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Composition and structure of grease

Issuing time:2021-05-07 07:30

Do you know what grease is made of Do you really know what grease is?What is lubricating oil? Grease is composed of different soaps mixed with the right amount of lubricating oil according to its use. It can be vividly understood as a sponge filled with lubricating oil.

Many users will confuse grease with lubricating oil, in fact, they are very different. Lubricating oil is generally composed of base oil and additive. Base oil is the main component of lubricating oil, which determines the basic performance of lubricating oil.


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Lubricating oil = base oil + additives (oil liquid flow) -- large fluidity, wide distribution area, uniform, permeability, low adhesion, thin oil film, low resistance. Additives can make up for and improve the performance of the base oil, give some new properties, is an important part of lubricating oil. Grease, on the other hand, can withstand extreme pressure and high impact, maintains good lubrication and adhesion, but has the potential to create resistance.

Lubricating grease is a kind of non-Newtonian fluid lubricant which is obtained by dispersing one or more thickeners in one or more liquid lubricants and is between semi-fluid and solid.

Grease has a certain type, easy to adhere, less fluid than the corresponding base oil.

Grease is mainly composed of thickener, base oil, additive 3 parts: the thickener in the grease to form such as spongy or honeycombed structure skeleton, make it into a paste material; The function of additive is to improve the performance of a certain aspect of grease; The base oil is the dispersion medium in the grease dispersion system, which directly affects the lubricity, evaporation, low temperature and the compatibility with sealing materials of the grease. The performance of grease mainly depends on the composition and structure of the grease, the structure and performance of different components of the grease is different. Generally, the content of thickener in grease is about 2% ~ 30%, the content of base oil is about 70% ~ 98%, and the content of additives and fillers is less than 5%.


1.Base oil

Base oil has a great impact on the performance of grease, including mineral oil and refined oil two categories. At present, the vast majority of grease is mineral oil as the base oil, including paraffin base oil, intermediate base oil and naphthenic base oil and other different hydrocarbon composition of mineral oil. Grease commonly used more moderate viscosity and high viscosity oil, lubricating oil as base oil, there are also some in order to adapt to work under harsh conditions of the need of mechanical lubrication and sealing, adopts the synthetic lubricating oil as base oil, the synthetic oil such as polyether ester synthetic oil, synthetic hydrocarbon oil, all kinds of polysiloxane synthetic oil, containing fluorine synthetic oil, etc.

2.additive

Additives in grease accounted for about 10% is a substance that can improve some performance of grease. According to the performance requirements of grease, can add structure improvement agent, antioxidant, metal passivating agent, rust inhibitor, extreme pressure agent, oil agent, anti-wear agent, adhesive, wire drawing agent, dyeing agent, etc.

Additives can be divided into two categories: one is unique to grease, called glue solvent, which makes the combination of oil and soap more stable, such as glycerol and water, calcium based grease once the loss of water, its structure is completely destroyed, can not be grease, such as glycerol in sodium based grease can adjust the consistency of grease;

The other type of additive is the same as in lubricating oil, such as antioxidant, anti-wear and anti-rust agent, but the amount is generally greater than that in lubricating oil.

Sometimes in order to improve the resistance of grease flow and enhance the ability of lubrication, often add some graphite, disulfide key and carbon black as filler.

3.thickener

Thickener is an important component of grease. Thickener is dispersed in the base oil and forms a spatial network structure of grease, which can adsorb and fix the base oil. It determines the mechanical stability of grease, high temperature resistance, colloidal stability and water resistance, etc. There are two main classes of thickeners used in preparing greases. Soap based thickeners (i.e., fatty acid metal salts) and non-soap based thickeners (hydrocarbon, inorganic, and organic).

Soap-based thickeners are salts formed by the chemical reaction of fats or fatty acids with bases. The soap-based raw materials used for soap-making include natural fats such as butter, lard, cottonseed oil, rapeseed oil and castor oil, as well as single-component fatty acids such as stearic acid, dodecyl hydroxyl stearic acid, palmic acid and oleic acid after processing, while the alkali is mainly lithium hydroxide, calcium hydroxide and barium hydroxide. Because aluminum hydroxide belongs to amphoteric hydroxide, it can not react directly with fatty acids, so the use of aluminum isopropanol or triisopropoxy trioxy aluminum instead.

Soap thickener can also be divided into three kinds: simple saponyl (such as calcium-based fat), mixed soap (such as calcium-based fat) and complex soap (such as complex calcium-based fat). The metal salt made of high and low fatty acids, high and diacid is the complex soap. About 90% of greases are now made with soap-based thickeners. Non-soap-based thickeners can be divided into organic and inorganic thickeners. Polyurea, fluorine resin, terephthalate and phthalocyanine dye are the main organic thickening agents. Inorganic thickening agents include bentonite, silica gel, etc.

4.Production process and technology

This step is the most important step in grease, with good technology and saponification process will completely change the quality of grease. And the rough process and simple technology to produce grease is no problem to the naked eye, but if the use of the process, then the performance of the working effect will be a world of difference, China high quality grease and high performance grease manufacturer, supplier, factory products to be competitive.

The consistency level of grease and the corresponding working penetration degree. Consistency of lubricating oils (grease only, not lubricating oils) - International method for measuring consistency at 25 ° C using ASTM D217 test method. Fill a circular vessel with the same amount of grease, and then insert a long needle in the shape of a cone into the depth of the grease with the same pressure for five consecutive times. Then average out the numbers.

NLGI= Consistency = American Institute of Lubrication and Grease. Consistency is equal to the shape and hardness of the grease, but does not indicate its viscosity. NLGI Grease Conversion Classification (National Grease Institute, NLGI) Assembly oil or gear oil with no. 00, 0, 1, 2, and the most appropriate is the consistency of 0/1/2 grease.

The above is the basic information and composition of grease.