FORMATION, STABILITY, AND PROPERTIES OF IN-SITU COMPOSITES BASED ON BLENDS OF A THERMOTROPIC LIQUID-CRYSTALLINE POLYMER AND A THERMOPLASTICELASTOMER

This paper describes the preparation and properties of in-situ composi tes based on polymers with no overlap in processing temperatures. The polymers used were Vectra A900, a thermotropic liquid crystalline copo lyester (TLCP), and Arnitel em630, a thermoplastic elastomer. Blends w ere generated by feeding the two components from separate extruders in to a Ross static mixer. Different morphologies were obtained by varyin g the number of mixing elements of the static mixer. Using 8 mixing el ements led to a stratified morphology of Vectra layers in Arnitel, usi ng 11 mixing elements resulted in the desired continuous fiber/matrix morphology whereas a pronounced skin-core morphology was obtained with 14 mixing elements. It is argued that in-situ composites can be gener ated by a distributive mixing process without the formation of an Inte rmediate droplet/matrix morphology as occurs in common dispersive blen ding equipment. Tensile modulus and strength of all blends increased w ith extrudate draw ratio as a result of increased molecular orientatio n of the TLCP phase. The level of reinforcement, however, was lower th an expected, probably due to the low temperature of drawing. Annealing and capillary instability experiments showed that above the melting p oint of the TLCP the fiber/matrix morphology rapidly breaks up into a droplet/matrix morphology. This process takes just a few seconds for f ibers of thickness similar to 1 mu m. It is shown to be the probable c ause of the skin-core morphology obtained in case of 14 mixing element s.