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Silicone is indeed a magical material, which combines the advantages of organic and inorganic non-metallic materials based on
the element silicon, so some people also call it "the harmony of the piano and the serpent" - the perfect combination of glass and organic materials. After more than 100 years of development, the production process of basic silicone raw materials has become very mature, and domestic enterprises are developing rapidly. A large number of silicone production enterprises like the spring development, to withstand the impact of foreign enterprises.
Now the most common production process of silicone is as follows: the most basic raw materials are three kinds: silicon metal, methanol and hydrogen chloride, none of which is anything special, among which silicon metal is extracted from silicon dioxide, and most of the price is reflected in fuel and electricity. First, let methanol and hydrogen chloride react to produce chloromethane (CH3Cl), then let silicon and chloromethane reaction, the main products obtained are methyltrichlorosilane (Si CH3Cl3), dimethyl dichlorosilane (Si (CH3) 2Cl2), trimethyl chlorosilane (Si (CH3) 3Cl) and tetrachlorosilane (Si Cl4).
Trimethylchlorosilane is called M unit, it has only one reactive group, and the other three methyl groups (or other alkyl groups) are not reactive, so it is often used on both sides of the silicone chain to be a capping agent.
Dimethyl dichloro silane is called D unit, it has two reactive groups, it can help to extend the siloxane chain to both sides, so it can be a chain extender; it can also be linked at the beginning and end by itself to form a ring.
With 4 D linked at the beginning and end, this is octamethylcyclotetrasiloxane (D4), the most famous and most used intermediate in raw materials of silicones. And so on, 5 Ds are D5, 6 Ds are D6.
Sometimes manufacturers are too lazy to separate each of them and sell the ring mixture directly to the downstream, which is DMC.
The one with M at both ends and n D in the middle is dimethylsilicone oil, meaning both ends are methyl capped silicone oil. Dimethyl silicone oil, also called polydimethylsiloxane (PDMS), is used in a variety of lubricating materials, high viscosity, ultra-high viscosity dimethyl silicone oil can also be used in shampoos, sealants, etc.
Methyltrichlorosilane, T-unit, which has three reactive groups, so it can help to form a three-dimensional spatial network structure and make hard silicone resin.
M, D and T are all hydrolyzed to produce silanols first and then they are fractionated out by the difference in boiling points. But so far we have mentioned only three of them as useful, and there are many by-products present in the lower boiling fraction than them or in the higher boiling fraction. The so-called high boilers are impurities with boiling points higher than M, D and T. This includes something called methylhydrodichlorosilane, which when hydrolyzed produces a hydrogen-containing silicone oil.
The side chain of dimethylsilane is all methyl, which is not reactive, while the side chain of hydrogen-containing silicone oil has active hydrogen, which makes it reactive. Therefore, hydrogen-containing silicone fluids are widely used in applications such as: fabric finishing, release agents, powder treatment, and are used to be processed into more complex silicones. The production of hydrogen-containing silicone oil is a good thing to turn waste into treasure.
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