Korea-Australia Rheology Journal

The Korean Society of Rheology (한국유변학회)
권호 표지

Rheological properties of some thermotropic liquid crystalline polymers

  • Published : 2003.09.01
Download PDF
⟨ Previous Next ⟩

Abstract

Rheometry testing and the DSC measurement of five thermotropic liquid crystalline polymers (TLCP) have been carried out. The dynamic viscosities of the five TLCPs show a typical shear-thinning behaviour obeying the power-law with the power indices from 0.2 to 0.3. When these TLCPs are heated above the melting temperatures determined by the DSC measurements, the dynamic viscosities first rapidly decrease by 2～3 orders of magnitude then level off, finally increase gradually with the further increasing of temperature. The steady shearing exhibited the same behaviour as the dynamic shearing, but serious edge fracture of material slippage out of the plates occurred. The abnormal temperature dependence of the viscosities can be explained by the nematic-isotropic transition. By using the concept of activation energy, we propose a simple model which can fit the shear-thinning behaviour quite well and predict qualitatively correct temperature effects.

Keywords

References

  1. Transport Phenomena Bird,R.B.;W.E.Stewart;E.N.Lightfoot
  2. Polymer v.42 Flow induced chain alignment and disentanglement as the viscosity reduction mechanism within TLCP/HDPE blends Chan,C.K.;C.Whitehouse;P.Gao;C.K.Chai https://doi.org/10.1016/S0032-3861(01)00265-8
  3. Polym. Eng. Sci. v.36 Rheology of low nematic transition temperature thermotropic liquid crystalline copolyester HBA/HQ/SA Gao,P.;X.H.Lu;C.K.Chai https://doi.org/10.1002/pen.10677
  4. J. Non-Newt. Fluid Mech. v.13 Stress relaxation after oscillatory shear in a thermotropic liquid crystalline polymer Graziano,D.;M.R.Mackley https://doi.org/10.1016/0377-0257(83)80023-8
  5. J. Non-Newt. Fluid Mech. v.86 Rheology and miscibility of thermotropic liquid crystalline polymer blends Hsieh,T.T.;C.Tiu;G.P.Simon;R.Y.Wu https://doi.org/10.1016/S0377-0257(98)00200-6
  6. Rheol. Acta v.38 Edge fracture in cone-plate and parallel plate flows Keentok,M.;S.C.Xue https://doi.org/10.1007/s003970050184
  7. Polymer v.40 The crystallization behavior of blends of thermotropic liquid crystalline polymers McLeod,M.A.;D.G.Baird https://doi.org/10.1016/S0032-3861(98)00592-8
  8. Chem. Eng. Comm. v.53 Effect of temperature on the rheology of polymeric liquid crystals Mewis,J.;P.Moldenaers https://doi.org/10.1080/00986448708911881
  9. J. Rheol. v.38 Rheology of region I flow in a lyotropic liquid-crystal polymer: the effects of defect texture Walker,L.;N.Wagner https://doi.org/10.1122/1.550557
  10. J. Non-Newt. Fluid Mech. v.44 Transient elongational flow behavior of thermotropic liquid crystalline polymers Wilson,T.S.;D.G.Baird https://doi.org/10.1016/0377-0257(92)80046-Z