![]() ![]() In precise, we can say that viscosity will increase when cold and decreases when heat. Thermal oxidation stability: refers to the viscosity index improver after undergoing thermal oxidative decomposition, resulting in a decrease in viscosity, an increase in acid value, an increase in carbon deposits, and sticky rings.ģ. Low viscosity index indicates high viscosity changes with change in temperature and high viscosity index is just the reverse. Low temperature starting is commonly used to characterize low temperature starting viscosity (CCS). (It also applies to fluids like engine and automatic transmission oils, gear lubricants, and power-steering fluids. Low temperature performance: It mainly refers to low temperature starting and pumping performance. Viscosity index is a dimensionless number that represents how the viscosity of a hydraulic fluid changes with temperature. Prior to understanding the viscosity index, we need to comprehend the physical property of fluids called Viscosity. 13.5) it is rounded to the nearest even number. Viscosity Index is rounded to the nearest whole number. If you have the viscosity in centiPoise, divide the centiPoise value by the oil's viscosity to get centiStokes. Common evaluation methods include ultrasonic, diesel nozzle, and 元8. This calculator uses centiStokes (cSt), which are equivalent to mm2/s. A viscous agent with poor shear stability will cause the main chain to break under the action of shear stress, reduce the molecular weight, and reduce the viscosity of the oil, causing wear and fuel consumption to increase. The lower the VI, the greater the change of viscosity of the oil with temperature. Shear stability (S): Refers to the oil's ability to resist shear, maintain viscosity and viscosity-related properties unchanged. Answer (1 of 2): Index is an arbitrary measure for the change of viscosity with variations in temperature. The higher molecular weight, the stronger thickening performance. Therefore, a 0W40 is better than a 10W40, since both offer the same viscosity (SAE40) at running temperature, but the SAE 0W will circulate more readily during a cold start than a SAE 10W. The thickening ability is bigger, the dosage of VI improver is smaller, it’s economical.The thickening power is related to chemical compound and relative molecular weight. As noted, Synthetics usually have a naturally higher viscosity index than even the artificially increased VI of mineral oils. Thickening performance (D): It refers to viscosity of oil increase when adding VI improver. In China, there are four kinds of viscosity: OCP (ethylene-propylene copolymer), PMA (polymethacrylate), PIB (polyisobutylene), and HSD (hydrogenated styrene-isoprene copolymer).Ģ. Evaluate the performance of viscosity index improver in oil Viscosity index improver is also named thickening agent, which are mainly used in engine oil, hydraulic oil, automatic transmission liquid and gear oil, it is important additive to improve viscosity, viscosity index, viscosity-temperature properties of base oil. 1. The effect of viscosity index improver on the performance of lubricant oil
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