There are three categories of viscosity index improvers:
- OCP (Olefin Co-Polymers)
- PMA (polymethacrylate)
- PIB (polyisobutylene)
There are many different types of viscosity index improvers. The effectiveness of one viscosity index improver depends on the kind of additive in the oil. For example, an anti-separation additive is often used when a viscosity index improver reduces the viscosity index of an oil. Suppose you add a viscosity index improver to the oil without using an anti-separation additive. In that case, it will be challenging to eliminate the film separating from the metal surface.
A viscosity index improver (VI) is a kind of additive used to improve oil's stability and flow properties. For example, most motor oils use VI improvers to enhance the base oil's viscosity index (VI) or kinematic viscosity at 100°C. VI measures how much two oils with the same base oil and similar VI ratings differ in their actual viscosities at a given temperature. The higher the VI value, the more stable the oil is at high temperatures, which is essential for maintaining good engine performance.
A variety of VI improvers are available, each with its unique properties. These differences in performance can mean that you might need to use a different types of VI improvers for each application where you want to achieve specific results. For example, suppose you're using engine oil containing a high concentration of VI improvers. In that case, it might be best to choose an additive with good thickening performance—so that your engine continues to run smoothly even as its temperature increases. However, if you're using a particular type of lubricant where you don't need as much thickening power—like in your transmission or gearbox—you can opt for an additive with less intense thickening abilities.
Different viscosity improvers give you distinct performance capabilities, and each works to solve a particular problem. As we've discussed, viscosity improvers refer to additives that increase oil's viscosity. There are two types of viscosity improvers:
- Primary and Secondary:
Primary viscosity improvers work to thicken the oil by increasing its molecular weight through a reaction with the oil molecules. In comparison, a secondary viscosity improver increases the viscosity of individual oil molecules by adding a polymeric structure without any reaction with the oil molecules.
Briefly, shear stability refers to oil's ability to resist shear, maintain its viscosity, and keep its viscosity-related properties unchanged under shear stress. High-viscosity oil will cause the main chain to break under the action of shear stress, reduce molecular weight, and increase fuel consumption. Standard evaluation methods include ultrasonic detection, diesel nozzle measurement (DIN 51524), and L38 test (ASTM D2270).
Viscosity is a crucial quality of lubricating oil. Viscosity is an index to the internal resistance of a fluid that flows under gravity or in a capillary tube. Higher viscosity oils provide higher load-carrying capacity, while lower viscosity oils provide higher energy dissipation capability.
Viscosity Index (VI) improvers are polymers added to mineral base oils to improve the viscosity index of the base oil. Improving VI is particularly important for lubricants required to handle high loads at low temperatures.
The viscosity index (VI) number indicates how a lubricant would perform under high temperatures. It suggests the lubricant's consistency over various temperatures and its resistance to breakdown. That is determined by how quickly the lubricant thins when heated.
In most cases, VI improvers are made from aromatic hydrocarbons and have chemical structures similar to those used to make plastics. When a VI improver undergoes thermal oxidative decomposition, it decreases viscosity, increases acid value, and increases carbon deposits and sticky rings. Therefore, thermal oxidation stability represents the ability of VI improvers to withstand thermal oxidative decomposition and maintain viscosity and film strength; conversely, it means the extent to which VI improvers deteriorate when exposed to thermal-oxidative conditions.
A typical example of a VI improver that provides good thermal oxidation stability with good high-temperature performance is tri-(2-Ethylhexyl) phosphate (TEHP). TEHP allows for lower compression ratios and helps provide excellent fuel economy while still allowing for proper engine protection and performance.
When it comes to Viscosity Index Improvers, You must be willing to take a multi-faceted approach. There are many different types and styles of viscosity index improvers that can be utilized depending on the individual needs of your formula.