Microstructure of Carbon Nanofiber/Thermotropic Liquid Crystalline Polymer Composites

The properties and microstructure of a thermotropic liquid crystalline polymer (TLCP, Vectran V400P) were investigated in the presence of carbon nanofibers (CNF). The electrical conductivity of TLCP increased with an addition of CNFs. The thermal analysis of pure TLCP and its composites revealed that a glass transition at similar to 110 degrees C did not change significantly. However, a decrease of tensile modulus and strength was observed with the addition of CNFs. WAXD studies showed a decrease of Herman's orientation parameter, indicating reduction of anisotropy of TLCP. Further, the disruption of molecular orientation of TLCPs was inferred by SEM and TEM analysis. SEM micrographs revealed a fibrillar structure for pure TLCPs at a macro-scale (2-5 mu m). However, this structure was not observed in composites at the same scale even though micro-size fibrils (0.05 mu m) were found with the addition of CNFs. TEM micrographs displayed banded structures of pure TLCPs, but these structures were not significant in the vicinity of CNFs. These observations confirmed that a decrease of molecular alignment and disruption of fibrillar structure of TLCP, in the presence of nanofibers, are attributed to a significant decrease in tensile modulus and strength. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 2872-2880, 2009