Nonreversible Enhanced Crystallization
of Olefin Block Copolymer
Induced by Preshearing
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Abstract
In
this work, the influence of preshearing on crystallization of
olefin block copolymer (OBC) was systematically investigated. It was
found that upon an interval of melt preshear the crystallization rate
of OBC was prominently elevated which was evidenced by both nonisothermal
and isothermal crystallization results. The lamellar thickness of
OBC increased and the size of spherulites decreased after shear. Interestingly,
annealing and multiple heating and cooling experiments demonstrated
that the enhancement effect on crystallization was nonreversible.
The morphology observations suggested that preshearing caused an alteration
in mesophase structure of OBC. On the basis of our results, we speculated
that the increase in the amount of hard blocks that dissolved in the
soft-block-rich matrix induced by shear promoted the unique “pass-through”
crystallization process of OBC, which should be responsible for the
largely enhanced crystallization of sheared OBC