Study of permanent shear thinning of VM polymer solutions
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Published version
Author(s)
Marx, N
Ponjavic, A
Taylor, RI
Spikes, HA
Type
Journal Article
Abstract
The ultrashear viscometer (USV) has been adapted and employed to investigate the permanent shear thinning of polystyrene solutions in a series of phthalate ester base fluids. The permanent shear stability index based on viscosities measured at 106 s−1, PSSI(106), has been found to be a convenient way to express the magnitude of permanent shear thinning. When comparing permanent shear thinning at various shear rates in the USV, it is very important to take account of the different times of shear that are present at different shear rates. The PSSI(106) value divided by the total time of shear is then a useful way of quantifying and comparing permanent shear thinning rates. Tests using polystyrene in different viscosity base fluids have shown that this rate of permanent shear thinning depends on shear stress and not shear rate and varies linearly with polymer concentration. The rate of permanent shear thinning also varies exponentially with shear stress, suggestive of a stress-promoted polymer breakdown process. By using a small volume of test fluid in the USV and solvent extraction after a test, it has proved possible to obtain molecular weight distributions of polymer after shear using gel permeation chromatography (GPC). This indicates that the polymer breakdown process is different at low and high polymer concentrations, with molecule fragmentation at low polymer concentration but mid-chain scission at high concentration. A key feature of the USV is that, unlike other methods currently used to measure permanent shear thinning behaviour of engine oils, it subjects the test fluid to well-defined, controllable high shear conditions. Coupled with the use of GPC, this makes it possible for the first time to relate quantitatively the permanent shear thinning of engine oils to shear conditions and to polymer degradation response.
Date Issued
2017-07-07
Date Acceptance
2017-06-27
ISSN
1023-8883
Publisher
Springer Verlag
Journal / Book Title
Tribology Letters
Volume
65
Issue
3
Copyright Statement
© The Author(s) 2017. Open Access
This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
Identifier
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000405488400032&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Subjects
Science & Technology
Technology
Engineering, Chemical
Engineering, Mechanical
Engineering
Viscosity modifier (VM)
High shear rate
PSSI
Polymer degradation
Permanent shear thinning
Gel permeation chromatography
USV
MECHANICAL DEGRADATION
LINEAR MACROMOLECULES
SONIC DEGRADATION
DILUTE-SOLUTIONS
LAMINAR-FLOW
LUBRICANTS
POLYISOBUTENE
STABILITY
SCISSION
0912 Materials Engineering
0913 Mechanical Engineering
Mechanical Engineering & Transports
Publication Status
Published
OA Location
http://rdcu.be/t1pQ
Article Number
ARTN 106