Lubricating oil generally consists of two parts: base oil and additives. Base oil is the main component of lubricating oil and determines its basic properties. Additives can compensate for and improve the performance of base oil, endowing it with certain new properties, and are an important component of lubricating oil.
Lubricating grease is mainly composed of three parts: thickener, base oil, and additives. The content of thickener in general lubricating grease is about 10% -20%, the content of base oil is about 75% -90%, and the content of additives and fillers is below 5%.
1. Base oil
Base oil is the dispersion medium in the lubricating grease dispersion system, which has a significant impact on the performance of the lubricating grease. Generally, petroleum lubricating oil with medium viscosity and high viscosity is used as the base oil for general lubricating grease. Some of them use Synthetic oil as the base oil to meet the requirements of mechanical lubrication and sealing under harsh conditions, such as ester oil, silicone oil, polymer α- Olefin oil, etc.
2. Thickener
Thickener is an important component of lubricating grease. Thickener is dispersed in the base oil and forms the structural framework of the grease, allowing the base oil to be adsorbed and fixed in the structural framework. The water resistance and heat resistance of lubricating grease are mainly determined by the thickening agent. There are two main types of thickeners used to prepare lubricating greases. Soap based thickeners (i.e. fatty acid metal salts) and non soap based thickeners (hydrocarbons, inorganic, and organic).
There are three types of soap based thickeners: single soap based (such as calcium based grease), mixed soap based (such as calcium sodium based grease), and composite soap based (such as composite calcium based grease). 90% of lubricating grease is made with a soap based thickener.
3. Additives and fillers
One type of additive is lubricating grease, called a glue solvent, which makes the combination of oil and soap more stable, such as glycerol and water. Once water is lost in calcium based lubricating grease, its structure is completely destroyed and cannot form grease. For example, glycerol in sodium based lubricating grease can adjust the viscosity of the grease. Another type of additive is the same as in lubricating oil, such as antioxidant, anti-wear, and rust inhibitor, but the dosage is generally more than in lubricating oil. Such as phosphate esters, ZDDP, Elco extreme pressure and wear resistant agents, composite agents, drop point improvers, etc. Sometimes, graphite, Molybdenum disulfide and carbon black are often added as fillers in order to improve the resistance of grease to loss and enhance the lubrication ability.
You will find that lubrication is basically similar to the composition of lubricating grease, except that lubricating grease has an additional thickening agent. (Test Article)