Mimicking Polymer Processing Conditions on the Meso-Scale: Relaxation and Crystallization in Polyethylene Systems after Uni- and Biaxial Stretching

TL;DR

This paper explores how stretching and cooling affect the structure of polyethylene, revealing how these processes influence crystallization and chain ordering.

Contribution

The study introduces mesoscale MD models to investigate processing-property relations in polyethylene under various stretching and cooling conditions.

Findings

Crystal growth occurs mainly in regions without entanglements.

Biaxial stretching and cooling procedures significantly affect chain ordering and crystallization.

Orientation and crystallization behavior are influenced by stretching directions and cooling rates.

Abstract

Highly varying process conditions drive polymers into nonequilibrium molecular conformations. This has direct implications for the resulting structural and mechanical properties. This study rigorously investigated processing-property relations from a microscopic perspective. The corresponding models use a mesoscale molecular dynamics (MD) approach. Different loading conditions, including uniaxial and biaxial stretching, along with various cooling conditions, were employed to mimic process conditions on the micro-scale. The resulting intricate interplay between equi-biaxial stretching, orientation, and crystallization behavior in long polyethylene chains was reviewed. The study reveals notable effects depending on different cooling and biaxial stretching procedures. The findings emphasize the significance of considering distributions and directions of chain ordering. Local inspections of trajectories unveil that crystal growth predominantly occurs in regions devoid of entanglements.

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