Regarding the performance of lubricating grease, the following eight points are summarized here, hoping to help everyone.

1. Viscosity

Grease is usually expressed in terms of viscosity or similar viscosity. When specifying the viscosity of grease, temperature and shear temperature must be specified. Similar viscosity specifications can be used to control low temperature fluidity and pumpability.

2. Thixotropy

The most basic property of grease is thixotropy. When an external force is applied, the flow of the grease gradually softens and the surface viscosity decreases, but once at rest, after a period of time (for a short time), the consistency increases again (that is, it returns to the original), this characteristic is called contact transsexual. This characteristic of grease determines that it can lubricate parts that are not suitable for lubricating oil.

3. Low temperature fluidity

One of the important indicators to measure the low temperature performance of grease is the low temperature torque, that is, the degree to which the grease blocks the rotation of the low-speed flow bearing at low temperature (below -20°C). The low temperature torque of the grease is represented by the average value of the starting torque and the torque after turning 60MM.

4. Strength limit

The strength limit of grease refers to the minimum shear stress required to cause the sample to start flowing, also known as the ultimate shear stress. The strength limit temperature of grease is a function of temperature. The higher the temperature, the smaller the strength limit of the grease, and the lower the temperature, the greater the strength limit of the grease. Its size depends on the type and content of the thickener, and the process of making grease. conditions are related.

5. Dropping point

The lowest temperature at which the grease reaches a certain fluidity under the specified speculative handle is called the dropping point. The dropping point of the grease helps to identify the type of grease and roughly estimate the maximum service temperature of the grease. Generally speaking, for soap base grease, the service temperature should be 20-30°C lower than the dropping point. The higher the dropping point, the higher the temperature. The better the heat resistance.

6. Evaporability

Evaporability (degree) of grease indicates the degree of volatilization of grease when it is used for a long time under high temperature conditions. The less evaporative the better. The evaporation of grease mainly depends on the nature and distillate composition of the grease.

7. Colloidal stability

The colloidal stability of lubricating grease refers to the stability of the colloidal structure of the lubricating grease under a certain temperature and pressure to prevent the lubricating oil from separating out of the lubricating grease, that is, the ability of the lubricating grease to resist oil separation. It is usually expressed by converting the quantity of lubricating oil out to mass fraction. The colloidal stability of lubricating grease reflects the oil separation trend of grease in long-term storage and actual application. If the colloidal stability of lubricating grease is poor, serious oil separation will easily occur under the action of heat, pressure, centrifugal force, etc. Thickens and dries the grease and loses its lubricating effect.

8. Oxidative stability

Oxidative stability means that the grease resists the action of heat and oxygen during long-term storage or long-term high-temperature use, and keeps its properties without permanent changes. Due to oxidation, the content of free bases or the content of free organic acids tends to decrease, and the dropping point decreases. , Appearance color deepens, peculiar smell occurs, consistency, strength limit, similar viscosity decreases, corrosive products and substances that destroy the grease structure are generated, causing soap and oil to separate. Therefore, in the long-term storage of grease, it should be stored in a dry and ventilated environment to prevent sunlight exposure, and changes in free alkali or free organic acid, corrosiveness and other items should be regularly checked to ensure its quality and performance.

The above are the eight major points about the performance of grease. Hope it will be helpful for you to understand.