General

The idea of lubrication has been used for centuries. Ancient civilizations like the Egyptians used lubricants to move massive stone blocks, and Romans used them to lubricate their chariot axles. 

But then, these lubricants were made from plants and animal fats. After the Industrial Revolution, the demand for machinery lubrication increased, so petroleum-based lubricants became common. 

Composition Of Lubricants

Industrial lubricants are mostly (70-90%) composed of base oil, which provides key properties like thickness, stability, and flow. The rest are additives, which have been used since the 1920s to improve performance. The lubricant market has grown significantly, with an increase of USD 64.34 billion in 2022, along with ongoing research to meet stricter standards. However, creating the ideal lubricant is still a challenge for the leading manufacturers and marketers. 

To see why additives are necessary in  the lubricant industry, we first need to understand how the oil works in the car or machines.

Engine bearings need thick substance like the lubricant film to keep moving parts apart. This is hydrodynamic lubrication. Rolling bearings have a thinner film and deform under pressure (elasto-hydrodynamic lubrication). Cams and tappets often have metal-to-metal contact( boundary lubrication). Priston rings experience all these conditions. Lubricants work in all these situations and additives help them to do it.

Additives And Co-polymers For Lubricants

The main job of the additives is to improve the base oil performance in different situations and meet the needs of the machines. These are the small particles that work wonders to enhance the power of the lubricants and make them long-lasting. Additives and specialty chemicals makers often sell mixes of additives after diluting them in a base oil. Lubricant makers then add the right amount of this mix to their lubricants. The use of the additives depends on their purpose, how they interact with other additives, and the rules set by lubricants and the automotive industry. 

The lubricant additive can be categorized into different kinds that are based on their performance and general role for the performance of lubricants. 

The first class of additives are the surface protective additives. These are anti-wear additives, extreme pressure additives, corrosion inhibitors, detergents, and dispersants.

The second class of additives are known as the performance additives. These are viscosity index improvers, viscosity modifiers, friction modifiers, pour point depressants. 

The third class of additives, known as lubricant protective additives, counteract the negative effects or changes that take place during the performance of lubricants.  These are antifoam and antioxidants. Others, like demulsifiers or biocides, are used for specific needs.

Types Of Lubricant Additives

Pour Point Depressants

Pour point depressants help lubricants to flow at low temperatures. Normally, paraffin in oil turns to wax below 50°C, which makes oil thick and hard to pump. These additives prevent wax crystals from growing and keep oil flowing. These are used in small amounts in lubricants for machines like bearings and gear that work in cold temperatures. These additives allow the oil to flow and protect the moving parts even when cold. Modern engine oils use these additives to work in temperatures as low as -32°C. 

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Viscosity Index Improvers

Viscosity index improvers are known as the viscosity modifiers. They help lubricants stay thick at various raging temperatures like the extreme cold or extreme heat. These additives come in various forms and qualities. Some common types are polymethyl methacrylate, olefin copolymers, and hydrogenated poly(styrene-co-butadiene or isoprene).

These additives are long, flexible molecules that expand and spread out as the temperature rises and make the oil thicker. They also get tangled together, trap smaller oil molecules, and further enhance the oil’s viscosity.

The quality of the viscosity index improvers affects how much the lubricant’s thickness changes under pressure. In heavy-duty machines, the pressure can squeeze the VII molecules while making them line up and get shorter. This lowers the oil’s thickness. When the pressure drops, the molecules return to their normal shape, and the oil thickness again.

Anti-Wear Agent

Anti-wear additives protect metal surfaces when the lubricant film gets thin. They stick to the metal and form a protective layer. This layer wears away, and instead of the metal, it also gets used over time. Most of these are phosphorus compounds. Zinc dialkyl dithiophosphate (ZDDP) has been in use since the 1940s and is the most common.  However, its use in cars has decreased because zinc can damage exhaust systems. These additives work as antioxidants and corrosion inhibitors. Other additives, like ash-less additives, are expensive and needed in large amounts. So far, ZDDP is still the most cost-effective choice.

Antioxidants

Antioxidants help lubricants last longer by slowing down its oxidation. This happens over time, but heat, wear particles, water and contaminants speed it up. oxidation creates acids and sludge, which can damage metal parts and thicken the lubricant. Antioxidants, like zinc, dialkyldithiophosphates and hindered phenols are used in almost all oils and greases. They break down harmful substances and stop damaging reactions.

Defoamants

Defoamants stop developing foams in lubricants. Forms are formed when oil mixes with air, which causes problems like poor heat transfer and reduced lubrication. Silicon polymers (polymethylsiloxane) are organic co-polymers that are used to prevent foaming in the oil. These additives don’t dissolve in oil, so they can be spread evenly. They stick to air bubbles and make them bigger. The larger bubbles rise and break and release the trapped air. This happens because the additives spread and weaken the bubble’s surface.

Extreme Pressure Additives

These additives are used in heavy-duty gears and bearings to reduce friction and wear under high pressures and temperatures. EP forms a protective layer on metal surfaces, which prevents damage and seizing.  This layer also helps smooth the surface, distribute the load, and wear evenly. EP additives must react quickly to form a thick protective film under extreme conditions. They usually contain sulfur,  phosphorus, chlorine, and boron. In some cases, ashless EP additives are used to avoid corrosion from chlorine.

There are many other additives that are used for multiple purposes. Emulsifiers help oil and water mix in metalworking fluids. Without these additives, oil and water cannot mix. 

Other additives are demulsifiers, which are the opposites of emulsifiers. They prevent problems like foaming and corrosion in the oil.

Biocides are used in water-based lubricants to stop bacteria from growing.

Chempol is the leading provider of all these high-quality additives, which are designed with advanced technology. You can consult our experts on our website.