Synthetic esters, lubricated

Fuels, Lubricants, and Transmission Fluids. Polyol esters of neopentanoic acid have been used as high vacuum pumping hquids that are stable in chemically aggressive environments (70). Esters such as 6- -ani1inophenoxy)hexy1 pivalate are used as antioxidants for synthetic ester lubricants (71). PivaUc anhydride [1538-75-6] has been claimed as an antiknock additive for gasoline (72). 

As described in Chapter 1, mineral oil base stocks are derived from crude oil and are complex mixtures of naturally occurring hydrocarbons. Synthetic ester lubricants, on the other hand, are prepared from man-made base stocks having uniform molecular structures giving well-defined properties which can be tailored to specific applications. 

Figure 14-1. Wear and partial elastohydrodynamic lubrication. (a) Synthetic ester lubricant. (b) Mineral oil lubricant. Data by Tallian et al. [2].

Of the numerous possibilities arising from the esterification of polycarboxylic acids by polyhydroxylic alcohols, fortunately only a few need be considered seriously from the viewpoint of utility as synthetic ester lubricants. Most of the esters that find application as lubricant fluids are products of the reaction of monohydroxylic alcohols and dicar-boxylic acids for example, the simple type structure shown below ... 

Boyde, S. Hydrolytic Stability of Synthetic Ester Lubricants, J. Synth. Lubr., 2000,16-4, 297. 

This test method provides a calculation procedure for converting data obtained by Test Method D 972, to apparent vapor pressures and molecular weights. It has been demonstrated to be applicable to petroleum based and synthetic ester lubricating oils, at temperatures of 395 to 535 K (250 to 500°F). However, its applicability to lubricating greases has not been established. 

Poly(a-olefins) or PAOs, polyol esters and diesters are now used in automotive and marine engine oils. To understand how an ester lubricates, it is important to consider its behavior in the different lubrication regimes, especially boundary lubrication when the properties of the bulk lubricant (e.g. viscosity) are of minor importance. The chemical properties of the lubricant responses under extreme conditions will become increasingly important. The polar ester will preferentially stick to the surface of metal when a small amount of ester is added to a low viscosity nonpolar fluid (PAO), (Randles, 1999 Spikes, 1999). When the two metal surfaces come closer together, the polar ester molecules stay in the contact zone. The use of fully synthetic engine oil formulations has produced some improvement in viscosity control and engine cleanliness in the piston and valve train areas over petroleum-based oils (Boehringer, 1975 Frame et ah, 1989 Kennedy, 1995 Lohuis and Harlow, 1985). 

Like amides, esters are common both in nature and in the chemical industry. Animal fats and vegetable oils are mixtures of esters, as are waxy materials such as beeswax and spermaceti. Plants often synthesize esters that give the characteristic tastes and odors to their fruits and flowers. In addition to making synthetic esters for flavors, odors, and lubricants, chemists have made synthetic polyesters such as Dacron polyester fiber used in clothing and Mylar polyester film used in magnetic recording tapes. 

Plexor [Rohm Haas], TM for synthetic lubricants and additives for petroleum oils. Most grades are diesters of dibasic acids some are polyesters or polyether alcohols. The ester lubricants have very low freezing points, high flash points, little change of viscosity with temperature. 

Jimenez AE, Bermudez MD (2008) Imidazolium ionic liquids as additives of the synthetic ester propylene glycol dioleate in aluminium-steel lubrication. Wear 265 787-798... 

To lubricate high and ultra-high vacuum pumps special lubricants with low vapour pressures at the working temperature are used, produced from naphthenic or paraffinic mineral oils by molecular distillation with good oxidative and thermal stability. Synthetic esters are another group of lubricants for vacuum pumps, the most widely used are di-n-butyl and di-n-octyl phthalates. 

Several classes of synthetic oils, such as phosphoric acid esters, polyglycols and silicones, are used as hydraulic lubricants. They are mostly used as fire-resistant lubricants, of importance for coal mines, steel mills and foundries, especially when hydraulic systems operate close to hot areas, e.g. furnaces. Polychlorinated biphenyls, PCBs, are the most fire resistant but are no longer used because of their high and persistent toxicity. Silicones have very poor lubricity and are very expensive, whereas polyglycols with high flash points do not fiilly meet more stringent fire-resistant requirements. At present, therefore, synthetic hydraulic lubricants are almost exclusively based on trialkyl or triaryl phosphates, or their mixtures, available with a wide range of viscosities and adequate low-temperature properties required for hydraulic lubricants. 

As the spectra in Fig. 16.6 indicate, a HATR cell results in a loss of signal sensitivity of about a factor of 20 when compared to a 100-p.m transmission cell. This signal loss hampers analysis of petroleum lubricants and prevents analysis of synthetic esters. 

Synthetic esters like polyol esters or neopentyl polyol esters are made from monobasic fatty acids and polyhedric alcohols with a neopentyl structure (see Figure 7.6). On these molecules, there are no hydrogen atoms on the beta carbon. This carbon is where thermal attack occurs on diesters and eliminating it improves the thermal stability of the molecule. Polyol esters have an increased number of ester groups versus diesters. This feature increases polarity, which will affect the lubricity of the oil at elevated temperatures and give it an advantage over PAOs. 

PEG-2 laurate SE PEG-2 oleate PEG-2 oleate SE PEG-2 stearate SE PPG-2 laurate PPG-2 oleate PPG-2 stearate antistat, scalp treatment Quatemium-51 Thenoyl methionate antistat, semi-synthetic metalworking lubricants Sorbitan tritallate antistat, setting lotions Octyl aery I am i de/acry I ates/buty I am i noethyl methacrylate copolymer PVM/MA copolymer, butyl ester Sodium polystyrene sulfonate antistat, shampoo... 

Crump [13] has analysed edible oils which had been contaminated or adulterated with mineral oil-containing lubricants and with the help of TLC was able to distinguish between synthetic ester oils, glycerides and mineral oils. He used silica gel G layers and chloroform-benzene (70 + 30) as solvent. The oil spots can be located in UV light or by spraying with concentrated sulphuric acid and subsequently heating to 160° C [14]. 

Ruororubbers and silicones are the best materials to make seals resistant to extreme temperature conditions. Viton, a fluororubber marketed by M/S Du Pont USA, can operate at 200°C in contact with oils and lubricants. Polysulfide rubbers have low compression set, but exhibit excellent fuel resistance. For improved compression set, it is admixed with relatively cheap conventional nitrile rubbers. The fluorine-containing rubbers, such as fluororubber, possess outstanding resistance to heat, fuels and hydraulic fluids coupled with extremely good aging characteristics. The reversible physical effects with respect to the ultimate tensile strength of this rubber vulcanizate is a noteworthy phenomenon since this is not associated with the deterioration of the rubber itself. Fluororubber is resistant to most fluids used in the aircraft industiy, such as synthetic, ester type lubricants, aromatic and aliphatic hydrocarbons, and water. 

Lard and vegetable oil, both ester-type compounds derived from natural sources, have been used as lubricants throughout human history. After World War II, thousands of synthetic esters were prepared and evaluated as lubricant base stocks for jet engine lubricants. ... 

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