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Chemicals from Non-hydrocarbons
Published in James G. Speight, Handbook of Petrochemical Processes, 2019
Other uses range from dusting powder for roses to rubber vulcanization to sulfur asphalt pavements. Flower sulfur is used in match production and in certain pharmaceuticals. Sulfur is also an additive in high-pressure lubricants. Sulfur can replace 30%–50% w/w of the asphalt in the blends used for road construction. Road surfaces made from asphalt-sulfur blends have nearly double the strength of conventional pavement, and it has been claimed that such roads are more resistant to climatic conditions. The impregnation of concrete with molten sulfur is another potential large sulfur use. Concretes impregnated with sulfur have better tensile strength and corrosion resistance than conventional concretes. Sulfur is also used to produce phosphorous pentasulfide, a precursor for zinc dithiophosphate derivative used as corrosion inhibitors.
Biocoatings and additives as promising candidates for ultralow friction systems
Published in Green Chemistry Letters and Reviews, 2021
Marcia Gabriely A. da Cruz, Tetyana M. Budnyak, Bruno V. M. Rodrigues, Serhiy Budnyk, Adam Slabon
Organophosphates (OP) are a well-known class of additives used in turbine oil lubricants. Despite the efficiency that organophosphorus compounds add to the lubrication systems, they represent a serious problem due to the generation of phosphorus emission and the toxicity of the degradation products (15). We have shown that in the case of lubricants containing functional additives, e.g. zinc dithiophosphate (ZDDP), detergents, dispersants, and antioxidants for engine and gear lubricants, the generated soot matrix particles contain 3–5 nm ZnO:P,S nanoparticles (16). Part of the issue caused by the use of OPs can be managed by substitution with thiazoles without efficiency losses. Another friction modifier widely applied in engine lubricants is the molybdenum di-thiocarbamate (Mo-DTC), which produces a tribofilm with MoS2 sheets that lead to low friction (17). However, this organic lubricant additive is a source of harmful emissions due to its toxicity (18).
Improving Hypoid Gear Oil Pitting Performance through Friction Reduction
Published in Tribology Transactions, 2020
Jens E. Johansson, Mark T. Devlin, Jeffrey M. Guevremont, Braham Prakash
The exact mechanism by which the AW/EP tribofilms affect thin-film friction is unclear. Previous studies have shown that the tribofilms formed by various AW/EP additives display different characteristics and morphologies (Topolovec-Miklozic, et al. (57); Najman, et al. (58)). For example, zinc dithiophosphate (ZDDP) AW additives are often found to have relatively high friction, which is often attributed to their unevenly distributed tribofilms (Taylor, et al. (8); Kapadia, et al. (9); Bennett (59)). Compared to ZDDP, ashless phosphorus-based AW additives form smoother and relatively thin films (Devlin, et al. (10)), and ball-on-disc tests have also shown that they tend to result in lower friction than those formed by ZDDP (Ribeaud (11)). However, a more recent study showed that ZDDP tribofilms can produce high friction even when the films formed are quite smooth (Taylor and Spikes (7)), implying that the exact mechanisms are not yet completely understood.
Tribological Behaviors of W/Mo Films under Lubrication of Zinc Dithiophosphates—Understanding Their Roles in Tribochemical Reactions
Published in Tribology Transactions, 2019
Xingliang Li, Wen Yue, Zhiqiang Fu, Haipeng Huang, Chengbiao Wang, Jiajun Liu
A lower viscosity lubricant and more effective additives are required to improve engine efficiency and durability in future engines (Zhou, et al. (7)). Ionic liquids (Qu, et al. (8); Berman, et al. (9)), graphene (Yadgarow, et al. (10)), and inorganic fullerene-like WS2/MoS2 nanoparticles (Tang and Li (11)) have been explored as potential lubricant additives in engine oils. However, zinc dithiophosphate (ZDDP) with a chemical formula of Zn[S2P(OR)2]2, where R is an alkyl or aryl group, is the most common antiwear additive and antioxidant used in commercially fully formulated engine oil. It has proved to be the most effective antiwear additive and cannot be fully replaced (Spikes (12); Nicholls, et al. (13)). Tribochemical reactions of ZDDP have been extensively published in the last decade (Mosey (14); Onodera, et al. (15)). Unfortunately, a ZDDP tribofilm formed on modified surfaces or coatings is not as fully understood as that on iron-based materials.