All-atomic and coarse-grained molecular dynamics investigation of deformation in semi-crystalline lamellar polyethylene

Research output: Contribution to journalArticle

Abstract

In the present work we have performed classical molecular dynamics modelling to investigate the effects of different types of force-fields on the stress-strain and yielding behaviours in semi-crystalline lamellar stacked linear polyethylene. To this end, specifically the all-atomic optimized potential for liquid simulations (OPLS-AA) and the coarse-grained united-atom (UA) force-fields are used to simulate the yielding and tensile behaviour for the lamellar separation mode. Despite that the considered samples and their topologies are identical for both approaches, the results show that they predict widely different stress-strain and yielding behaviours. For all UA simulations we obtain oscillating stress-strain curves accompanied by repetitive chain transport to the amorphous region, along with substantial chain slip and crystal reorientation. For the OPLS-AA modelling primarily cavitation formation is observed, with small amounts of chain slip to reorient the crystal such that the chains align in the tensile direction. This force-field dependence is rooted in the lack of explicit H-H and C-H repulsion in the UA approach, which gives rise to underestimated ideal critical resolved shear stress. The computed critical resolved shear stress for the OPLS-AA approach is in good agreement with density functional theory calculations and the yielding mechanisms resemble those of the lamellar separation mode. The disparate energy and shear stress barriers for chain slip of the different models can be interpreted as differently predicted intrinsic activation rates for the mechanism, which ultimately are responsible for the observed diverse responses of the two modelling approaches.

Details

Authors
  • Pär Olsson
  • Pieter in 't Veld
  • Eskil Andreasson
  • Erik Bergvall
  • Elin Persson Jutemar
  • Viktor Petersson
  • Gregory Rutledge
  • Martin Kroon
Organisations
External organisations
  • BASF
  • Tetra Pak AB
  • Massachusetts Institute of Technology
  • Malmö University
  • Blekinge Institute of Technology
  • Linnaeus University
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Textile, Rubber and Polymeric Materials
Original languageEnglish
Pages (from-to)305-316
Number of pages12
JournalPolymer
Volume153
Publication statusPublished - 2018 Sep 26
Publication categoryResearch
Peer-reviewedYes