Rheo-optical measurements of the first and third normal stresses of homopolymer poly(vinyl methyl ether) melt

Ajay Kulkarni, Semen Kharchenko, Rangaramanujam M. Kannan

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Normal stresses play a key role in polymer processing, yet accurate measurements are still challenging. Simultaneous rheo-optical measurements are conducted on a poly(vinyl methyl ether) homopolymer melt over a wide range of temperatures and oscillatory shear frequencies, in an effort to measure the normal stresses, by using quantitative flow birefringence measurements. The stress optical rule holds well for this polymer as expected, with the value of the stress optic coefficient of (6.38±0.19)×10-11 cm2/dyn at 30°C. The first and third normal stress difference coefficients ψ1*, ψ3 * calculated using a single memory constitutive equation applied to the stress and birefringence data, are in excellent agreement. The ratio of the measured third and first normal stress difference coefficients, (1-β)=0.71±0.05, agrees well with the result of the Doi-Edwards model with independent alignment approximation (β=0.28). The measurement of normal stress difference coefficients with such small deviations proves the robust nature of the improved rheo-optical instrument and its ability to measure complete stress tensor.

Original languageEnglish (US)
Pages (from-to)951-958
Number of pages8
JournalRheologica Acta
Issue number6
StatePublished - Aug 2006
Externally publishedYes


  • First and third normal stress difference
  • Poly(vinyl methyl ether)
  • Rheo-optics
  • Stress optic coefficient

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanics of Materials
  • Chemical Engineering (miscellaneous)
  • General Materials Science


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