Crystallinity of polyethylene in uni-axial extensional flow

Sara Lindeblad Wingstrand, Martin van Drongelen, Kell Mortensen, Richard S. Graham, Qian Huang, Bo Shen, Julie A. Kornfield, Ole Hassager

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Abstract

Flow history of polymer melts in processing greatly influences the crystallinity and hence the solid properties of the final material. A wide range
of polymer processes involve extensional flows e.g. fiber spinning, blow moulding etc. However, due to instrumental difficulties, experimental
studies on polymer crystallization in controlled uniaxial extension are quite rare compared to studies of crystallization in shear. Inherently
uniaxial extensional flows are strong and simple relative to shear flows, in the sense that chain stretch is easily obtained and that the molecules
experience no tumbling, hence much can be learned from studying polymers in extension. Recent advances in filament stretching rheometry
now enable the performance of controlled uniaxial stretching of polymeric liquids even to high Hencky strains [1]. In addition the instrument
allows for quenching at specific strains such that crystallization from a stretched state can take place. In this work we explore this feature in the
attempt to link the nonlinear extensional rheology to the final morphology. We investigate polyethylenes (PE) of various chain architectures and
observe that, even for complex architectures like long chain branched PE, the final morphology is determined by the stress at quench. This can
be explained by realizing that nonlinearity in stress arises from changes in molecular configuration such as chain stretch. Hence the nonlinear
stress response reflects the molecular configuration during stretching determining the final morphology [2].
Original languageEnglish
Publication date2017
Number of pages1
Publication statusPublished - 2017
EventThe Annual European Rheology Conference (AERC2017) - Copenhagen, Denmark
Duration: 3 Apr 20176 Apr 2017

Conference

ConferenceThe Annual European Rheology Conference (AERC2017)
CountryDenmark
CityCopenhagen
Period03/04/201706/04/2017

Cite this

Wingstrand, S. L., van Drongelen, M., Mortensen, K., S. Graham, R., Huang, Q., Shen, B., Kornfield, J. A., & Hassager, O. (2017). Crystallinity of polyethylene in uni-axial extensional flow. Abstract from The Annual European Rheology Conference (AERC2017), Copenhagen, Denmark.