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Substituent effects on the mechanochemical response of zinc dialkyldithiophosphate

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Title: Substituent effects on the mechanochemical response of zinc dialkyldithiophosphate
Authors: Zhang, J
Ewen, J
Spikes, H
Item Type: Journal Article
Abstract: Mechanochemistry is known to play a key role in the function of some lubricant additives, such as the tribofilm growth of zinc dialkyldithiophosphate (ZDDP). This raises the intriguing possibility of tailoring the mechanochemical response of additives by modifying their alkyl substituents. Here, we study the tribofilm formation rate of ZDDPs containing several different alkyl groups on steel surfaces from a high-friction base oil. We use macroscale tribometer experiments under full-film elastohydrodynamic lubrication conditions to enable careful control of the temperature and stress during tribofilm growth. We show how the chain length and the presence of branches or bulky cycloaliphatic groups can lead to large differences in the temperature- and stress-dependencies of the tribofilm formation rate, which can be explained through variations in packing density, steric hindrance, and stress transmission efficiency. Our rate data are successfully fitted using the Bell model; a simple modification of the Arrhenius equation that is commonly employed to model the kinetics of mechanochemical processes. Using this model, we observe large differences in the activation energy, pre-exponential factor, and activation volume for the various ZDDPs. Our findings show how structure–performance relationships can be identified for lubricant additives, which may be useful to optimise their molecular structure.
Issue Date: 30-May-2022
Date of Acceptance: 27-May-2022
URI: http://hdl.handle.net/10044/1/97559
DOI: 10.1039/D2ME00049K
ISSN: 2058-9689
Publisher: Royal Society of Chemistry
Start Page: 1045
End Page: 1055
Journal / Book Title: Molecular Systems Design & Engineering
Volume: 7
Issue: 9
Copyright Statement: © The Royal Society of Chemistry and IChemE 2022. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
Sponsor/Funder: Royal Academy Of Engineering
Engineering & Physical Science Research Council (EPSRC)
Funder's Grant Number: RF\201920\19\269
EP/P030211/1
Keywords: Science & Technology
Physical Sciences
Technology
Chemistry, Physical
Engineering, Chemical
Nanoscience & Nanotechnology
Materials Science, Multidisciplinary
Chemistry
Engineering
Science & Technology - Other Topics
Materials Science
SELF-ASSEMBLED MONOLAYERS
CHAIN-LENGTH
ELASTOHYDRODYNAMIC LUBRICATION
THERMAL-DECOMPOSITION
STEEL SURFACES
FILM THICKNESS
SAM MODEL
IN-SITU
MECHANISMS
MOLECULES
Publication Status: Published
Online Publication Date: 2022-05-30
Appears in Collections:Mechanical Engineering
Faculty of Natural Sciences
Faculty of Engineering



This item is licensed under a Creative Commons License Creative Commons