Grease is an essential lubricant used in many industrial applications to reduce friction and wear between two surfaces in motion. However, the effectiveness of grease depends on its ability to maintain its consistency and shear stability, which can be achieved by using an appropriate thickener. In this article, we will explore the different types of thickener used in grease, their properties, and the factors that determine their suitability for various applications.
Grease is a mixture of base oil, thickener, and additives that is designed to provide lubrication in a wide range of applications, from automotive engines to industrial machinery. The thickener in grease is responsible for maintaining its consistency, preventing the base oil from leaking out, and enhancing its shear stability. There are various types of thickener used in grease, including simple soap, complex soap, organic acid, and inorganic thickeners, each with its own unique properties and advantages.
Types of Thickeners Used in Grease
Simple Soap Thickeners
Simple soap thickeners are one of the most common types of thickeners used in grease. They are made by reacting fatty acids with a metal hydroxide or carbonate, such as lithium hydroxide or calcium carbonate. The resulting reaction product is a soap grease, which is known for its good water resistance and low cost. However, simple soap thickeners have poor oxidative resistance and are generally limited to operating conditions below 100°C.
Complex Soap Thickeners
Complex soap thickeners are a more advanced type of soap thickener that is made by reacting short-chain organic acids with a metal hydroxide or carbonate, such as lithium hydroxide or calcium carbonate. This reaction produces a complex soap that has better high-temperature properties and shear stability than simple soap thickeners. Complex soap thickeners are commonly used in lithium complex grease, which is known for its excellent shear stability and high-temperature properties.
Inorganic Thickeners
Inorganic thickeners are a type of thickener that does not contain any soap. Instead, they use inorganic compounds, such as silica, clay, or calcium sulfonate, to thicken the base oil. Calcium sulfonate greases are particularly popular due to their excellent shear stability and resistance to high temperatures and corrosive environments.
Organic Acid Thickeners
Organic acid thickeners are made by reacting an organic acid, such as azelaic acid or 12-HSA, with a metal hydroxide or carbonate. The resulting complexing acids form a short-chain complex that provides excellent shear stability and high-temperature properties. Organic acid thickeners are commonly used in diurea, tetraurea, and urea-urethane grease, which are known for their excellent shear stability, high-temperature properties, and resistance to corrosive environments.
Factors Affecting the Selection of Grease Thickeners
The selection of grease thickeners depends on several factors, including the operating conditions, equipment design, and performance requirements. The operating conditions, such as temperature, load, and speed, can significantly affect the performance of the grease and the suitability of its thickener. For example, high-temperature applications require thickeners that can withstand the extreme heat without losing their consistency or lubricating properties. Similarly, applications that require high loads and speeds may require thickeners that can maintain their shear stability under heavy stress.
Equipment design is another important factor to consider when selecting grease thickeners. The equipment design can affect the accessibility of the lubrication points, the type of seals used, and the materials of construction. Some equipment designs may require thickeners that are compatible with certain seal materials, while others may require thickeners that can penetrate hard-to-reach lubrication points.
Finally, the performance requirements of the grease can also affect the selection of its thickener. The performance requirements can include factors such as water resistance, oxidation resistance, and load-carrying capacity. For example, applications that require good water resistance may require thickeners that are hydrophobic and can repel water. Applications that require good oxidation resistance may require thickeners that are highly resistant to oxidative breakdown and can provide long-term protection against rust and corrosion.
Conclusion
In conclusion, the thickener in grease plays a critical role in determining its consistency, shear stability, and lubricating properties. There are several types of thickeners available, each with its own unique properties and advantages. The selection of the thickener depends on several factors, including the operating conditions, equipment design, and performance requirements. Bisley International provides high-quality raw materials for the production of lubricants and greases. Benzoic acid, a highly resistant industrial chemical, is one of the starting materials for the production of various chemicals, such as benzoyl chloride, benzyl benzoate, and benzyl alcohol. It is widely available and cost-effective, making it a valuable and indispensable chemical that plays a critical role in the grease and lubricants industry supply chain. By using high-quality raw materials like benzoic acid and molybdenum, Bisley International ensures that their customers receive the best possible performance from their lubricants and greases.
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