Organic silicon, or organic silicon compounds are those containing a Si-O bond, and at least one organic base is directly connected with the silicon atom compound, used often to those who have passed on the oxygen, sulfur, nitrogen and silicon atoms of organic base The compounds are also connected as the organic silicon compounds. Among them, the silicon-oxygen bond (-Si-0-Si-) for the skeleton, consisting of polysiloxane, is the largest number of organic silicon compounds to study the deepest, the most widely used class of about 90% of the total amount of .
Structure
Organic silicon material has a unique structure:
(1) Si atoms will be plenty of high-energy methyl polysiloxane main chain shielding;
(2) CH polarity, the interaction between molecules is very weak;
(3) Si-O bond length is longer, Si-O-Si bond angles large.
(4) Si-O bond is a 50% ionic bond covalent bond characteristics (covalent bond is directional, non-directional ionic bonds).
Performance
Because the unique structure of organic silicon, both inorganic and organic materials, performance materials, with a low surface tension, viscosity-temperature coefficient, high compression, high gas permeability of the basic nature, and has high temperature resistance, electrical insulation, resistance to oxidation stability resistance, weather resistance, flame retardant, water-repellent, corrosion-resistant, non-toxic and tasteless, and physical inertia and other outstanding features, widely used in aerospace, electrical and electronics, construction, transport, chemicals, textiles, food, light industry, medical industry, which silicone is mainly used in sealing, bonding, lubrication, coatings, surfactants, mold release, anti-foaming, defoaming, waterproof, moisture-proof, inert fill and so on. As the number and variety of organic silicon growth, applications continue to broaden, the formation of new chemical materials sector, an important product unique system of many species can not be replaced by other chemicals, but essential.
Silicone materials according to their different forms, can be divided into: silane coupling agent (silicone chemical reagents), silicone oil (silicone grease, silicone emulsion, silicone surface active agent), high temperature vulcanized silicone rubber, liquid silicone rubber, silicone , composite materials and so on.
Temperature characteristics
Organic silicon is silicon - oxygen (Si-O) bond-based chain structure, C-C bond energy is 82.6 kcal / mole, Si-O bond in silicone for 121 kcal / mole, so the organic silicon products, high thermal stability, high temperature (or radiation) molecular bond is not broken, do not break down. Silicone not only temperature, but also low temperature, in a wide temperature range. Both physical and mechanical properties or chemical properties, with temperature changes are small.
Weather
Organic silicon's main chain-Si-O-, unparalleled key exists, it can not easily be decomposed by UV light and ozone. Silicone polymer material better than other thermal stability and resistance to radiation and weathering capabilities. Silicone in the life of the natural environment of up to several decades.
Electrical insulation
Silicone products have good electrical insulation, dielectric loss, resistance, voltage, resistance, arc resistance, corona, volume resistivity and surface resistivity of insulating materials are on the top, and their electrical properties by the temperature and frequency little effect. Therefore, they are a stable electrical insulation materials, and is widely used in electronics, electrical industry. Silicone has excellent heat resistance in addition to, but also has excellent water repellency, which is electrical equipment in wet conditions, using highly reliable protection.
Physical inertia
Polysiloxane compounds are known to most non-active compounds in one. They are extremely resistant to biological aging, and animals without rejection, and has better anti-clotting properties.
Low surface tension and low surface energy
Organic silicon's main chain is very soft, the force between the molecules is much weaker than the hydrocarbons, thus, molecular weight hydrocarbons than with low viscosity and surface tension of the weak, the surface energy is small, film-forming ability. This low surface tension and low surface energy is the main reason it received many applications: hydrophobic, anti-foaming, foam stability, anti-sticking, lubrication, polishing and other excellent performance.
The use of silicone
Since silicone has excellent performance of these, so it's wide range of applications. It is not only as aviation, advanced technology, military technology departments to use special materials, but also for national economic sectors, has expanded its scope of application to: construction, electrical and electronic, textile, automobile, machinery, leather, paper, chemical light , metal and paint, pharmaceutical and medical.
Classification of organic silicon
About RTV silicone rubber
RTV silicone rubber (RTV) is the sixties advent of a new type of silicone elastomer, the rubber of the most notable feature is at room temperature without heating, such as local pressure can be cured, extremely easy to use. Thus, came on fast become the silicone products is an important part. RTV silicone rubber is now widely used as adhesives, sealants, protective coatings, potting and molding materials, in all walks of life has its purpose.
