With the development of industrial technology, high speed, high performance, high automation, high efficiency and long life required by modern equipment, it is difficult to meet the lubrication of mineral oil alone. Adding a small amount of other substances to the lubricating material can improve its performance and give it new properties. These substances are called additives for lubricating oils.
Adding different additives to the oil is the most economical and effective means of improving oil quality. Generally speaking, the quality of lubricating oil often depends on the variety and quality of additives. Therefore, the development and use of additives has become an important way to rationally and effectively utilize resources, improve equipment performance and save energy.
Lubricating oil additives can be divided into clean dispersing agents, anti-oxidant anti-corrosive agents, extreme pressure anti-wear agents, oil-based agents and friction modifiers, antioxidants and metal deactivators, viscosity index improvers, rust inhibitors, and Grouping of coagulants, anti-foaming agents, etc., In the past two weeks, we have talked about part of the mechanism of action of additives. Next we continue to introduce the mechanism of action of other commonly used lubricant additives.
- Viscosity index improver
Viscosity index improvers, also known as tackifiers or viscosity agents, are second only to detergent dispersants. The viscosity index improver is an oil-soluble chain polymer having a molecular weight ranging from tens of thousands to several millions.
The viscosity index improver is dissolved in the lubricating oil, and they are present in the form of a filament at a low temperature, which has little effect on the viscosity of the lubricating oil. As the temperature of the lubricating oil rises, the wire roll stretches, the effective volume increases, and the resistance to the lubricating oil increases, resulting in a relatively significant increase in the viscosity of the lubricating oil.
Since the viscosity index improver has different morphology at different temperatures and has different effects on viscosity, it can increase the viscosity and improve the viscosity-temperature performance. Therefore, the viscosity index improver is mainly used to improve the viscosity index of the lubricating oil, improve the viscosity-temperature performance, and increase viscosity. The viscosity index improver can be used to prepare thickened oil, so that the prepared oil has excellent viscosity-temperature performance, so that the oil has good low temperature startability, low fuel consumption and certain anti-wear effect.
Viscosity index improvers are widely used in internal combustion engine oils, mainly for the production of multi-stage gasoline and diesel engine oils, as well as hydraulic oils and gear oils. Commonly used viscosity index improvers are: polyisobutylene, polymethacrylate, ethylene/propylene copolymer, styrene and diene copolymer, and polyethylene n-butyl ether.
2, pour point depressant
After the temperature of the oil drops to a certain extent, it will lose its fluidity and solidify. The function of the pour point depressant is mainly to lower the freezing point of the oil and ensure that the oil can flow at low temperatures. The oil contains wax. At low temperatures, the high melting point paraffin hydrocarbons are often precipitated by needle-like or flaky crystals, and are interconnected to form a network structure to form a crystalline skeleton. The low melting point oil is adsorbed and surrounded, such as a water-absorbing sponge, causing the entire oil to lose fluidity. The pour point depressant has two functions of adsorption and eutectic. Although the pour point depressant can not prevent the precipitation of wax crystals, it can change the structure of the wax.
The pour point depressant adsorbs on the wax crystal surface or forms eutectic with it, changing the shape and size of the wax crystal, preventing the wax crystal grain from forming a three-dimensional network structure, thereby maintaining the fluidity of the oil at low temperature. Pour point depressants are widely used in various types of lubricating oils, typically represented by alkyl naphthalenes, polymethacrylates and polyalphaolefins.