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Study on Rheological Properties of HBA/HNA Thermotropic Liquid Crystalline Polymer

HBA/HNA계 열방성 액정고분자의 유변학적 특성에 관한 연구

  • Son, Young-Gon (Division of Advanced Materials Science and Engineering, Kongju National University)
  • 손영곤 (공주대학교 공과대학 신소재공학부)
  • Received : 2010.11.26
  • Accepted : 2010.12.17
  • Published : 2010.12.31

Abstract

Rheological measurement of a thermotropic liquid crystalline poymer (TLCP) is not an easy task since their rheological responses are strongly influenced by a thermal history during a processing and thus the reproducibility of the measurement is poor. In order to find out a cause for the strong influence of the thermal history, rheological measurements and DSC observations of the TLCP having various thermal histories were carried out. It was observed that the TLCP used in this study shows liquid-like behavior at a temperature above a crystal-nematic transition temperature ($280^{\circ}C$), but at the same time crystallization can occur at this temperature range and as a consequence the viscosity of the polymer continuously increases. When the samples are heated beyond the $320^{\circ}C$, all crystals thus formed and the thermal histories were observed to disappear. Crystallization rate of the samples annealed above $320^{\circ}C$ was very low at even the lowed temperature ($280^{\circ}C\;{\sim}\;320^{\circ}C$). Therefore, it is concluded that rheological measurements of TLCP used in this study must be performed after annealed above the nematic-isotropic transition temperature for better reproducibility.

Keywords

HNA/HBA thermotropic liquid crystalline polymer;Rheological variation;Thermal history

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