Maro Publications

Lubricants

Notes

*6/26/2012 
from 6/25/2012

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Personal Lubricants

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Notes

“A lubricant is a substance introduced to reduce friction between moving surfaces. It may also have the function of transporting foreign particles. The property of reducing friction is known as lubricity.

A good lubricant possesses the following characteristics:

 High boiling point.

 Low freezing point.

 High viscosity index.

 Thermal stability.

 Corrosion prevention.

 High resistance to oxidation.

One of the single largest applications for lubricants, in the form of motor oil, is protecting the internal combustion engines in motor vehicles and powered equipment.

Typically lubricants contain 90% base oil (most often petroleum fractions, called mineral oils) and less than 10% additives. Vegetable oils or synthetic liquids such as hydrogenated polyolefins, esters, silicones, fluorocarbons and many others are sometimes used as base oils. Additives deliver reduced friction and wear, increased viscosity, improved viscosity index, resistance to corrosion and oxidation, aging or contamination, etc.

Lubricants such as 2-cycle oil are added to fuels like gasoline which has low lubricity. Sulfur impurities in fuels also provide some lubrication properties, which has to be taken in account when switching to a low-sulfur diesel; biodiesel is a popular diesel fuel additive providing additional lubricity.

Non-liquid lubricants include grease, powders (dry graphite, PTFE, Molybdenum disulfide, tungsten disulfide, etc.), PTFE tape used in plumbing, air cushion and others. Dry lubricants such as graphite, molybdenum disulfide and tungsten disulfide also offer lubrication at temperatures (up to 350 °C) higher than liquid and oil-based lubricants are able to operate. Limited interest has been shown in low friction properties of compacted oxide glaze layers formed at several hundred degrees Celsius in metallic sliding systems, however, practical use is still many years away due to their physically unstable nature.

Another approach to reducing friction and wear is to use bearings such as ball bearings, roller bearings or air bearings, which in turn require internal lubrication themselves, or to use sound, in the case of acoustic lubrication.

In addition to industrial applications, lubricants are used for many other purposes. Other uses include cooking (oils and fats in use in frying pans, in baking to prevent food sticking), bio-medical applications on humans (e.g. lubricants for artificial joints), ultrasound examination, internal examinations for males and females, and the use of personal lubricant for sexual purposes.”

(Wikipedia, Lubricants, 6/25/2012)

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“Industrial lubricating greases are homogeneous products of semi-liquid to solid consistency. Essentially, they consist of a dispersion of a thickener in a liquid lubricant or base oil. In general, the thickener is a significant determinant of the properties of the greases.

Polyurea compounds are among the thickeners used in making greases. Often the polyurea compounds are prepared directly in the base oil by the reaction of amines with isocyanates.

One method to test the performance of greases is cone penetration and prolonged working of lubricating greases through ASTM D217. A cone of specified weight is allowed to fall into a lubricating grease sample at 25.degree. C. The depth of the cone, in tenths of a millimeter, identifies the consistency of the grease. With the use of Table 1, the NLGI grade of the grease is identified from the 60 stroke”

[Baum, US Patent 8,193,133 (6/5/2012)]

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Copyright 2012 by Roger D. Corneliussen.
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* Date of latest addition; date of first entry is 6/5/2012.