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

Anwar, Muhammad; Graham, Richard S.

Authors

Muhammad Anwar

RICHARD GRAHAM richard.graham@nottingham.ac.uk
Professor of Applied Mathematics



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.

Journal Article Type Article
Publication Date Feb 27, 2019
Journal The Journal of Chemical Physics
Print ISSN 0148-6055
Electronic ISSN 1089-7690
Publisher AIP Publishing
Peer Reviewed Peer Reviewed
Volume 150
Issue 8
Article Number 084905
APA6 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), https://doi.org/10.1063/1.5082244
DOI https://doi.org/10.1063/1.5082244
Keywords Physical and Theoretical Chemistry; General Physics and Astronomy
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

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