Synthetic lubricants oxidative stability

Organophosphorus Derivatives. Neopentyl glycol treated with pyridine and phosphorus trichloride in anhydrous dioxane yields the cycHc hydrogen phosphite, 5,5-dimethyl-l,3-dioxaphosphorinane 2-oxide (2) (32,33). Compounds of this type maybe useful as flameproofing plasticizers, stabilizers, synthetic lubricants, oil additives, pesticides, or intermediates for the preparation of other organophosphoms compounds (see Flame retardants Phosphorus compounds). 

Polypheny I Ethers. Both alkyl-substituted and iinsubxtiinlcd polypheny ethers are included in this class of synthetic lubricants. General preparation involves the (.llhiian ether synthesis. The unsubstituted polyphenyl ethers have outstanding thermal, oxidative and radiation resistance, however, poor low-temperature characteristics arc a major drawback. Alkyl substitution improves low-temperature viscosity, but detracts from stability. Most lubricant uses are developmental in nature and involve aircrali and aerospace applications. 

Lubricants are formulated products composed of a base stock, which is either a mineral or synthetic oil, and various specialty additives designed for specific performance needs. Additive levels in lubricants range from 1 to 25% depending on the application. Synthetic base stocks are oligomers of small molecules, synthesized to a defined molecular weight. Important performance indicators include viscosity index which measures the viscosity index behavior over a temperature range, oxidative stability, and pour point. The performance of synthetic and mineral oils (Morse, 1998 Shubkin, 1993) is summarized in Table 2.7. 

It is not sufficient merely to have such material on the libraiy shelves it must also be carefully indexed. All new books and pamphlets received are examined carefully for information that would not ordinarily be expected in such publications. In The Chemistry of the Non-Benzenoid Hydrocarbons (1922) by B. T. Brooks, for example, there are references to naphthenic acids, production of fatty acids by wax oxidation, and synthetic lubricating oils. In Volume VI of Colloid Chemistry (1946) edited by Jerome Alexander, there are chapters on the Geiger-Miiller x-ray spectrometer, electron microscopy, catalysis and its industrial applications, soil stabilization, polythene, and potential nuclear energy. Such information is typed on 3 X 5 cards on some books as many as forty or fifty cards may be required. In this way an extremely useful file of information has been built up that might otherwise be overlooked as valuable data sometimes appear in unexpected places. 

ILs viscosity iuCTeased when the chain lengA of the side chain increases, the side chain is composed of fluoride or an imidazole ring in position 2 methylation, or there is increased cation symmetry. Generally, when the cation is composed of the thermally stable imidazolium ion, the anion determines the thermal stability of the entire IL, increasing in the order TfjN >BF >PF ">halogen ions. Minami et al. [18] studied thermo-oxidative stability and volatility of ILs and found that ILs have greater thermal stability than conventional synthetic lubricants. It was also found that the stability of an ILs depends on the structures of both the anion and the cation. For example, the stability of 1, 3-dialkyl-imidazoUum is more stable than quaternary ammonium. 

The wide temperature performance range for PAO-based lubricants together with their excellent physical, chemical and thermo-oxidative stabilities has increased the use of PAOs in a wide variety of applications. Traditional application areas such as aerospace, transmissions and hydraulic systems continue to require the lubricant performance benefits of PAOs. In addition, the stresses of both increased performance and longer lifetimes placed on automotive and marine lubricants have increased growth in the use of PAO-based synthetic lubricants in these applications. 

Still there are efforts to improve the performance of natural mineral oil-based lubricants by the synthesis of oligomeric hydrocarbons, which has been the subject of important research and development in the petroleum industry for many years and has led to commercialization of a number of synthetic lubricants. These materials are based on the oligomerization of a-olefins such as C6-C20 olefins. Industrial research effort on synthetic lubricants has generally focused on improved viscosity index, thermal and oxidative stability, and a pour point equal to or better than that of the corresponding mineral oil lubricants. 

PAO blended with mineral oil are also used in many partial synthetic lubricant formulations. In this case, PAO is used as a blending stock to improve the volatility, high or low-temperature viscosity, oxidative stability, etc. of the mineral oil blend. 

Phthalic anhydride or trimellitic anhydride are converted into esters by reactions with alcohols as shown in Figure 8. Phthalic anhydride is produced cheaply and in large volume from oxidation of ortho-xylene. The largest use of phthalate esters is in the plasticizer market. Only a small fraction of its production is consumed by the synthetic lubricants market. Phthalate esters generally have superior hydrolytic stability than adipic esters because the ortho di-ester groups are electronically less available and sterically more hindered. However, they have lower Vis, 50-70, because of their high polarity and the presence of branched alcohol chains. They are used in special industrial oil applications where VI is not a critical parameter. Trimellitate esters are specialty products and relatively expensive. They are of high viscosity and usually are more resistant to oxidation than adipic esters. 

Applications - Esters, both dibasic and polyol esters, are used as co-base stocks with PAO or other hydrocarbon base stocks in synthetic automotive engine lubricants and industrial lubricants. Polyol esters are used in aircraft tuibine oils due to their excellent thermal and oxidative stabilities, good lubricity, high VI and excellent low temperature properties (<-40°C). Esters are also used in synthetic compressor oils for ozone-ffiendly refngeration units. Because of their high biodegradability and low toxicity, esters are often the base oils of choice for many environmentally-aware... 

Electrolytic Tinplate. Much of the tin mill product is made into electrolytic tinplate (ETP). A schematic of an ETP cross section is given in Figure 1. The steel strip is cleaned electrolytically in an alkaline bath to remove rolling lubricants and dirt, pickled in dilute mineral acid, usually with electric current applied to remove oxides, and plated with tin. It is then passed through a melting tower to melt and reflow the tin coating to form the shiny tin surface and the tin-iron alloy layer, chemically treated to stabilize the surface to prevent growth of tin oxide, and lubricated with a thin layer of synthetic oil. 

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