What factors are related to the viscosity of base oil?
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My plant mainly produces base oils with viscosities of 75N, 150N, 250N, 350N, and 500N. The kinematic viscosity of these base oils at 40 degrees Celsius is controlled to be around 13, 30, 46, 70, and 120 respectively. We control the viscosity of the products by adjusting the temperature at which the product is extracted from the process stream. However, analytical tests such as those for boiling point range, flash point, and density cannot be used to distinguish between these different oils. In terms of boiling point range, there is hardly any difference between the first and last boiling points; for example, the second and third drying points are essentially the same, as are the flash point and density. Yet, the kinematic viscosity at 40 degrees Celsius differs significantly. Therefore, in practice, we have to adjust the extraction temperature based on the viscosity values obtained through analytical tests. Why do oils have similar boiling point ranges but yet such different viscosities? What factors can affect the viscosity of oils? ? ?
1. It is related to external pressures. When the external pressure exceeds 5 MPa, the viscosity increases as pressure rises; once it reaches a certain level, the material becomes plastic. The variation in particle size with pressure is related to the oil’s temperature and composition. 2. Related to impurities. When the lubricating oil contains metal particles, dust, carbon residues, and asphaltenes, its viscosity increases ； Its viscosity decreases when there is moisture and fuel oil mixed in. 3. It is related to its own chemical composition.
The chemical composition has an impact, as do impurities; although the boiling range is similar, there are still differences.