Viscosity Index Improver Performance
The thickening ability of the viscosity index improver is mainly related to the type and relative molecular mass of the viscosity index improver, and the greater the relative molecular mass, the stronger the thickening ability. The thickening ability of the viscosity index improver determines the amount of viscosity index improver added to the multi-stage engine oil. Due to the thermal oxidative decomposition of the polymer compound, the addition amount of the viscosity index improver has a significant influence on the quietness of the multi-stage engine oil. Generally, the amount of the viscosity index improver in the multi-stage engine oil is preferably not more than 1% to 1.5%.
Low temperature performance
The low temperature performance of multi-stage engine oil is mainly reflected in low temperature startability and low temperature pumpability. The lower the low temperature thickening ability of the viscosity index improver, the better the low temperature performance.
Shear stability is an important performance property of viscosity index improvers, which directly affects the stability of multi-grade engine oil viscosity. The shear stability is related to the relative molecular mass of the viscosity index improver. It is related to the molecular mass distribution and the polymer structure, but is mainly determined by the relative molecular mass. The greater the relative molecular mass of the same type of viscosity index improver, the worse the shear stability. There are several ways to improve the shear stability: one is to reduce the relative molecular mass of the viscosity index improver and to narrow the relative molecular mass distribution; the other is to maintain the polymer's high thickening ability by improving the structural stability of the polymer. At the same time, it has good shear stability.