Creep measurements confirm steady flow after stress maximum in extension of branched polymer melts
Nicolas J. Alvarez, José Manuel Román Marín, Qian Huang, Michael Locht Michelsen, and Ole Hassager
Accepted
We provide conclusive evidence of non-monotonic mechanical behavior in the extension of long-chain branched polymer melts. While non-monotonic behavior is known to occur for solids, for the case of polymeric melts, this phenomenon is in direct contrast with current theoretical models. We rule out the possibility of the overshoot being an experimental artifact by confirming the existence of steady flow after a maximum under both constant stress and constant strain rate kinematics. This observation indicates the omission of important physics from current models for these industrially important materials, whose processing properties depend on extreme molecular extension.