Exploring stress overshoot phenomenon upon startup deformation of entangled linear polymeric liquids

This work explores the picture associated with stress overshoot during sudden continual (i.e., startup) external deformation of entangled polymeric liquids and proposes a specific scaling form to depict the intermolecular interactions responsible for chain deformation. Following a previously proposed idea that the stress overshoot in startup deformation is a signature of yielding, we search for ingredients that should go into the description of the force imbalance at the yield point and show that the expression for the intermolecular locking force f(iml), derived from the characteristics associated with the yield point, can be tested against experiment. New rate-switching experiments support the proposed formula for fiml. (C) 2009 The Society of Rheology. [DOI: 10.1122/1.3208063]