Jh. Chang et al., BLENDS OF THERMOTROPIC LIQUID-CRYSTALLINE POLYESTERS AND POLY(BUTYLENE TEREPHTHALATE) - THERMAL, MECHANICAL, AND MORPHOLOGICAL PROPERTIES, Polymer engineering and science, 35(20), 1995, pp. 1605-1614
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%.