Classification
RTV silicone rubber according to their packaging can be divided into one-and two-component room temperature vulcanized silicone rubber, according to the type of curing mechanism can be divided into condensation forming and processing. Therefore, by RTV silicone rubber composition, curing mechanism and the use of technology can be divided into three types, namely, one-component RTV silicone rubber, two-component condensation-type RTV silicone rubber and two-component RTV silicone rubber molding plus . These three series of room temperature vulcanized silicone rubber has its own characteristics: one-component RTV silicone rubber has the advantage of easy to use, but more difficult deep curing rate; two-component RTV silicone rubber has the advantage of curing and hold heat, shrinkage is very small, not expansion, no stress, curing and surface at the same time internal, you can deep sulfide; plus RTV molding silicone rubber vulcanization time depends mainly on temperature, therefore, the use of temperature regulation can control the cure rate .
One-component RTV silicone rubber
Single-component RTV silicone rubber vulcanized by reaction with moisture in the air play a role in the vulcanized into the elastomer. One-component RTV silicone rubber for deacidification type Oxime type, alcohol type, de amine, amide-and off-one off-type and many other varieties. Single-component RTV silicone rubber vulcanization time depends on curing system, temperature, humidity and the thickness of silicone rubber to improve the environmental temperature and humidity, can accelerate the curing process. In a typical environmental conditions, generally 15 to 30 minutes, the silicone rubber surface can not sticky, adhesive layer thickness of 0.3 cm can be cured in one day. Curing depth and intensity in three weeks or so will be gradually enhanced.
One-component RTV silicone rubber with excellent electrical properties and chemical inertness, and heat resistance, natural aging, flame resistance, moisture, permeability and other properties. They range -60 ~ 200 ℃ to maintain long-term flexibility. It does not cure endothermic, hold heat, curing shrinkage, good adhesion of the material. Therefore, mainly used for adhesives and sealants, other applications include in situ forming gaskets, protective coatings and caulking materials. Many single-component silicone rubber adhesive formulations exhibit a variety of materials such as most metals, glass, ceramics and concrete on the auto-adhesive properties. When the bonding difficulties, progress in the substrate primer to improve bonding strength, primer can be a reactive silane monomer or resin, when they are cured on the substrate, for generating a layer of modified silicone adhesive surface. One-component RTV silicone rubber although easy to use, but because it is by curing lazy moisture in the atmosphere, the thickness of the vulcanized rubber is limited, only the thickness of 6 mm for the needs of the occasion. Single-component RTV silicone rubber vulcanization reaction is carried out from the depth of the surface gradually, layer thicker, the slower the cure. When the deep but also fast-curing, the curing method can be stratified water gradually, each time adding some plastic material, such as curing and then feeding, thus reducing the total curing time. Magnesium can be added to accelerate the deep rubber vulcanization.
Two-component condensation-type RTV silicone rubber
Two-component RTV silicone rubber curing reaction does not depend on moisture in the air, but to be triggered by the catalyst. Usually the plastic material and catalyst, respectively, as a component of packaging. Only when the two components are mixed together only when completely cures. Two-component condensation-type RTV silicone rubber vulcanization time depends on the type of catalyst, the amount and temperature. Sulfide catalyst, the more the faster, while leaving aside the shorter the time. At room temperature, the time usually set aside a few hours, to set aside time to extend the rubber, available cooling methods. Two-component condensation-type RTV silicone rubber in the rafters to achieve full cure at room temperature for a day or so, but only 150 ℃ temperature 1 hour. By using the synergistic effect of promoting agents can significantly improve the cure rate.
