What is the flow activation volume of entangled polymer melts?
authors Martins, JA; Cruz, VS; Krakowiak, J; Zhang, WD
nationality International
journal COLLOID AND POLYMER SCIENCE
author keywords Tube model; Flow activation volume; Stepshear; Viscosity
keywords C-13 NMR; POLYETHYLENE; DYNAMICS; REPTATION; CHAIN
abstract We evaluate the flow activation volume in polymer melts of isotactic polypropylene and atactic polystyrene with step-shear experiments at different melt temperatures. The melt is initially sheared with constant shear rate until the attainment of a melt state with nearly constant viscosity. Perturbations to this experiment, involving shear steps in short-time intervals with decreasing rates, are induced next. Measurements of the shear stress value at each shear rate step allow the evaluation of an experimental (apparent) flow activation volume. The true flow activation volume is evaluated by extrapolating the experimental data to infinite shear stress values. The value obtained is larger than the physical volume of the chain and agrees with the volume of a tube confining chains with a molecular weight between M (n) and M (w). Besides supporting the validity of tube model, experiments based on this protocol may be used on model polymer samples, in composites with nanoparticles and in polymer blends to access the validity of mechanisms considered by flow models.
publisher SPRINGER
issn 0303-402X
year published 2012
volume 290
issue 1
beginning page 23
ending page 29
digital object identifier (doi) 10.1007/s00396-011-2519-4
web of science category Chemistry, Physical; Polymer Science
subject category Chemistry; Polymer Science
unique article identifier WOS:000298647100003
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journal analysis (jcr 2019):
journal impact factor 1.536
5 year journal impact factor 1.612
category normalized journal impact factor percentile 24.793
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