First, it’s important to understand the role of a thickener in a grease and how it impacts the performance of the final product.

When a grease is manufactured, the thickener is the key ingredient that turns an oil into a finished grease. The thickener gives greases their unique flow properties, allowing them to stay in place while retaining the ability to be pumped.

Different thickeners can also affect a grease’s high-temperature properties, water resistance, mechanical stability, and resistance to oxidation. These are all crucial factors that impact the suitability of the finished grease to be used in certain applications such as under prolonged working conditions or in wet or hot environments.

Although lithium and lithium complex thickeners have been used historically, there are now a range of grease thickeners that can produce desirable finished greases. So why have lithium-based thickeners been relied upon by the industry?

Lithium and lithium complex greases account for 69% of the global grease market.1 Historically lower in cost and easily available, these thickeners have offered ease of manufacture and good overall performance.

Lithium greases offered improved high-temperature performance compared to their calcium predecessors. They also benefit from good stability, water resistance and, with additional additives, can also offer extreme-pressure, anti-wear, anti-corrosion and anti-rust capabilities.

Recently, supply chain issues and demand for raw materials from other industries have significantly altered the grease market—placing a premium on lithium. This has resulted in an increase in the use of alternative thickeners in today’s greases.

Calcium sulfonate complex greases are formulated with a thickener that provides inherent extreme-pressure and anti-wear performance, meaning that additional additives are not required to deliver a high-performance grease. The thickener also offers excellent performance in the presence of water thanks to its ability to absorb a significant amount of moisture while minimizing the impact on lubrication.

Calcium sulfonate complex greases have high-temperature performance that is equivalent to the best lithium complex greases, offer excellent shear stability, and can be formulated to perform almost any role.

Polyurea thickened greases are another modern alternative. These boast a life span typically 3–5 times longer than lithium and good high-temperature performance, as the polyurea thickener does not contain any metallic ingredients. In addition, they offer a wide range of high-performance qualities, including the ability to provide vital protection while delivering outstanding rust and corrosion protection as well as thermal and oxidation stability.

However, polyurea greases can be more challenging to incorporate additives into and can be incompatible with other types of thickeners (or other polyurea greases). These challenges can be overcome, particularly when greases are formulated by experienced experts to provide superior protection for specific applications.

Aluminum complex greases offer excellent performance over a wide range of temperatures, with high-temperature performance similar to lithium complex greases and good low-temperature performance. The thickener is also reversible, meaning that it will re-form after brief excursions above its melting point. Aluminum complex greases also offer good water resistance and can be formulated to meet NSF H1 for use in incidental food contact applications.

Each grease thickener has unique properties, which means that not all thickeners and their subsequent finished greases are suitable for all applications and environments.

For example, for lower-temperature applications, calcium sulfonate greases may not be as effective due to their need for a higher thickener content to reach a specific consistency. In contrast, aluminum complex thickeners are well suited for low-temperature use, while polyurea greases may be selected over lithium or calcium sulfonate greases for high-temperature or long-life applications due to their naturally enhanced oxidation stability.

Consideration also needs to be given to where the greases will be used. For example, calcium sulfonate complex and aluminum complex grease thickeners can be used to formulate greases suitable for incidental food contact for use in food manufacturing applications. Aluminum complex greases are suited for use in off-road applications like heavy-duty mining equipment, including open gear greases.

However, it’s important to be aware that through good formulation and additive systems, greases can be designed for multiple applications. A good example of this is calcium sulfonate thickened PEERLESS™ LLG. A multi-use grease, it offers premium performance and the ability to reduce operating costs in high-temperature or wet operating conditions.