With the continuous improvement of China's industrialization level and the increasing use of advanced equipment, the working temperature of many lubrication parts is getting higher, and the requirements for the high temperature resistance of lubricating grease are also constantly increasing. The commonly used lubricating grease in China is metal soap based grease based on mineral oil, with a usage temperature not exceeding 120 ℃. Studying high-temperature lubricating grease is of great significance for meeting the high-temperature lubrication requirements of certain equipment.
1. Base oil
Base oil is the main component of lubricating grease, and the performance of base oil directly affects the performance of lubricating grease in all aspects. Mineral oil is prone to oxidation and deterioration, and generally cannot be used as a base oil for high-temperature lubricants. Synthetic oil has good high-temperature stability, oxidation stability, good viscosity temperature performance, and low volatility, which can meet various requirements under high temperature conditions. It has become the main base oil used in high-temperature lubricating grease.
2. Thickener
Thickener is an indispensable solid part of lubricating grease. Thickener thickens the base oil to a semi-solid state, and like base oil, it determines the properties of lubricating grease. There are four main types of thickeners, namely soap based, hydrocarbon based, organic, and inorganic thickeners. Alkyl thickeners are generally used at very low temperatures (less than 80 ℃), while high-temperature thickeners are mainly soap based, organic, and inorganic.
Single metal soap lubricating grease has a low operating temperature (less than 120 ℃) and cannot meet high temperature conditions. Currently, the high-temperature soap based grease used is mainly composite soap based grease, mainly including composite lithium, composite calcium, and composite aluminum, with composite lithium being the most commonly used. Organic thickeners refer to organic compounds that have thickening effects other than metal soaps and solid hydrocarbons, such as arylureas, amides, phthalocyanine pigments, and indocyanine dyes. They are mostly compounds with aromatic rings and good thermal stability. Organic thickeners form a structural framework in base oil under certain process conditions, thereby producing lubricating grease. Inorganic thickeners generally have good high-temperature performance and are ideal thickeners for manufacturing high-temperature lubricating grease. They have good high-temperature performance and high-temperature oxidation stability, but other properties such as protection and solid residue after base oil evaporation are relatively insufficient.
With the development of modern mechanical equipment, there is an increasing demand for high-temperature multi effect lubricating grease. The development of high drop point and multi efficiency lubricating grease is rapid, and composite lithium based grease and polyurea lubricating grease are the main directions for developing high drop point lubricating grease varieties. The proportion of high drop point grease in China has increased in recent years, but due to industrial development and the condition of machinery and equipment, high-temperature lubricating grease started late and developed slowly, and the variety is not yet ideal. Efforts to develop high-temperature lubricating grease, especially composite lithium based grease and polyurea lubricating grease, are currently the main direction of lubricant development in China.