Organosilicon chemistry mainly studies the properties and reactivity of organosilicon compounds. Organic silicon compounds are organic compounds containing carbon silicon bonds. Like carbon, organosilicon is a tetra coordinated tetrahedron structure.
In biological molecules, no compounds containing carbon silicon bonds have been found. The first organosilicon compound was jointly discovered by French chemist Friedel C and American chemist Crafts J in 1863.
They reacted with silicon tetrachloride and diethyl zinc to get tetraethyl silicon. The simple carbon silicon compound silicon carbide is an inorganic compound.
Organosilicon is an important part of the new chemical material industry and an important basic material for the development of the seven strategic emerging industries proposed by the State Council. It plays an irreplaceable role in many other chemical materials and is a veritable "industrial vitamin" and "technology catalyst".
Physical structure
1： The organic silicon material has a unique structure:
(1) Sufficient methyl groups on Si atoms shield the main chain of high-energy polysiloxane;
(2) C-H is nonpolar, which makes the intermolecular interaction very weak;
(3) Si-O bond length is longer, and Si-O-Si bond angle is larger.
(4) Si-O bond is a covalent bond with 50% ionic bond characteristics (covalent bond has directionality, ionic bond has no directionality).
2： Performance:
Because of its unique structure, organic silicon has the properties of both inorganic and organic materials, and has the basic properties of low surface tension, low viscosity temperature coefficient, high compressibility, high gas permeability, and other excellent characteristics such as high and low temperature resistance, electrical insulation, oxidation resistance stability, weather resistance, flame retardant, hydrophobic, corrosion resistant, non-toxic, tasteless, and physiological inertia, It is widely used in aerospace, electronic and electrical, construction, transportation, chemical industry, textile, food, light industry, medical and other industries, among which organic silicon is mainly used in sealing, bonding, lubrication, coating, surface activity, demoulding, defoaming, foam suppression, waterproof, moisture-proof, inert filling, etc. With the continuous growth of the quantity and variety of organosilicon, the application field has been continuously expanded, forming a unique important product system in the field of new chemical materials. Many varieties are irreplaceable and essential to other chemicals.
The metabolism of organisms also requires the participation of organosilicon, which is usually expressed as CH3 (SiOH) 3. Organic silicon plays an important role in various functions of the body and is directly related to the absorption of minerals. The average human body has about seven grams of silicon, which is far more than other important minerals, such as iron. Iron and silicon are essential to the human body and play a very important role in maintaining normal metabolism.
Organosilicon materials can be divided into silane coupling agent (organosilicon chemical reagent), bioactive organosilicon, silicone oil (silicone grease, silicone emulsion, silicone surfactant), high-temperature vulcanized silicone rubber, liquid silicone rubber, silicone resin, composite, etc. according to their different forms.
Performance Introduction
The basic structural unit of organic silicon products is composed of silicon oxygen chain links, and the side chains are connected with other organic groups through silicon atoms. Therefore, the structure of organosilicon products contains both "organic groups" and "inorganic structure". This special composition and molecular structure make it integrate the characteristics of organic matter and the functions of inorganic matter. Compared with other polymer materials, the most outstanding properties of silicone products are:
1. Temperature resistance
Organic silicon products are based on the silicon oxygen (Si-O) bond as the main chain structure. The bond energy of the C-C bond is 82.6 kcal/mole, and the bond energy of the Si-O bond in organic silicon is 121 kcal/mole. Therefore, organic silicon products have high thermal stability, and the chemical bond of the molecule does not break or decompose under high temperature (or radiation exposure). Organic silicon can not only withstand high temperature, but also low temperature, and can be used in a wide temperature range. Both chemical properties and physical and mechanical properties change little with temperature.
2. Weather resistance
The main chain of organosilicon products is - Si-O -, and there is no double bond, so it is not easy to be decomposed by ultraviolet light and ozone. Organic silicon has better thermal stability, radiation resistance and weather resistance than other polymer materials. The service life of organic silicon in natural environment can reach several decades.
3. Electrical insulation performance
All organosilicon products have good electrical insulation performance. Their dielectric loss, voltage resistance, arc resistance, corona resistance, volume resistance coefficient and surface resistance coefficient are among the best among insulating materials, and their electrical performance is little affected by temperature and frequency. Therefore, they are stable electrical insulating materials, and are widely used in electronic and electrical industries. In addition to excellent heat resistance, organosilicon also has excellent water repellency, which is the guarantee of high reliability of electrical equipment in wet conditions.
4. Low surface tension and low surface energy
The main chain of organosilicon is very flexible, and its intermolecular force is much weaker than that of hydrocarbons. Therefore, its viscosity is lower than that of hydrocarbons with the same molecular weight, its surface tension is weak, its surface energy is small, and its film forming ability is strong. This low surface tension and low surface energy are the main reasons for its various applications: hydrophobic, defoaming, foam stability, anti sticking, lubrication, polishing and other excellent properties.
Because organosilicon has these excellent properties, its application range is very wide. It is not only used as a special material in aviation, cutting-edge technology and military technology sectors, but also in various sectors of the national economy. Its application scope has expanded to: construction, electronics and electrical, textile, automobile, machinery, leather and paper, chemical and light industry, metal and paint, medicine and medicine, etc.
