Tailoring the Molecular Weight Distribution of Polyethylene for Flow-enhanced Self-Nucleation

摘要

Fibrillar precursors of crystallization can form during short and intense pulse of shear, even at high temperature. In a bimodal polyethylene (PE) with a high molecular weight tail above 106 g/mol, shear can lead to a suspension of fibrillar precursors at temperatures about the equilibrium melting point. In the flow conditions investigated in this work, precursors generated at this high temperature tend to relax. However, we find that, on cooling, they are stabilized by crystallization and transform into shishes just below 140C, where the formation of kebabs is still suppressed because of the low undercooling. We show that shishes are ideal as a substrate for heterogeneous crystallization. In fact, they can shift the onset of crystallization, from 124C in quiescent conditions, to temperatures as high as 132C during cooling at 5C/min.