Lubrication in Terms of Ion-Radical Organic Chemistry

Mechanical processing (e.g., abrasion) of metallic surfaces causes the emission of electrons this is known as the Kramer effect (Kramer 1950). The effect has been shown by the measurement of selfgenerated voltages between two metallic surfaces under boundary lubrication (Anderson et al. 1969, Adams and Foley 1975). The exoelectrons have a kinetic energy from 1 to 4 eV (Kobzev 1962) and they may initiate some chemical reactions. For instance, if the metal (whose surface has been worked) is placed in an aqueous solution of acrylonitrile, the latter forms an abundant amount of an insoluble 

Boundary lubrication is defined by the properties of the surfaces and the lubricants—the properties other than viscosity. Surface friction generates the emission of electrons, photons, ions, neutral particles, gases (e.g., oxygen), and x-rays. According to the theme of this book, reaction of organic lubricating materials with triboemitted electrons will be considered in Section 8.6. 

Electron emission occurs when plastic deformation, abrasion, or fatigue cracking disturbs a material surface. Triboelectrons are emitted from freshly formed surface. The emission reaches a maximum immediately after mechanical initiation. When mechanical initiation is stopped, the emission decays with time. Strong emission has been observed for both metals and metal oxides. There is a strong evidence that the existence of oxides is necessary. The exoelectron emission occurs from a clean, stain-free metallic surface upon adsorption of oxygen (Ferrante 1977). 

The work function of the rubbing surfaces and the electron affinity of additives are interconnected on the molecular level. This mechanism has been discussed in terms of tribopolymerization models as a general approach to boundary lubrication (Kajdas 1994, 2001). To evaluate the validity of the anion-radical mechanism, two metal systems were investigated, a hard steel ball on a softer steel plate and a hard ball on an aluminum plate. Both metal plates emit electrons under friction, but aluminum produced more exoelectrons than steel. With aluminum, the addition of 1% styrene to the hexadecane lubricating fluid reduced the wear volume of the plate by over 65%. This effect considerably predominates that of steel on steel. Friction initiates polymerization of styrene, and this polymer formation was proven. It was also found that lauryl methacrylate, diallyl phthalate, and vinyl acetate reduced wear in an aluminum pin-on-disc test by 60-80% (Kajdas 1994). 

The shortened anion has a weak CFj-OCFj bond. The degradation of this anion proceeds in a stepwise manner  

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