Molecular dynamics simulations of crystal nucleation in entangled polymer melts under start-up shear conditions

Anwar, Muhammad; Graham, Richard S.

Abstract

Understanding the flow induced crystallisation (FIC) process is necessary due to its technological relevance to polymer processing. Polymer crystallisation controls the morphology of semi-crystalline polymers and hence the properties of the end product. We perform molecular dynamics simulations of polymer melts consisting of sufficiently entangled linear chains under shear flow. We determine the Rouse relaxation time (τ R) for linear polymer chains using an established rheological model at different temperatures and fit the simulation data with the Arrhenius and Williams-Landel-Ferry (WLF) equations. We simulate the crystallisation induction times for different values of the Rouse Weissenberg number (W iR = ˙ γτ R) at different temperatures. We observe that the level of strain and stretch required to induce crystallisation increases with temperature. We find that the induction times follow a power law in shear rate and observe a more pronounced effect of flow rate for higher temperatures than at lower temperatures. Moreover, we determine that nucleation events occur relatively early in the shear transient and at a stretch value that is smaller than its steady state value. We also report the values of strain at which the occurrence of a nucleation event is most likely to happen.

Citation

Anwar, M., & Graham, R. S. (2019). Molecular dynamics simulations of crystal nucleation in entangled polymer melts under start-up shear conditions. Journal of Rheology, 150(8), Article 084905. https://doi.org/10.1063/1.5082244

• Journal Article Type: Article
• Acceptance Date: Feb 7, 2019
• Online Publication Date: Feb 27, 2019
• Publication Date: Feb 27, 2019
• Deposit Date: Feb 12, 2019
• Publicly Available Date: Feb 12, 2019
• Journal: The Journal of Chemical Physics
• Print ISSN: 0148-6055
• Electronic ISSN: 1520-8516
• Publisher: American Institute of Physics
• Peer Reviewed: Peer Reviewed
• Volume: 150
• Issue: 8
• Article Number: 084905
• DOI: https://doi.org/10.1063/1.5082244
• Keywords: Physical and Theoretical Chemistry; General Physics and Astronomy
• Public URL: https://nottingham-repository.worktribe.com/output/1541405
• Publisher URL: https://aip.scitation.org/doi/10.1063/1.5082244
• Additional Information: The following article has been accepted by Journal of Rheology. After it is published, it will be found at 10.1063/1.5082244
• Contract Date: Feb 12, 2019