The biggest difference between grease and lubricating oil is the addition of thickener components. What does the thickener do? Today, I will mainly talk to you about the important role that thickeners play in grease as a special component.
Thickener function:
The thickener is responsible for the role of the lubricating grease as a non-Newtonian fluid, so that the lubricating oil is stored in the thickener structure and presents a solid or semi-solid state. The thickener directly determines the high and low temperature performance, shear resistance, water resistance and so on of the grease.
Different thickeners have different ability to absorb the base oil in the grease, so the weight ratio of the grease will also be different, usually distributed in 5%-20%.
Types and characteristics of thickeners:
Thickeners are generally divided into metal soap base and non-metal soap base.
Metal soap bases are divided into ordinary metal soap bases and complex metal soap bases.
Ordinary metal soap is usually obtained by the saponification reaction of fatty acid and alkali metal, and the structure is relatively simple. Alkali metals include lithium hydroxide, sodium hydroxide, calcium hydroxide and so on. Lithium soap base is widely used as a thickening agent for grease in automobile parts. It has balanced performance in all aspects, good shear resistance and high temperature resistance.
The similar complex metal soap base is usually fatty acid, which is obtained by saponification reaction between organic acid and alkali metal, and the composition contains different chain segments and molecular formulas. Compared with ordinary soap base, complex soap base products have better shear resistance and high temperature resistance.
Common non-metal soap bases are polyurea, polytetrafluoroethylene (Teflon), gel and so on.
Polyurea thickener grease has many performance characteristics, good high temperature stability, particularly good anti-vibration performance>good noise reduction effect, good oxidation resistance>long lubrication life, no melting point, and it will directly turn into ash at high temperature. But there are also disadvantages. The low-temperature starting torque is relatively large, and it will harden with time and temperature changes.
Polytetrafluoroethylene thickener is generally combined with perfluoropolyether base oil to form fluorine-based grease, which has superior high and low temperature performance, good lubrication performance, good chemical resistance, and relatively high price. From the perspective of comprehensive life and maintenance-free, the scope of application has gradually increased to various fields. Polytetrafluoroethylene can not only be used as a thickener, but also as a lubricating additive to improve the lubricating performance of grease.
As a thickener of grease, gel has the advantages of excellent noise reduction effect. The high-viscosity structure can wrap dust and has a good anti-dust effect. The disadvantage is that the low-temperature starting torque is large.
Thickener is an important factor in determining the performance of lubricating grease. It can adhere to various high-speed gears and bearings, greatly reducing the noise of parts during operation, and enabling it to obtain water and dust resistance.
Therefore, according to the parameter requirements of the location where the grease is used, the engineer's tailor-made grease formula and the combination of processes will greatly improve the performance and life of the parts.
