Apparent fracture in polymeric fluids under step shear

Agimelen, Okpeafoh Stephen and Olmsted, Peter D (2013) Apparent fracture in polymeric fluids under step shear. Physical Review Letters, 110. 204503. ISSN 0031-9007

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    Recent step strain experiments in well-entangled polymeric liquids demonstrated a bulk fracturelike phenomenon.We study this instability by using a modern version of the Doi-Edwards theory for entangled polymers, and we find close quantitative agreement with the experiments. The phenomenon occurs because the viscoelastic liquid is sheared into a rubbery state that possesses an elastic constitutive instability [G. Marrucci and N. Grizzuti, J. Rheol. 27, 433 (1983)]. The fracture is a transient manifestation of this instability, which relies on the amplification of spatially inhomogeneous fluctuations. This mechanism differs from the fracture in glassy materials and dense suspensions.