Molecular orientation in channel flows of main-chain thermotropic liquid crystalline polymers

Jr Cinader, W. R. Burghardt*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

In situ wide angle X-ray scattering is employed for quantitative measurements of flow-induced molecular orientation in channel flows of thermotropic hydroxypropyl-cellulose (HPC). An extrusion die, constructed to allow X-ray access, generates slit flow, slit flow with superimposed contractions and expansions in cross-section, and slit flow past an obstruction. In slit flow, weak molecular orientation develops slowly with downstream position. Superimposed extension associated with contraction flows leads to a strong enhancement in orientation, which persists with distance further downstream of the contraction. Conversely, transverse extension present in expansion flows generates a bimodal orientation state and substantial reductions in average molecular orientation. These results are compared to earlier measurements on a commercial fully aromatic thermotrope. HPC is found to respond more strongly to superimposed extension, and more weakly to the prevailing inhomogeneous shear flow than the commercial material.

Original languageEnglish (US)
Pages (from-to)247-258
Number of pages12
JournalRheologica Acta
Volume39
Issue number3
DOIs
StatePublished - 2000

Keywords

  • Channel flows
  • Liquid-crystalline polymer
  • Molecular orientation
  • WAXS

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics

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