General

Lubricant properties are measured by viscosity, high stability, performance in high and low temperatures, water resistance, and volatility. Lubrication science optimises performance by managing these properties with base oils and additives. Viscosity is key, affecting flow and protecting parts from wear.

When other forces like gravity act on a fluid, the molecules start to move against each other, causing molecular-level friction that opposes flow. The higher the internal friction, the higher the viscosity of the fluid. How a fluid’s viscosity responds to changes in temperature and pressure determines how well it can perform the basic functions of a lubricant.

When lubricant base oils cool, they thicken and solidify below a certain temperature, known as the pour point. This increases the lubricant’s load-carrying capacity and significantly impairs its circulation ability. Conversely, lubricants become thinner when heated, which reduces their work to carry a load and saves metal-to-metal contact.

Extreme pressure can also reduce oil viscosity, a process known as mechanical shearing. This decreases the lubricant’s film strength and ability to prevent metal-to-metal contact and wear. However, trying to control this by selecting a higher viscosity can end up in oil starvation, as it will not flow freely through smaller passages. The proper viscosity for the intended application is critical to ensure that the oil circulates properly and provides adequate film strength under pressure.

Viscosity: A Fluid Resistance To Flow

The viscosity index is the calculation of a fluid’s resistance to flow. It is typically measured using a kinematic or dynamic grading system that the International Organization for Standardization (ISO) or Society of Automotive Engineers (SAE) has settled.

Besides that American Petroleum Institute (API) Service Classification and SAE J-300 Engine Oils Viscosity Classification are two important standards for the authenticity of gasoline and diesel motor oils. Here are some additional details about viscosity:

• Temperature and pressure become effective on VII.
• Higher-viscosity fluids are thicker and flow more slowly than lower-viscosity fluids.
• Viscosity is important in many applications, including lubrication, hydraulics, and aerodynamics.

There are many methods to measure the fluid viscosity, including the capillary viscometer, rotational viscometer, and falling ball viscometer—equipment manufacturers (OEMs) and consumers to understand each lubricant’s functional characteristics and limitations.
Low-viscosity fluids are thinner and lighter than high-viscosity fluids. Low-viscosity motor oil (0W-20) flows faster than high-viscosity oil (20W-50).

Benefits Of A Viscosity Index Improver

• VIIs allow engine oils and drilling fluids to operate over a wider temperature range. This means you can use them in hot and cold climates without changing the oil as often.
• VIIs decrease the need for frequent oil changes. This can save money and time and reduce the environmental impact of oil disposal.
• Lubricating oils with VIIs have a longer service life. This means that users can use them for longer periods before there is a need to replace them.
• viscosity index makes oils and lubricants easier to process and flow. this can reduce the cost for manufacturers and help them improve the final product’s quality.
• High-level machine longevity and lower energy consumption result in lower production costs for industries. this helps businesses to save money and also helps them to reduce the environmental impact through smooth manufacturing.

Viscosity Modifiers And Viscosity Improvers

Oil viscosity modifiers and viscosity improvers are additives to reduce viscosity changes at high and low temperatures. This helps to keep lubricants and greases effective over a wider range of temperatures. They often come in combination with viscosity index improvers, further enhancing the performance of lubricants and greases.

Many industries offer a variety of oil viscosity modifiers and viscosity improvers, including polymers for engine fluids. These additives and polymers help to improve the performance of drilling fluids by increasing their viscosity, which allows to reduce friction and prevents them from wear and tear.

Viscosity modifiers and viscosity improvers are essential to many lubricants and greases. They help keep these products effective over a wide range of temperatures, which is important for various applications.

Formula For The Viscosity Index:

The viscosity index (VI) is a measure of how much a fluid’s viscosity changes with temperature. A high VI means that the fluid’s density varies little with temperature, while a low VI means that the fluid’s viscosity changes significantly.
The VI of a fluid can be calculated using the following formula:
VI = 100 – 100 * (log(η40) – log(η100))
Where:

• η40 is the kinematic viscosity of the fluid at 40°C
• η100 is the kinematic viscosity of the liquid at 100°C

Viscosity index improved examples include multipurpose tractor transmission fluids, automatic transmission fluids, power steering fluids, industrial gear oils, and more. These fluids are all used in applications where the liquid needs to have a consistent viscosity over a wide range of temperatures.

For example, in a transmission, the fluid must flow smoothly at low temperatures when the car is first started. Still, it must also be able to provide adequate lubrication at high temperatures when the vehicle is driving at high speeds. A high VI fluid can do both things, while a low VI fluid cannot.

Viscosity index improved fluids are made by adding additives to the base oil. These additives help to keep the liquid from thinning out at high temperatures and thickening out at low temperatures.

Major Chemicals And Polymers Used For The Formation Of Viscosity Index Improvers

Viscosity index improvers are typically made from polymers, which are long chains of molecules. When these polymers are added to a fluid, they form a network that traps the fluid molecules and prevents them from moving past each other as easily. This makes the fluid more viscous or thick.
The type of polymer used to make a viscosity index improver will determine how it performs at different temperatures. Some polymers are more effective at low temperatures, while others are more effective at high temperatures.

Viscosity index improvers are often combined with other additives, such as detergents and dispersants, to create a more complete lubricant.
Here are some of the materials commonly used to improve the viscosity index:

• Polymethacrylates (PMA)
• Radial polyisoprene
• Polyisobutylene (PIB)
• Olefin copolymers (OCP)

These materials come in different types, each with its response curve. Viscosity index improvers are normally to use in gear oils, multigrade motor oils, power steering fluids, greases, automatic transmission fluids, and hydraulic fluids.

Low temperatures allow the liquid to flow more evenly to reach the bearings quickly. At high temperatures, fluids will have a high viscosity. Even so, they offer the necessary film thickness to protect the moving parts and bearings within your tools.

A major problem with viscosity index-improving additives is that they are very sensitive to mechanical shearing. This means they can break down when subjected to high-stress levels, such as when used in engines.