posted on 2023-11-07, 20:03authored byKun Song, Lin-Feng Wu, Dong Liu, Zhe Wang
We investigate the effect of the free chain conformation
on the
flow-induced shish nucleation in lightly cross-linked high-density
polyethylene melts by comparing nucleation processes under the quasi-static
extension (QSE) and the fast extension (FE). Under the QSE, free chains
maintain their equilibrium conformations, leading to the nucleation
process being governed by the free energy change of crystallization.
In this case, the shish is formed through the chain-folding pathway,
and its length is determined by the critical nuclei (∼0.1 μm).
By contrast, the FE remarkably orients the long free chains, which
preferentially crystallize and allow the shish length to reach one
micron. Moreover, the free chain conformation also influences the
shish radius through the combined effects of the full stretch of cross-linked
chains and the orientation of free chains. These results reveal the
fundamental role of the free chain conformation in determining the
nucleation path and the morphology of shish.