Rheological and structural studies of linear polyethylene melts under planar elongational flow using nonequilibrium molecular dynamics simulations

The Journal of Chemical Physics
Chunggi BaigV A Harmandaris

Abstract

We present various rheological and structural properties of three polyethylene liquids, C50H102, C78H158, and C128H258, using nonequilibrium molecular dynamics simulations of planar elongational flow. All three melts display tension-thinning behavior of both elongational viscosities, eta1 and eta2. This tension thinning appears to follow the power law with respect to the elongation rate, i.e., eta approximately epsilon(b), where the exponent b is shown to be approximately -0.4 for eta1 and eta2. More specifically, b of eta1 is shown to be slightly larger than that of eta2 and to increase in magnitude with the chain length, while b of eta2 appeared to be independent of the chain length. We also investigated separately the contribution of each mode to the two elongational viscosities. For all three liquids, the intermolecular Lennard-Jones (LJ), intramolecular LJ, and bond-stretching modes make positive contributions to both eta1 and eta2, while the bond-torsional and bond-bending modes make negative contributions to both eta1 and eta2. The contribution of each of the five modes decreases in magnitude with increasing elongation rate. The hydrostatic pressure shows a clear minimum at a certain elongation rate for each liquid, and ...Continue Reading

Citations

Apr 10, 2014·The Journal of Chemical Physics·Chau Tran, Vibha Kalra
Jan 5, 2019·Physical Review Letters·Mohammad H Nafar SefiddashtiBamin Khomami
Jan 9, 2017·Polymers·Ali GooneieClemens Holzer
Dec 19, 2009·The Journal of Physical Chemistry. B·Qifei WangJ Brock Thomas
Jun 30, 2019·The Journal of Physical Chemistry. B·Konstantinos D PapavasileiouIoannis G Economou

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