Silicone Rubber (SiliconeRubber) is a kind of polymer elastic material with both inorganic and organic properties. Its molecular main chain is composed of silicon atoms and oxygen atoms (—Si—O—Si—). Hydrocarbon or substituted hydrocarbon organic groups, such groups can be methyl, unsaturated vinyl (molar fraction generally does not exceed 01005) or other organic groups, this low degree of unsaturated molecular structure makes silicone rubber It has excellent heat aging resistance and weathering resistance, and is resistant to ultraviolet and ozone erosion. The molecular chain has large flexibility and weak interaction between molecular chains. These structural features make the vulcanizate soft and elastic, but the physical properties are poor.

 

 

Silicone rubber was developed in the 1940s. The earliest foreign species studied was dimethyl silicone rubber. Around 1944, the company was put into production by the American DowCorning Company and GeneralElectric Company. China successfully researched and put it into industrial production in the early 1960s. At present, in addition to our foreign countries producing silicone rubber, there are more than 1,000 varieties and brands in the United States, Britain, Japan, the former Soviet Union and Germany.

 

 

Application

 

 

Silicone rubber has unique comprehensive properties, especially the biocompatibility of silicone rubber is a key characteristic. It has been successfully used in other places where rubber is ineffective, and it has solved many technical problems and satisfied modern industry and The needs of everyday life. Like other rubbers, silicone rubber can be processed into various profiles, silicone tubes, silicone strips, silicone rubber rollers, silicone cloths and other silicone products; room temperature vulcanized silicone rubber can be applied on a large area on site and is easy to use.

 

 

 

(1) Automotive industry

 

 

 

The application of silicone rubber in the automotive industry is growing rapidly. Silicone rubber (especially silicone rubber with various characteristics) can withstand the erosion of fuel oil and lubricants, improve the performance of automobile parts, and reduce maintenance costs. Can be used in automotive ignition wires, spark plug protective covers, heating and radiator hoses, muffler linings, battery connectors, and fuel pumps made of fluorosilicone rubber. With the development of the electrification of vehicle electronics, room temperature vulcanized silicone rubber is widely used in electronic components, potting materials for electrical assemblies, windshield glass, car body seals and reflectors.

 

 

 

(2) Electronics and electrical industry

 

 

 

The electronics and electrical industries are one of the earliest and most demanding areas of silicone rubber as an insulating material. Silicone rubber is mainly used in TV anode cover, high voltage protective cover, high voltage lead-out wire, refrigerator defroster wire, power or signal transmission wire and cable, etc. Insulators made of silicone rubber will be widely used in power transmission lines instead of ceramic products, especially ultra-high-voltage lines.

 

 

Conductive silicone rubber is used for electrical contacts and liquid crystal display contacts of electronic computers, telephones and other instruments. Wires and cables made of flame-retardant and radiation-resistant silicone rubber are widely used in nuclear power stations. Silicone rubber heating sheet and heating belt are used to control the working temperature of various precision instruments and oil pipelines, and are used as heating blankets for physiotherapy thermal applicators in medical treatment. Room temperature vulcanized silicone rubber can be used as a potting material for waterproofing, dampproofing and shockproofing.

 

 

 

Silicone rubber has been widely used in pump seals of dishwashers and washing machines due to its heat-resistant washing liquid performance. Silicone rubber is ideal for use as a gasket on appliances such as coffee pots, electric fryers, and steam irons. The earphones and head pads of the stereo headphones are changed to silicone rubber, which can eliminate external noise and is soft and comfortable.

 

 

 

(3) Aerospace Industry

 

 

 

Silicone rubber is an indispensable high-performance material in the aerospace industry. It can withstand the ultra-cold space and the heat returned to the atmosphere, extend the life of aircraft parts, reduce maintenance costs, and reduce accidents. Mainly used in aircraft body cavity seals, electrical connectors, sealed switches, dust and waterproof covers, gasket gaskets, "O" seal rings for jet engines and hydraulics, oxygen masks, regulating diaphragms, hot air ducts, and Radar wireless shock absorber, etc. Burn-resistant silicone rubber is suitable for coating rocket fuel valves, power source cables, and rocket launch manhole covers to prevent burns from rocket jets. Room temperature vulcanized silicone rubber can be used as air-tight seal, window frame seal, shock-proof and moisture-proof potting material.

