Lubricants are materials that are utilized for reducing the frictional force occurring between two surfaces in mutual contact. The movement between these surfaces could generate heat and there are various other sequential actions prevalent with the movement. This primarily implicates the transportation of foreign particles, function of transmitting forces, heating of surfaces and at times cooling of surfaces as well. Lubricity is necessarily crucial in fulfilling various purposes. Rather than being incorporated in industrial applications, they are also used for medical examinations, bio-medical applications, cooking purposes (the oil employed as a lubricant in frying pans), personal purposes and ultrasound examinations.
Qualities of a robust lubricant:
An appropriate lubricant is expected to fulfill certain qualities. This essentially encompasses hydraulic stability, high viscosity index and high resistance to oxidation, demulsibility, thermal stability, low freezing point, corrosion prevention and high boiling point. Low freezing point and high boiling are pivotal for the maintenance of liquefied state for a wide range of temperature. The basic functions of a robust lubricant is to keep the moving parts apart, reduce friction and provide protection against wear and tear.
Composition of a typical lubricant:
The composition of a typical lubricant is primarily base oil and a small quantity of additives. The most commonly used base oils include synthetic liquids or vegetable oils such as esters, fluorocarbons, silicones and hydrogenated polyolefins and various other oils. Additives are incorporated for the reduction of friction, improved resistance to contamination or aging and enhanced viscosity index and overall viscosity percentage. Additives play the most crucial job of enhancing the lubricity however required in small amounts.
Categories of lubricants:
There are non-liquid lubricants as well that have been less extensively due to certain drawbacks. The most used non-liquid lubricants include PTFE, grease, tungsten disulphide, dry graphite, molybdenum disulphide and more. These lubricants are advantageous as in being able to work efficiently at relatively higher temperatures (up to 350⁰ C). This feat cannot be accomplished as in the cases of liquid and oil-based lubricants.
Dominance and preferential factors based upon demand:
Automotive applications are dominant as in lubricant usage due to the consistent requirement of lubrication. However, lubricants find significant usage in metal working applications, marine and other industrial applications. Liquid lubricants are the mostly preferred; however, gas lubricants are being employed as well. Fluid bearings are one amongst those applications requiring the usage of air based lubricants.
Aqueous lubrication and biolubrication: