Paper Number
PM5
Session
Polymer Melts: From Molecular Rheology to Processing
Title
Unraveling dynamics of entangled polymers in strong extensional flows: An alternative to the tube model
Presentation Date and Time
October 16, 2018 (Tuesday) 11:30
Track / Room
Track 2 / Plaza I
Authors
- Moghadam, Soroush (University of Michigan, Department of Mechanical Engineering)
- Larson, Ronald G. (University of Michigan, Department of Chemical Engineering)
Author and Affiliation Lines
Soroush Moghadam1 and Ronald G. Larson2
1Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI; 2Department of Chemical Engineering, University of Michigan, Ann Arbor, MI
Speaker / Presenter
Moghadam, Soroush
Text of Abstract
The traditional Doi-Edwards tube model, when applied to strong extensional flows at strain rates above the inverse Rouse time, predicts that the tube deforms affinely, which implies the extensional stress reaches its plateau as soon as the chain has become locally fully stretched, even if the chain is still folded, and far from being completely unraveled. By starting from a state in which the chain is in a locally fully stretched, but folded state, we develop an “entangled kink dynamics algorithm” that predicts the final unraveling of an ensemble of mutually entangled, folded chains, driven by a combination of drag forces and chain tension, with negligible Brownian motion. Equations for motions of both entangled folds and unentangled folds in which two chains hook together at a single fold point, are derived and solved, including the effects of constraint release that occurs when the end of one chain passes through the fold at which that chain is entangled. This model predicts that kinks move non-affinely, that the chain tension during unfolding is much less than predicted by the tube model, and that the stress approaches a plateau stress than in the tube model. The new model shows that in the folded state for fast extension, the entangled chains act like dilute ones.