Microstructure and nematic transition in thermotropic liquid crystalline fibers and their single polymer composites

Abstract

Abstract We describe a new single polymer composite (SPC) prepared from two liquid crystalline vectran fibers. Vectran M is the as‐spun fiber while vectran HS is the high‐strength version. A study of the morphology of the pristine materials shows that the two fibers have different crystal structures. The wide‐angle X‐ray diffraction (WAXD) data confirm the presence of the so‐called pseudo‐hexagonal (PH) unit cell in vectran M, while an orthorhombic structure is revealed in the vectran HS fibers. A transition to the nematic phase is observed by in situ X‐ray diffraction at ∼277°C for the M fibers and at ∼315°C for the HS fibers. During the compaction process, the orientation of the reinforcing fibers is well maintained and the transition to a nematic phase seems to be delayed by processing at high applied pressure. Concomitantly, vectran M loses its orientation and the transition to the nematic phase disappears. Copyright © 2007 John Wiley & Sons, Ltd.