Basic concepts of grease

(1) What is grease

    The latest definition of NLGI (National Lubricating Grease Institute): Grease is a solid or semi-solid product formed by dispersing one or several thickeners into one (or several) liquid lubricants . In order to improve certain properties, some other components (additives or fillers) are added.

(2) Thixotropy of grease

  When an external force is applied, the grease gradually softens in the flow and the apparent viscosity decreases, but once at rest, after a period of time (very short), the consistency increases again (recovers), which is the thixotropy of the grease.

This special property of grease determines that it can be lubricated in parts that are not suitable for lubrication with lubricating oil, and shows its superiority.

Grease composition

  Grease is composed of base oil, thickener and additives (including fillers).

  Base oil is a liquid lubricant, with mineral oil and synthetic lubricants.

  Thickener is a solid substance with thickening effect.

  Additives are substances added to improve certain properties of grease.

Grease composition-base oil

1. Mineral oil refers to petroleum lubricating oil.

advantage:

  It has good lubricating performance and wide viscosity range. Oils with different viscosities are suitable for manufacturing greases for different purposes; they have a wide range of sources and low prices.

Disadvantages:

  The high temperature and low temperature cannot be considered at the same time, or it cannot adapt to a wide temperature range. At the same time, it cannot meet the requirements of some special conditions such as extremely high temperature, extremely low temperature, high speed, long life, chemical resistance, and radiation resistance. To meet these severe conditions of grease, you also need a variety of synthetic oils.

Grease composition-base oil

2. Synthetic oil

  Synthetic oil refers to a large class of functional liquids synthesized by various chemical reactions. Different synthetic oils show better advantages than mineral oils in some aspects.

The commonly used synthetic oils in greases are:

  Synthetic hydrocarbon oil, ester oil, silicone oil, fluorine-containing oil, and polyether oil.

  A variety of synthetic greases have the advantages of high and low temperature, load capacity, oxidation resistance, medium resistance, high speed, and radiation resistance due to the use of synthetic oils, and therefore lubricate in aviation, aerospace and various civil equipment.

Grease composition-thickener thickener classification

  Hydrocarbon base: such as ozokerite, paraffin wax, petroleum grease, etc.

  Soap base: the largest one at present, there are sodium base, calcium base, composite calcium, lithium base, composite lithium, barium base, aluminum base, composite aluminum, etc.

  Organic: urea compounds, amide compounds, organic dyes, fluorocarbon compounds, etc.

  Inorganic: bentonite, silica gel, nitrogen boride, graphite, etc.