Crystallization of cross-linked polyethylene by molecular dynamics simulation

The crystallization of polymers is not, despite its importance in science and engineering, entirely understood due to the challenge of tracking the behavior of individual polymer chains in the crystallizing melt. However, increasing computational resources have brought the crystallization process wi...

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Bibliographic Details
Published in:Polymer (Guilford) 2019-05, Vol.171, p.80-86
Main Authors: Paajanen, Antti, Vaari, Jukka, Verho, Tuukka
Format: Article
Language:English
Subjects:
Chains (polymeric)
Computation
Computer applications
Computer simulation
Cross-linked polyethylene
Cross-linking
Crystal growth
Crystallization
Crystals
Molecular dynamics
Nucleation
Polyethylene
Polymers
Simulation
Supercooling
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Summary:The crystallization of polymers is not, despite its importance in science and engineering, entirely understood due to the challenge of tracking the behavior of individual polymer chains in the crystallizing melt. However, increasing computational resources have brought the crystallization process within reach of molecular simulations, and several groups have published simulations of crystal nucleation and growth in polymers. Yet, these studies have focused on linear polymer chains, and no results have been reported on cross-linked polymers, which are common in everyday applications. Here, we perform molecular dynamics simulations of the homogeneous crystallization of cross-linked polyethylene at high undercooling. Large cross-link densities cause the crystallization to slow down and reduce the final degree of crystallization. As expected, cross-links are rejected from the crystals into the amorphous phase. We observe that at all cross-link densities the intercrystalline amorphous phase is characterized by a single distribution of free segment lengths (amorphous segments with no cross-links). The findings provide a basis for detailed computational studies of semi-crystalline cross-linked polymer systems. [Display omitted] •Molecular simulation applied to the crystallization of cross-linked polymer melts.•Increase in cross-link density causes crystallization to slow down and decrease.•Cross-links are rejected into the amorphous inter-crystalline phase.•Amorphous phase is characterized by geometric distribution of free segment lengths.
ISSN:0032-3861
1873-2291
DOI:10.1016/j.polymer.2019.03.040