Organic silica gel


Organosilicon compounds refer to compounds that contain Si-C bonds and at least one organic group is directly connected to silicon atoms. Traditionally, compounds that connect organic groups to silicon atoms through oxygen, sulfur and nitrogen are also regarded as organosilicon compounds.


Among them, polysiloxane with siloxane bond (- si-0-si -) as skeleton is the most numerous, most deeply studied and most widely used type of silicone compounds, accounting for more than 90% of the total dosage.


Silicone materials have a unique structure:


(1) Sufficient methyl groups on Si atoms shield the high-energy polysiloxane backbone;


(2) C-H is nonpolar, which makes the intermolecular interaction very weak;


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


(4) Si-O bond is a covalent bond with the characteristics of 50% ionic bond (covalent bond has directivity, ionic bond has no directivity).


Due to its unique structure and the properties of both inorganic and organic materials, silicone has the basic properties of low surface tension, small viscosity temperature coefficient, high compressibility and high gas permeability, and has excellent characteristics such as high and low temperature resistance, electrical insulation, oxidation stability, weather resistance, flame resistance, hydrophobicity, corrosion resistance, non-toxic and tasteless, physiological inertia and so on, It is widely used in aerospace, electronic and electrical, construction, transportation, chemical industry, textile, food, light industry, medical and other industries. Silicone 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 is constantly widened, and an important product system unique in the field of new chemical materials is formed. Many varieties are irreplaceable and essential 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 straight chain high molecular weight polysiloxane with a molecular weight of more than 150000. Its structural form is similar to silicone oil.


According to the different organic groups linked on the silicon atom, silicone rubber has many varieties, such as dimethyl silicone rubber, methyl vinyl silicone rubber, methyl phenyl silicone rubber, fluorosilicone rubber, nitrile silicone rubber, ethyl silicone rubber, ethyl phenylene silicone rubber and so on.


According to different vulcanization methods, silicone rubber can be divided into high-temperature vulcanization (thermal vulcanization) silicone rubber and room temperature vulcanization (including low-temperature vulcanization) silicone rubber.


No matter what type of silicone rubber, there is no exothermic phenomenon during vulcanization.


High temperature vulcanized silicone rubber is high molecular weight polysiloxane (molecular weight is generally 400000 ~ 800000). Room temperature vulcanized silicone rubber generally has low molecular weight (30000 ~ 60000). There are one or two functional groups at both ends of the molecular chain (sometimes in the middle). These functional groups can react under certain conditions (moisture in the air or appropriate catalyst), Thus, a high molecular weight crosslinking structure is formed.


Room temperature vulcanized silicone rubber can be divided into condensation type and addition type according to its vulcanization mechanism; According to its packaging method, it can be divided into two-component and single component types.


The properties of the silicone oxygen bond forming the main chain of silicone rubber determine that silicone rubber has the advantages that natural rubber and other rubbers do not have. It has the widest working temperature range (- 100 ~ 350oC) and 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. Some special silicone rubber also has excellent oil resistance, solvent resistance, radiation resistance and use at ultra-high and low temperatures.


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


Due to the special properties of silicone rubber, it can be used for molding high-voltage edge and other electronic components, so that the rubber has excellent resistance to electric leakage and marking and excellent demoulding;


It is used in the production of TV sets, computers, copiers, etc. it has good heat dissipation and insulation performance.


It is also used as molding gasket requiring weather resistance and durability, packaging material for electronic parts and protective material for automotive electrical parts.


Silicone rubber can be used for building and repair of houses, joint sealing of expressways and caulking sealing of reservoirs and bridges. Silicone rubber can also be used for coatings with strong adhesion, weather resistance, alkali resistance and water resistance.


Due to the high temperature resistance of silicone rubber, it is widely used in the production of automobile parts.


In addition, there are special uses of silicone rubber, such as conductive silicone rubber, medical silicone rubber, foam silicone rubber, molding silicone rubber, heat shrinkable silicone rubber and so on.