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Molecular simulation of gas solubility in nitrile butadiene rubber

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Title: Molecular simulation of gas solubility in nitrile butadiene rubber
Authors: Khawaja, M
Sutton, AP
Mostofi, AA
Item Type: Journal Article
Abstract: Molecular simulation is used to compute the solubility of small gases in nitrile bu- tadiene rubber (NBR) with a Widom particle-insertion technique biased by local free volume. The convergence of the method is examined as a function of the number of snapshots upon which the insertions are performed and the number of insertions per snapshot, and is compared to the convergence of the unbiased Widom insertion technique. The effect of varying the definition of the local free volume is also investi- gated. The acrylonitrile content of the polymer is altered to examine its influence on the solubility of helium, CO 2 and H 2 O, and the solubilities of polar gases are found to be enhanced relative to nonpolar gases, in qualitative agreement with experiment. To probe this phenomenon further, the solubilities are decomposed into contributions from neighbourhoods of different atoms, using a Voronoi cell construction, and a strong bias is found for CO 2 and H 2 O in particular to be situated near nitrogen sites in the elas- tomer. Temperature is shown to suppress the solubility of CO 2 and H 2 O, but increase that of helium. Increasing pressure is found to suppress the solubility of all gases, but at different rates according to a balance between their molecular size and electrostatic interaction with the polymer. These results are relevant to the use of NBR seals at elevated temperatures and pressures, such as in oil and gas wells.
Issue Date: 6-Dec-2016
Date of Acceptance: 6-Dec-2016
URI: http://hdl.handle.net/10044/1/43084
DOI: https://dx.doi.org/10.1021/acs.jpcb.6b09690
ISSN: 1520-6106
Publisher: American Chemical Society
Start Page: 287
End Page: 297
Journal / Book Title: Journal of Physical Chemistry B
Volume: 121
Issue: 1
Copyright Statement: © 2016 American Chemical Society. ACS AuthorChoice - This is an open access article published under a Creative Commons Attribution (CC-BY) License, which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited.
Sponsor/Funder: Baker Hughes Limited
Engineering and Physical Sciences Research Council
Funder's Grant Number: Agreement No: 6-54131
EP/G036888/1
Keywords: 03 Chemical Sciences
09 Engineering
02 Physical Sciences
Publication Status: Published
Open Access location: http://dx.doi.org/10.1021/acs.jpcb.6b09690
Appears in Collections:Faculty of Engineering
Condensed Matter Theory
Materials
Physics
Faculty of Natural Sciences



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