1. Viscosity
Viscosity is the internal resistance of the fluid when the liquid flows, that is, the internal friction of the oil, and it is an indicator of the oiliness and fluidity of the oil. The higher the viscosity, the higher the oil film strength and the worse the fluidity. Generally speaking, the thickness of the lubricant film refers to the viscosity.
2. Viscosity index
The viscosity of lubricating oil has a great influence on the effect of lubrication, and temperature is the most important parameter that affects viscosity. The viscosity index (VI) is the most widely used to evaluate the viscosity-temperature characteristics of oil, which is an important quality indicator of lubricants. The higher the viscosity index, the less the viscosity of the oil is affected by temperature, and the better its viscosity-temperature performance.
3. Pour point and freezing point
The pour point is the lowest temperature at which a sample cooled under the specified conditions can flow, and the freezing point is the highest temperature at which the sample is cooled to stop moving under the specified conditions, both expressed in °C. The pour point or freezing point is a conditional test value and is not equal to the actual flow limit.
4. Flash point
The flash point of lubricating oil is a safety index for the storage, transportation and use of lubricating oil, and it is also an index for volatility of lubricating oil. The flash point is an indicator of the evaporation of oil. The lighter the distillate of the oil, the greater the evaporation and the lower its flash point. Conversely, the heavier the oil fraction, the lower the evaporation and the higher the flash point.
5. Burning point
The ignition point is also called the ignition point, which refers to the temperature at which the mixture of steam and air on the surface of the combustible liquid contacts the fire and the flame can continue to burn for no less than 5s. Can continue to measure in the same standard instrument after measuring the flash point.
6. Ash content of lubricating oil
The ash content of lubricating oil is the residue (incombustibles) left after the lubricating oil is completely burned under specified conditions. The ash content of lubricating oil is mainly composed of metal salts and metal oxides formed after the lubricating oil is completely burned. The ash content of lubricants containing additives is higher.
7. Residual carbon value
Asphaltenes, colloids and polycyclic aromatic hydrocarbons in lubricating oil are the main substances that form carbon residue. Therefore, carbon residue is an indirect indicator of colloidal substances and unstable compounds in oil. The greater the carbon residue, the more unstable hydrocarbons and colloidal substances in the oil, and vice versa.
8. Anti-corrosion
The ability of lubricating oil to delay the rust of metal parts is called rust resistance. The commonly used rust determination method is GB/T11143-89. Secondly, the presence of acidic substances in the oil will also promote rust. In order to improve the anti-rust performance of oils, some polar organics, namely anti-rust agents, are often added.
9. Corrosion resistance
The corrosion resistance of oil is measured by the degree of corrosion of the oil on the copper sheet under certain temperature conditions to evaluate the corrosion resistance of the lubricant. The corrosion of lubricating oil is mainly due to some acidic substances, oxidation products and metal reactions in the oil.
10. Demulsibility (water separation)
Emulsification is a phenomenon in which one liquid is fully dispersed in another liquid to form an emulsion. Emulsion is a two-phase system in which two liquids are mixed but not dissolved.
