Grease is mainly composed of thickener, base oil and additives. Generally, the content of thickener in lubricating grease is about 10%-20%, the content of base oil is about 75%-90%, and the content of additives and fillers is less than 5%.
l. Base oil
The base oil is the dispersion medium in the grease dispersion system, which has a great influence on the performance of the grease. Generally, medium and high viscosity petroleum lubricating oil is used as the base oil for general lubricating grease, and some synthetic lubricating oil is used as the base oil in order to meet the needs of mechanical lubrication and sealing working under harsh conditions, such as ester oil, silicone oil, Polyalpha-olefin oil, etc.
2. Thickener
Thickener is an important component of lubricating grease. Thickening agent is dispersed in base oil and forms the structural skeleton of grease, so that base oil is adsorbed and fixed in the structural skeleton. The water resistance and heat resistance of the grease are mainly determined by the thickener. There are two broad categories of thickeners used to prepare greases. Soap based thickeners (i.e. fatty acid metal salts) and non-soap based thickeners (hydrocarbon, inorganic and organic).
Soap base thickeners are divided into three types: single soap base (such as calcium base grease), mixed soap base (such as calcium sodium base grease), and complex soap base (such as complex calcium base grease). 90% of greases are made with soap-based thickeners.
3. Additives and fillers
A class of additives is required for lubricating grease, called peptizer, which makes the combination of oil and soap more stable? Such as glycerin and water. Once water is lost in calcium-based grease, its structure is completely destroyed and cannot be formed into grease. For example, glycerin can adjust the consistency of grease in sodium-based grease. Another type of additive is the same as that in lubricating oil, such as antioxidant, anti-wear and rust inhibitor, but the amount is generally more than that in lubricating oil. Such as phosphate ester, ZDDP, Elco extreme pressure anti-wear agent, compound agent, dropping point improver, etc. Sometimes, in order to improve the ability of grease to resist loss and enhance lubrication, some graphite, molybdenum disulfide and carbon black are often added as fillers.