 

 

 

(4) Construction industry

 

 

 

Silicone rubber has good weather resistance and workability. As an adhesive sealant, it has been widely used in the construction industry, surpassing other types of sealants. In recent years, a low-modulus, high-elongation two-component sealant has also been developed, which is used for large-scale components such as concrete prefabricated parts with large joint movements and curtain walls. Room temperature vulcanized silicone rubber is also used for sealing joints of asbestos cement boards, sealing of bathroom tile joints and toilet appliances. With the decline of rubber prices in the future, the scope of applications will be further expanded, such as replacing asphalt and neoprene in the application of highway joints. High-temperature vulcanized silicone rubber sponge strips are used as sealing strips for doors and windows of buildings.

 

 

(5) Medical field

 

 

 

Silicone rubber has good biocompatibility, small response to the body, stable performance, low hemagglutination, can withstand high temperature and pressure multiple cooking, and can be processed into products of various shapes, such as silicone film, silicone sponge, silicone Balloon is the most widely used material in medicine.

 

 

(6) Other fields

 

 

 

In addition to the above-mentioned applications, the application of silicone rubber in textiles, printing, machinery, plastics, chemical, papermaking, food and cosmetics has also increased significantly. Typical products are rolls made of silicone rubber, used for heat setting, embossing, calendering and fixing of copiers for fabrics and plastics. Air-conditioned windows made of silicone rubber films have been used to store fruit and vegetables. In addition, silicone rubber has also achieved good results as a sealing material in textile high-temperature equipment and equipment with high concentrations of alkali, sodium hypochlorite and hydrogen peroxide.

 

 

新 New progress in the research of silicone rubber

 

 

 

Silicone rubber has excellent high and low temperature resistance, ozone resistance, oxygen resistance, light resistance and weathering resistance, excellent electrical insulation properties, special surface properties and physiological inertia, and high air permeability, and has a wide range of applications. However, the tensile strength and tear strength of silicone rubber are relatively low, the acid and alkali resistance are poor, and the processing performance is also poor when manufacturing complex products. In recent years, many countries around the world have carried out many improvements to this end and achieved some results .

 

 

(1) A new polymer (blend) is obtained by copolymerizing (blending) the silicone with other monomers or polymers. For example, a block copolymer of silicone and polycarbonate can be used as a selective breathable membrane; the characteristics of a blend of silicone and ethylene-propylene rubber are between silicone rubber and ethylene-propylene rubber; blending silicone rubber with EVA, The prepared blend has excellent physical properties, electrical properties, high temperature aging resistance and heat shrinkage properties, and can be endowed with excellent flame retardancy properties through proper blending. The use of high-temperature resistant silicone rubber and high tensile strength PMMA to manufacture interpenetrating polymer grids, which improves the strength of silicone rubber and the heat resistance of PMMA. By synthesizing polydimethylsiloxane (PDMS) / polystyrene (PS) interpenetrating polymer network, which improves the mechanical and elastic properties of the silicone network.

 

 

(2) By improving the matching technology, we have developed new varieties of high specificity such as high strength, high tear resistance and low compression deformation, as well as high temperature resistance, ultra low temperature resistance, flame resistance, heat conduction and heat shrinkable silicone rubber.

 

 

Pure silicone rubber products do not have the mechanical strength required for most applications and therefore need to be reinforced. The traditional strengthening method is to add reinforcing fillers before curing the silicone rubber, and then carry out mixing, vulcanization and other processes. However, it is time-consuming, energy-consuming, pollutes the environment, and it is difficult to control the degree of dispersion and aggregation of the filler in the rubber compound. Studies show that fillers such as precipitated silica, precipitated titanium dioxide and ferrite, zeolite, and alumina have a better reinforcing effect on silicone rubber.

 

 

 

(3) In terms of improving the processability, we have developed two-stage vulcanized silicone rubber, granular silicone rubber (also known as powder rubber), and a catalytic addition between vinyl-containing polysiloxane and hydrogen-containing siloxane. In response, a silicone rubber liquid injection molding system was developed. Additive two-component system is used to develop a putty-type silicone rubber with good thixotropy, excellent construction performance and easy to use.