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occurs when the lubricant layer forms a continuous layer which modi¿ es the polymer-
metal interface character with the presence of metal carboxylate experiment with PVC
[13].
Hartitz delineated two groups of lubricants one of which was composed primar-
ily of metal soaps, while the other consisted of less polar components, for example
paraf¿ n waxes low molecular weight polyethylenes and oils. Metal soaps alone or in
combination with additives of the second group can delay gelation of the PVC [14].
6.3 LUBRICATION OF METAL-METAL CONTACTS
Metal-metal contacts are lubricated with lubricants and greases. Greases mainly con-
tain a mineral and vegetable oil and a thickener. Thickener types are metallic soap
thickeners, complex metallic soap thickeners, and non-soap thickeners. The non-soap
thickeners are organoclay, polyurea, and Poly Tetra Fluoro Ethylene (PTFE). The me-
tallic soap thickeners are alluminum soap, hydrated calcium soap, sodium soap, and
lithium soap. Complex metallic soap thickeners give the grease a higher temperature
boost with better oxidation and high drop points. Complex metallic soap thickeners are
alluminum complex, calcium complex, barium complex, and lithium complex [15].
This is by far the most widely used category of grease in industry today. This type of
grease varies by the additive that forms the soap in the lubricants chemical makeup.
FIGURE 1
The TEM picture of Li stearate grease [16].
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