The usage characteristics and basic composition of grease

Grease has the following advantages over lubricating oil.

1. It has good adhesion on metal surfaces and is not easy to drain; it can simplify the structure of the lubrication system when used in parts that are not easy to seal.

2. Resistant to rolling and crushing, and still has good lubrication ability under high load and impact load.

3. The lubrication cycle is long and does not require frequent replenishment or replacement. It also has certain rust resistance for metal parts, which relatively reduces maintenance costs.

4. The applicable temperature range is wider and the applicable working conditions are also wider.

Therefore, grease can be used in parts of the vehicle that are not suitable for liquid lubricants.On the other hand, the viscosity of grease is relatively large, resulting in large resistance during operation and large power loss. Grease also has poor fluidity and basically does not have the cooling and cleaning effects of liquid lubricants. It is difficult to remove solid impurities after being mixed in. In addition, it is difficult to add and replace grease in certain parts of use. Therefore, the parts where grease can be used are subject to certain restrictions.

Basic composition of grease

Grease is mainly composed of three parts: thickener, base oil, and additives. Generally, the thickener content in grease is about 10%-20%, the base oil content is about 75%-90%, and the content of additives and fillers is less than 5%.

1. Base oil

Base oil is the dispersion medium in the grease dispersion system, which has a great influence on the performance of the grease. Generally, greases mostly use petroleum lubricating oils of medium viscosity and high viscosity as base oils. In order to meet the needs of mechanical lubrication and sealing working under harsh conditions, some use synthetic lubricating oils as base oils, such as ester oils and silicone oils.Poly crystalline-olefin oil , etc.

2.Thickener

Thickener is an important component of grease. The thickener is dispersed in the base oil and forms the structural skeleton of the grease, allowing the base oil to be adsorbed and fixed in the structural skeleton. The water resistance and heat resistance of grease are mainly determined by the thickener. There are two main categories of thickeners used in preparing greases. Soap-based thickeners (i.e. fatty acid metal salts) and non-soap-based thickeners (hydrocarbons, inorganic and organic types).

Soap-based thickeners are divided into three types: single soap base (such as calcium-based grease), mixed soap base (such as calcium-sodium base grease), and composite soap base (such as complex calcium-based grease). 90% of greases are made with soap-based thickeners.

3. Additives and fillers

One type of additive is required for grease, called peptizing agent  , which makes the combination of oil and soap more stable, such as glycerol and water. Once water is lost in calcium-based grease, its structure is completely destroyed and cannot form grease. For example, glycerol in sodium-based grease can adjust the consistency of the grease. The other type of additives are the same as those in lubricating oils, such as antioxidants, anti-wear and anti-rust agents, but the dosage is generally higher than that in lubricating oils.