Effects of conformational entropy on antiwear performances of organic friction modifiers

Influence of Adsorption Characteristics of Surfactants Sodium Dodecyl Sulfate and Aerosol–OT on Dynamic Process of Water-Based Lubrication

“…The statistical results of the final adsorption amount of different concentrations of SDS were larger than that of the AOT solutions at all concentrations (Figure 8b), and the dissipations were all less than 2.0 × 10 −6 . The result was reasonable, because the molecular structure of SDS is a single straight chain, while that of AOT is a double-branched chain, such that SDS can be arranged more densely than AOT on the Al 2 O 3 sensor of QCM [7,44]. The peak value in the adsorbed amount curve of 15 mM SDS (Figure 8a) was due to the fact that SDS reached the surface of the Al 2 O 3 sensor in the form of micelles and then underwent a transition of arrangement structure upon adsorption, and the difference in the arrangement structures of different concentrations of SDS solutions on the surface was probably the reason for their different adsorption amount.…”

“…There are two possible reasons. Firstly, the boundary film of SDS was denser (Figure 8), which meant that it could achieve a better anti-friction effect [44]. Secondly, some parts of the contact zones were very limited in space, with only one or a few molecular diameters.…”

Effect of functional groups on tribological properties of lubricants and mechanism investigation

“…Energy consumption owing to friction accounts for 23%, approximately 119 EJ, of global energy consumption [1,2]. In present industrialized nations, financial wastage brought by friction and wear is as high as about 6% of GDP [1,3]. In order to protect the environment and reduce economic loss, frictional energy losses and wear should be minimized [4][5][6], which requires higher energy efficiency of mechanical system [7,8].…”

“…As an important class of lubricant additives, OFMs are typical amphiphilic surfactant molecules with non-polar aliphatic tail groups and polar head groups [3,8,10,12,14,15]. The polar head groups can adsorb on the substrate surface, and long aliphatic tail groups align outward into the lubricating oil, forming close-packed self-assembled monolayers [14,[16][17][18][19][20][21][22].…”

“…The tribological properties of OFMs are related tightly to their structures, including the reaction activity of polar head groups, molecular chain length, and unsaturation degrees of OFMs. Ouyang et al [3] found that glyceryl monostearate (GMS) and glyceryl monoelaidate (GME) exhibited better tribological performances compared to glyceryl monooleate (GMO). During film formation, the GMO stretched out horizontally due to the existence of its cis double bond, resulting in more loss of conformational entropy, the lower surface coverage of tribofilm, and the worse lubricating properties.…”