibre cross sections revealed a two phase morphology with the LCP phase dispersed as fine spherical particles