Chemical and physical adsorption of polymers containing thiophosphate, amino, or polysiloxane groups at the oil/metal interface under extreme pressure

Abstract

Thiophosphate-and amino-containing polymers-poly[diethyl 2-(methacryloyloxy) ethyl phosphate-stearyl acrylate] (PPS) and poly(2-dimethylaminoethylacrylate-stearyl acrylate) (PNS)-were synthesized, and their characteristics at an oil/ metal interface under a high load and rotary velocity were investigated by the measurement of the temperature of the oil, the frictional coefficient, and the electrical contact resistance between the two metal surfaces. The experimental results indicated that PNS most effectively limited the increase of the oil temperature and the frictional coefficient at low temperatures. However, PNS reduced the oil temperature and frictional coefficient less effectively than the base oil at high temperatures, whereas PPS most effectively reduced the oil temperature and frictional coefficient and increased the electrical resistance at high temperatures. Moreover, the adsorption layers of PPS could be directly observed with scanning electron microscopy (SEM). These adsorption layers were analyzed by energy-dispersible spectrometry to determine the phosphorus content and by electron spectroscopy for chemical analysis to demonstrate the existence of ferric or ferrous ions of sulfide or sulfate. The results of this study suggested that the adsorption layer of the thiophosphate-containing polymer resulted in chemisorption by a reaction of the thiophosphate group on a metal surface. In contrast, an aminocontaining polymer was physically adsorbed onto a metal surface at low temperature, although no adsorption layer was observed at a high temperature with SEM.

Hyperbranched‐polyethyleneiminated functional polymers. III. Synthesizing thiophosphate‐containing pseudodendritic poly‐ethyleneiminated polyoxypropylenediamine and its behavior at an oil/metal interface under extreme pressure

“…Figures 4 and 5 clearly show that thiophosphate‐containing pseudodendritic polymers D400(EI) x P yield a lower increase in the oil temperature and yield a frictional coefficient of less than that of base oil and D400(EI) 8 . As stated in previous research,11 this result follows from the chemical adsorption of thiophosphate groups on a metal surface, which can reduce the frictional coefficient and oil temperature. Additionally, these results imply that the lowest oil temperature and frictional coefficient of the metal surfaces resulted from the presence of the most thiophosphate groups in D400(EI) 8 P.…”

“…In the authors' previous studies, thiophosphate‐ and amino‐containing polymers have been used as EP additives to form thick layers of polymer chains, rather than a thin molecular film, on a metal surface 8–11. The results show that an amino group in polymers physically adsorb onto a metal surface at low temperature and a thiophosphate‐containing group chemically reacts with the metal surface at high temperature.…”

Bifunctional hairy silica nanoparticles as high-performance additives for lubricant

“…3 , larger ratio of DETAS on the nanoparticle surface resulted in better tribological performance of the BHSNs at the optimal concentration (1 wt%). This result is due to amino functional groups that enhance the physical and chemical adsorption of nanoparticles onto the metal surface 36 37 . When more nanoparticles are adsorbed, the metal surface is more effectively protected by the BHSNs; consequently, the anti-wear and friction reduction properties of HSNs are improved.…”

Effect of solvent quality on kinetics of tethered layer formation

“…In the grafting to approach, previously prepared polymer chains are attached to the surface by means of anchor blocks or end‐functional groups 3–5. In the grafting from approach, an initiator is first attached to the solid surface, after which a solution of monomer is brought into contact with the solid surface; the polymer chains then grow from the initiator sites to form the tethered layer 6–11. The grafting from approach tends to yield denser polymer layers, in terms of chains/nm 2 , than does the grafting to approach.…”