| Tensile stress and flow-induced birefringence have been measured during the uniaxial elongation at constant strain rate of two polystyrene melts with narrow molecular weight distribution. For both melts, the stress optical rule (SOR) is found to be fulfilled up to a critical stress of 2.7 MPa, independent of strain rate and temperature. Estimation of the Rouse times of the melts, from both the zero-shear viscosity and the dynamic shear moduli at high frequency, shows that the violation of the SOR occurs when the strain rate multiplied by the Rouse time of the melt exceeds approximately 3. The presented results indicate that in contrast to current predictions of molecular theories, the regime of extensional thinning observed by Bach et al. (2003) extends well beyond the onset of failure of the SOR, and therefore the onset of chain stretch in the non Gaussian regime.
for LaTeX users @article{CLuap2005-45,
author = {C. Luap and C. Müller and T. Schweizer and D. C. Venerus},
title = {Simultaneous stress and birefringence measurements during uniaxial elongation of polystyrene melts with narrow molecular weight distribution},
journal = {Rheol. Acta},
volume = {45},
pages = {83-91},
year = {2005}
}
\bibitem{CLuap2005-45} C. Luap, C. Müller, T. Schweizer, D.C. Venerus,
Simultaneous stress and birefringence measurements during uniaxial elongation of polystyrene melts with narrow molecular weight distribution,
Rheol. Acta {\bf 45} (2005) 83-91.CLuap2005-45
C. Luap, C. Müller, T. Schweizer, D.C. Venerus
Simultaneous stress and birefringence measurements during uniaxial elongation of polystyrene melts with narrow molecular weight distribution
Rheol. Acta,45,2005,83-91 |
mk@mat.ethz.ch
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