Organosilicon compounds refer to compounds containing Si-C bonds and at least one organic group directly connected with silicon atoms. In general, organosilicon compounds which are connected with silicon atoms through oxygen, sulfur and nitrogen are also used as organosilicon compounds.


Polysiloxane, which is composed of silicon oxygen bond (-si-0-si-) as skeleton, is the most widely used and the most widely studied one, accounting for more than 90% of the total amount.


Silicone materials have unique structure:


(1) The high energy polysiloxane main chain is shielded by the sufficient methyl on Si atom;


(2) C-H has no polarity, which makes the interaction between molecules very weak;


(3) The Si-O bond is long and the angle of Si-O-Si bond is large.


(4) Si-O bond is a covalent bond with 50% ion bond (covalent bond has directivity and ionic bond has no directivity).


Because of its unique structure, organosilicon also has the properties of inorganic and organic materials. It has the basic properties of low surface tension, low viscosity temperature coefficient, high compressibility and high gas permeability, and excellent properties such as high and low temperature, electrical insulation, oxidation resistance, weather resistance, fire resistance, hydrophobic, corrosion resistance, non-toxic and tasteless, physiological inertia, etc, It is widely used in aerospace, electronic and electrical, construction, transportation, chemical industry, textile, food, light industry, medical and other industries, of which silicone is mainly used in sealing, bonding, lubrication, coating, surface activity, demoulding, defoaming, anti foam, waterproof, moisture-proof, inert filling, etc.


With the continuous growth of organosilicon quantity and varieties, the application field has been widened, forming an important product system which is unique in the new chemical materials field. Many varieties are irreplaceable and indispensable for other chemicals.


Organosilicon materials can be classified into silane coupling agents (organosilicon chemical reagents), silicone oil (silicone grease, silicone emulsion, silicon surfactant), high temperature vulcanized silicone rubber, liquid silicone rubber, silicone resin, composite material and so on.


Silicone rubber


Silicone rubber is a kind of high molecular weight polysiloxane with a direct chain, and its molecular weight is generally over 150000. Its structure is similar to that of silicone oil.


According to the organic groups linked on silicon atoms, silicone rubber has many kinds, such as dimethylsilicone rubber, methyl vinyl silicone rubber, methylphenylsilicone rubber, fluorosilicone rubber, nitrile silicone rubber, ethyl silicone rubber ethyl phenylene silicone rubber and so on.


According to the different curing methods, silicone rubber can be divided into two categories: high temperature vulcanization (hot vulcanization) silicone rubber and room temperature vulcanization (including low temperature vulcanization) silicone rubber.


No matter which type of silicone rubber, no heat release occurs during vulcanization.


High temperature vulcanized silicone rubber is a high molecular weight polysiloxane (the molecular weight is generally 400000-800000), the room temperature vulcanized silicone rubber has a low molecular weight (30000-60000), and has one or two functional groups at both ends of the molecular chain (sometimes in the middle). Under certain conditions (water in the air or appropriate catalyst), these functional groups can react, Thus, the crosslinking structure of high molecular weight is formed.


According to the vulcanization mechanism, room temperature vulcanized silicone rubber can be divided into condensation type and addition molding; According to its packaging method, it can be divided into two types: two components and one component.


The properties of the silicon oxygen bond which constitute the main chain of silicone rubber decide that silicone rubber has the advantages not possessed by natural rubber and other rubber. It has the widest operating temperature range (-100-350oc), excellent high and low temperature resistance. In addition, it also has excellent thermal stability, electrical insulation, weather resistance, ozone resistance, air permeability, high transparency and tear strength, Excellent heat dissipation, excellent adhesion, fluidity and demoulding property. Some special silicone rubber also has excellent oil resistance, solvent resistance, radiation resistance and use at ultra high and low temperature.


In the range of temperature, silicone rubber can not only maintain certain softness, resilience and surface hardness, but also have no obvious change in mechanical properties, but also can resist long-term thermal aging.


Because of the special properties of silicone rubber, it can be used for molding high voltage edge and other electronic components, which makes the adhesive have excellent resistance to leakage and mark, and good demoulding property;


It is used for production of TV, computer, copier, etc. with good heat dissipation and insulation performance.


It is also used as molding gasket, packaging material of electronic parts and protective material of automobile electrical parts which require weather resistance and durability.


Silicone rubber can be used for building and repair of houses, highway joint sealing and caulking seal of reservoir and bridge. Silicone rubber can also be used for strong adhesion, weathering resistance, alkali resistance and water resistant coating.


Because of the high temperature resistance of silicone rubber, it is used in the manufacture of automobile parts.


In addition, there are special purpose silicone rubber, such as conductive silicone rubber, medical silicone rubber, foam silicone rubber, molding silicone rubber.