New Boron-containing Benzothiazole Ester Derivatives As Lubricant Additive Synthesis And Tribological Properties Of Study

With the accelerative development of modern industry, multi-functional environment-friendly additives containing boron is the future direction in the field of the lubricating oil. And its comprehensive performance will be gotten more and more attention. Rapeseed oil, in general, has excellent properties such as high viscosity index, high lubricity, high biodegradability and low toxicity with regard to their use as base oils for lubricants, in which additives are able to improve the load-carrying capacities and anti-wear and friction-reducing properties, is a kind of the most competitive green oils.In this paper, from rational molecular design, six kinds of additives have been designed and synthesized by using 2-mercaptobenzothiazole compound as material. Their main chemical structures were characterized by using IR, EA. Their tribological properties, sensitivity and compatibility among additives and base oils were studied by a series of texts. Specific studies are as follows:(1) Six kinds of additives were designed and synthesized. Their main chemical structures were characterized by using IR, EA. The results show that the synthesized compounds are consistent with the molecular design.(2) The physico-chemical properties of additives, such as oil solubility, thermal stability, anticorrosive property and viscosity, were studied. As a results, benzothiazole easter compounds containing boron as rapeseed oil additives exhibited good oil-soluble, anticorrosive properties and high thermal stability.(3) Their tribological performance as additives in rapeseed oil was investigated using a MRS-10A four-ball testing machine. And the relation between the molecular structures and tribological properties were discussed. The results show that the tribological properties of boron-containing benzothiazole easter compounds vary with the molecular structure, the rank of tribological properties is BNS-2>BNS-1, DOEB>DSOEB and LBNS>LBN.(4) The chemical states of some typical elements on the worn surfaces of the lower steel balls lubricated by 1.0%BNS-2,1.0%DOEB and 1.0%LBNS respectively were analyzed with X-ray photoelectron spectrometer (XPS). XPS analyses of the worn surface show base oil and the additive are competing against each other in adsorbing to form the lubrication oil film on the steel surface in the initial stage of the friction. As the test time goes on, the metal surface temperature is increased, so a complicated frictional chemical reaction takes place between the additive and the metal surface or additives is decomposed to generate some N-containing, S-containing organic compounds adsorbed on the metal surface. It is the adsorption film and the chemical reaction film that play an important role in improving anti-wear and friction-reducing properties.(5) The worn surface of the lower steel ball lubricated by 1.0% LBNS in rapeseed oil was etched by Ar ion-beam for 5 min. It was found that there were carbon, oxygen and iron elements in the metal sub-surface. The absorption peaks of carbon and oxygen elements became weaker and that of iron element increased, which indicated that iron was exposed after the surface film gradually removed. But there were still iron oxides. Little boron, sulfur and nitrogen elements could be found in the sub-surface, indicating that additives mainly adsorbed on the steel metal surface.