Okpeafoh S. Agimelen, Peter D. Olmsted
Recent step strain experiments in well-entangled polymeric liquids demonstrated a fracture-like phenomenon that was interpreted in terms of a massive loss of entanglements after yielding. This was taken, in these experiments, to signify the invalidity of the Doi-Edwards (DE) tube model. We have investigated this phenomenon using the Rolie-Poly equation, which approximates a successful version of the DE theory, and we find close quantitative agreement with the experiments, as well as with the proposal by Marrucci and Grizzuti in 1983 that entangled polymer liquids possess an elastic instability. The fracture is a transient manifestation of this elastic instability that relies on the amplification of spatially inhomogeneous fluctuations. It resembles spinodal decomposition, with strain playing the role of the conserved quantity.
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http://arxiv.org/abs/1204.4169
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