Two-component RTV silicone rubber available in a 65 ~ 250 ℃ temperature range of long-term flexibility, and has excellent electrical properties and chemical stability, the ability of water resistance, ozone resistance, weather aging, combined with the use of simple, process applicability , therefore, widely used as a potting and molding materials. A variety of electronic, electrical components with RTV silicone rubber coating, potting, you can play the moisture (corrosion, shock and other protection. Can improve performance and stability parameters two-component RTV silicone rubber is particularly suitable for filling in deep do sealing material and has a faster curing time, and this is better than the one-component RTV silicone rubber of the Department. two-component room temperature vulcanized silicone rubber after curing has excellent anti-sticking properties, coupled with minimal shrinkage when cured, Therefore, suitable for the manufacture of soft tooling for casting epoxy resin, polyester resin, polystyrene, polyurethane, vinyl, wax, low melting point alloy mold. In addition, the use of two-component RTV silicone rubber The high simulation performance can be replicated in a variety of exquisite artifacts patterns. two-component room temperature vulcanized silicone rubber should be used Note: First the rubber and catalyst were weighed and mixed in proportion. mixing process should be careful to so attached to the gas volume to a minimum. rubber mixing (uniform color), by standing or vacuum to remove air bubbles, until all air bubbles after discharge, at room temperature or at specified temperature for a certain time that is vulcanized into the silicon rubber.
Plus two-component RTV silicone rubber molding
Plus two-component RTV silicone rubber molding silicone gel and elastic silicone rubber points, the former intensity is low, which is higher than before. Their curing mechanism is based on the silicone gum on the vinyl end groups (or propylene) and cross-linking agent molecules occurs on the addition reaction of silicon-based hydrogen (hydrogen silicide reaction) to complete. In this reaction, do not release by-products. As the cross-linking process does not release low molecular weight material, so plus RTV silicone rubber molding During the curing process does not produce contraction. This type of vulcanized rubber non-toxic, high mechanical strength, excellent hydrolytic stability (even under high-pressure steam), a good low compression set, low flammability, may be the depth of curing, and curing speed can be used to control temperature advantages, at home and abroad to develop a class of silicone rubber.
Plus RTV silicone rubber molding
Packaging is generally points A, B for packaging two components: the catalyst as a component; cross-linking agent for another component. Plus high-strength RTV silicone rubber molding line as low shrinkage, curing does not release low molecular weight, thus molding the fine material. In the machinery industry has been widely used to mold to cast epoxy resin, polyester resin, polyurethane, polystyrene, vinyl plastic, wax, low melting point alloy, concrete upper. Plus-temperature curing molding stifled the use of
Silica gel
This soft rubber vulcanized became transparent silicone gel, can be - 65 ~ 200 ℃ temperature range of long-term flexibility, it has excellent electrical properties and chemical stability, water resistance, ozone resistance, weather aging, water-repellent , moisture, shock, corrosion, and has a physiological inert, non-toxic, odorless, easy pouring, curing can be deep, linear shrinkage rate, easy operation, silicone gel is widely used in the electronics industry electronic components moisture, insulation coating and potting materials, electronic components and assemblies from dust, moisture, vibration and insulation protection. Such as the use of transparent gel encapsulation of electronic components, not only can play a shockproof waterproof protection, but also you can see components and can be detected with a probe component failure, replacement, damage to the silicone gel can be re-potting repair. Because silicone gel high purity, easy to use, has a certain flexibility, it is an ideal transistors and integrated circuits within the coating material, can improve the passing rate of semiconductor devices and reliability; silicone gel can also be used as a flexible adhesive optical instruments. In the medical silicone gel can be used as the body's organs such as the planting of artificial breasts, etc., and used to repair damaged organs.
Silicone
Silicone Silicone is a highly cross-linked polysiloxane network structure, usually with methyl trichlorosilane, dimethyl dichlorosilane, phenyl trichlorosilane, diphenyl dichlorosilane or methyl various mixtures of phenyl dichlorosilane in the presence of organic solvents such as toluene, at a lower temperature hydrolysis, acid hydrolysis has been. The initial hydrolysis product is circular, linear and crosslinked polymer mixture, usually containing a considerable number of hydroxyl groups. After washing to remove acid hydrolysis, neutral body of the initial condensation thermal oxidation in air or in the presence of a catalyst to further condensation, and finally the formation of highly cross-linked three-dimensional network structure. Silicone resin is a thermoset plastic, it is one of the most outstanding performance excellent thermal oxidation stability. 250 ℃ heating for 24 hours, silicone weight loss of only 2 to 8%. Silicone is another outstanding performance, excellent electrical insulation properties, its wide temperature and frequency range are able to maintain its good insulation properties. In view of the above characteristics, mainly as a silicone resin insulating paint (including varnish, enamel, paint, varnish, etc.) impregnated with H-class motor and transformer coils, and for impregnated glass cloth, glass and stone Busi motor cover made of cotton pipe, ele
