Lubricants additive depletion

After a short period of use in the average engine, changes start to occur. Initially, a loss of the zinc based antiwear/antioxidant additive ZDDP is observed by negative absorptions at 1000 cm 1 and 715 cm 1. Oxidative degradation of oil follows soon after and this is observed by positive absorptions, represented by carbonyl, hydroxy, nitro and C-O- species. The ER spectroscopy of lubricants can reflect additive depletion and the formation of oxidation products (Coates and Setti, 1984 Coates etal., 1984). 

If the water is introduced continuously at a rate that surpasses the rate of emulsification, the interfacial impedance will continue to remain extremely low. Contribuhon of adsorbing film lubricant additives to charge-transfer processes becomes virtually nonexistent imtil the water is depleted from the surface due to electrolysis, emulsification, and evaporation [21]. Negative effects of a water leak into automotive and hydraulic lubricants, such as impairment of the lubricant film, oil-additive precipitation, formation of water pockets on the surfaces, and accelerated corrosion have all been previously reported [2]. 

Extending the inteiwal between oil changes in automobiles and machinery is another way to conserve lubricants. Oil life is limited by depletion of oil additives, overheating, chemical contamination, and contamination of the oil by foreign particles. Using improved additives and filtering of particles, oil life can be considerably extended. 

The lubricated squeezing flow technique was applied to melting American cheese where an Universal Testing Machine with lubricated platens was employed (Campanella et al., 1987) to obtain experimental data. This technique is particularly well suited for highly viscous semisolid foods prone to either slip or require considerable effort in pressure-driven methods, such as melted cheese, cheese spreads, com massa, tomato pastes, mayonnaise, and peanut butter, and provides data at low values of strain rate of the order of about 0.01 s Conversely, it is not easy to obtain high strain rates with Universal Testing Machines. In addition, it should be ensured that the lubricant is not depleted and is in place during a biaxial strain experiment. 

Plastic pipes are polymeric in nature (e.g., polyvinyl chloride). Within the pipe are traces of the monomers used in the manufacture of the pipe (e.g., vinyl chloride). In addition, there are a variety of other chemicals added during the manufacture of the pipe as lubricants to facilitate their manufacture or stabilizers to prevent the breakdown of the pipe. In Europe, lead has been used as the stabilizer for pipes, whereas various organic tin compounds have been utilized in the United States. Lead is widely recognized as being toxic. Inorganic tin has a very limited toxicity, but this is not the form of tin that is used. Some of the organic tin compounds are potent nervous system toxins (e.g., trimethyl or triethyl tin), while others appear to adversely affect the immune system (dioctyl tin). The forms of tin used in polyvinyl chloride pipe, however, are primarily monomethyl and dimethyl tin, which are much less active as neurotoxins than the trimethyl tin. There will be some extraction of all these chemicals from the pipe when it is first put into service. However, the concentrations that are found in the water decrease sharply with continued use of the pipe. This is only partially due to the depletion of the chemical from the pipe because continuous water flow will form an impermeable barrier (e.g., calcium carbonate) on the interior of the pipe that minimizes leaching from its surface. 

Sasaki, A., Tobisu, H., and Uchiyama, S. (February 15-17 2008) How to judge depletion of oxidation inhibitors and how to simulate necessary top-up fresh oil to recover depleted additive. In CD Proc. 16th International Colloquium Tribology, Lubricants, Materials and Lubrication Engineering, Stuttgart/Ostfildem, Germany. 

Most lubricant blends contain a variety of additives to improve lubrication performance for specific machinery applications. As the oil ages in a machine or is exposed to various contaminants, respective additives are consumed (Fig. 16.3). For instance, antioxidants serve to retard the degradation process. However as the additive is depleted, the rate of oxidation increases rapidly until complete lubricant failure occurs. 

The critical temperature of lubricated friction has been related to the physical chemistry of adsorption by interpreting the transition from smooth sliding with a low coefficient of friction to high values of friction with scuffing as the critical depletion of the adsorbed lubricant film. The critical transition temperature is identified with the critical temperature of desorption. Frewing [31] developed the following relation for the stable existence of a film of adsorbed additive in equilibrium with its oil solution ... 

As described above, plants have evolved the ability to produce a diverse range of fatty acid structures. Several specialty fatty acids have already been extensively exploited for industrial uses such as lubricants, plasticizers, and surfactants (Table 2). In fact, approximately one-third of all vegetable oil is now used for non-food products, and this figure is expected to increase as petroleum reserves are depleted. Thus, in addition to providing food, oilseed crops can be considered efficient, low polluting chemical factories which are... 

This paper shows the feasibility of a novel experimental analysis of the rheology of a ZDDP tribofilm. The tribofilm thickness is evaluated at about 14 nm. The test consists in partially removing the tribofilm on a steel surface and to run a friction test on the modified surface. Using triboscopic analysis of both friction and ECR measru ements, information on the tribofilm durability are visualized mder different lubrication conditions. Unlubricated contact conditions are quite severe, and the use of dodeccme lowers this severity. The use of PAO resulted in a particular case where all additives of the lubricant have been depleted. Both mechanical and chemical removal mechanisms seem to be involved. 

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