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Nonlinear viscoelastic predictions of uniaxial‐extensional viscosities of entangled polymers
Author(s) -
Pattamaprom C.,
Driscroll J.J.,
Larson R.G.
Publication year - 2000
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/1521-3900(200008)158:1<1::aid-masy1>3.0.co;2-v
Subject(s) - viscoelasticity , extensional viscosity , viscosity , dispersity , materials science , extensional definition , polymer , nonlinear system , thermodynamics , parametric statistics , reptation , mechanics , polymer chemistry , composite material , physics , mathematics , geology , paleontology , quantum mechanics , shear viscosity , tectonics , statistics
A simplified version of a convective‐constraint‐release model by Mead, Larson, and Doi 1) is used here for predicting steady‐state viscoelastic properties of linear polydisperse polymers in uniaxial extensional flow. The model predictions are compared with linear dynamic viscosities and steady‐state uniaxial extensional viscosities of polystyrenes for which GPC measurements of the molecular weight distribution were reported 2) . By using parameter values obtained from data for monodisperse polystyrenes, the predictions for the polydisperse samples are made without adjustable parameters. For well‐entangled samples, good agreement is obtained for both linear viscoelastic and extension‐thinning regimes. For a weakly‐entangled sample 3) , a transition from extension thinning to extension thickening as the extension rate increases appears to be correctly predicted by the model. The effects of constraint release are pronounced in the stretch ratio and viscosity contribution from each component to the overall viscosity.