Li Weimin, Kumara Chanaka, Luo Huimin, Meyer Harry M, He Xin, Ngo Dien, Kim Seong H, Qu Jun
State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, Gansu 730000, China.
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.
ACS Appl Mater Interfaces. 2020 Apr 8;12(14):17077-17090. doi: 10.1021/acsami.0c00980. Epub 2020 Mar 31.
Interactions among antiwear additives (AWs), friction modifiers (FMs), and dispersant in a lubricating oil are critical for tribological performance. This study investigates compatibilities of three oil-soluble ionic liquids (ILs, candidate AWs) with an FM, molybdenum dithiocarbamate (MoDTC), and a dispersant, polyisobutene succinimide (PIBSI) under boundary lubrication. Either synergistic or antagonistic effects were observed depending on the IL's chemistry. Adding an aprotic phosphonium-alkylphosphate or phosphonium-alkylphosphinate IL into the oil containing MoDTC and PIBSI had detrimental impact on the friction and wear behavior. PIBSI was found to preferably interact/react with the aprotic IL to lose its ability of suspending MoDTC and to partially consume or even deplete the IL. In contrast, a protic ammonium-alkylphosphate IL seemed to be able to coexist with PIBSI and work synergistically with MoDTC, yielding a sustainable, ultralow boundary friction. A three-stage tribochemical process is proposed to explain how this IL + MoDTC pair interacts with the contact surface to form a chemically reacted, wear-protective tribofilm supporting a physically adsorbed, friction-reducing film on top. This study provides fundamental insights of the compatibilities among three common lubricant components, antiwear, friction modifier, and dispersant, which can be used to guide future lubricant development.
抗磨添加剂（AWs）、摩擦改进剂（FMs）和润滑油中的分散剂之间的相互作用对摩擦学性能至关重要。本研究调查了三种油溶性离子液体（ILs，候选抗磨添加剂）与一种摩擦改进剂二硫代氨基甲酸钼（MoDTC）和一种分散剂聚异丁烯琥珀酰亚胺（PIBSI）在边界润滑条件下的相容性。根据离子液体的化学性质，观察到了协同或拮抗作用。向含有MoDTC和PIBSI的油中添加非质子型磷酸鏻 - 烷基磷酸盐或磷酸鏻 - 烷基次膦酸盐离子液体对摩擦和磨损行为有不利影响。发现PIBSI优先与非质子型离子液体相互作用/反应，从而失去悬浮MoDTC的能力，并部分消耗甚至耗尽离子液体。相比之下，质子型磷酸铵 - 烷基磷酸盐离子液体似乎能够与PIBSI共存，并与MoDTC协同作用，产生可持续的超低边界摩擦。提出了一个三阶段摩擦化学过程来解释这种离子液体 + MoDTC组合如何与接触表面相互作用，形成一个化学反应的、耐磨的摩擦膜，在其顶部支撑一个物理吸附的、减摩的膜。本研究提供了对三种常见润滑剂成分（抗磨剂、摩擦改进剂和分散剂）之间相容性的基本见解，可用于指导未来的润滑剂开发。
