Silica gel
Open categories: silicone rubber, silica gel, fine-porous silica gel, inorganic silica gel, silica gel desiccant
Basic information
Name : Silicone
Alias: Silicone rubber
English name: Silicon dioxide
English alias: Silica gel; Silica
Molecular formula: H2O3Si
Molecular weight: 60.08
CAS registration number: 7631-86-9
EINECS registration number: 231-545-4
Word explanation : Chemical formula xsio 2·yh 2o. Transparent or milky white granular solid. It has an open porous structure, strong adsorption, and can adsorb a variety of substances. If it absorbs water, the moisture absorption capacity is about 40%. If cobalt chloride is added, it will turn blue when dry and red after absorbing water. Renewable and reusable.
Generally speaking, silica gel can be divided into two categories: organic silica gel and inorganic silica gel according to its properties and components.
Inorganic silica gel is a highly active adsorption material. It is usually produced by reacting sodium silicate and sulfuric acid and undergoing a series of post-treatment processes such as aging and acid bubbles. Silica gel is an amorphous material, and its chemical molecular formula is mSiO2. nH2O. It is insoluble in water and any solvent, non-toxic, tasteless, chemically stable, and does not react with any substances except strong alkali and hydrofluoric acid. Various types of silica gel form different microporous structures due to different manufacturing methods. The chemical composition and physical structure of silica gel determine that it has many characteristics that are difficult to replace by other similar materials: high adsorption performance, good thermal stability, stable chemical properties, high mechanical strength, etc.
Silica gel is divided into macroporous silica gel, coarse pore silica gel, B-type silica gel and fine pore silica gel according to its pore size. Due to different pore structures, their adsorption properties have different characteristics. Coarse-pore silica gel has a higher adsorption capacity when the relative humidity is high, while fine-pore silica gel has a higher adsorption capacity than coarse-pore silica gel when the relative humidity is low. Type B silica gel has a pore structure between coarse and fine. Between the pores, the adsorption capacity is also between coarse and fine pores. Macroporous silica gel is generally used as catalyst carrier, matting agent, toothpaste abrasive, etc. Therefore, different varieties should be selected according to different uses.
Safety performance
The main component of silica gel is silica, which is chemically stable and does not burn. Silica gel is a kind of amorphous silica. The dust content in the workshop should be controlled to no more than 10 mg/cubic meter. Exhaust ventilation needs to be strengthened and a mask should be worn during operation.
Silica gel has strong adsorption capacity and can have a drying effect on human skin. Therefore, work clothes should be worn during operation. If silicone gets into your eyes, rinse with plenty of water and seek medical treatment as soon as possible.
Blue silica gel contains a small amount of cobalt chloride, which is toxic. You should avoid contact with food and inhalation. If poisoning occurs, you should seek medical treatment immediately.
During use, silica gel absorbs water vapor or other organic substances in the medium, and its adsorption capacity decreases. It can be reused after regeneration.
1. Regeneration after silica gel absorbs water vapor
After silica gel absorbs water, it can be removed through thermal desorption. There are many heating methods, such as electric furnaces , flue waste heat heating and hot air drying, etc.
The temperature of desorption heat is preferably controlled at 120--180°C. For blue gel indicators, color-changing silica gel, and DL-type blue silica gel, it is appropriate to control it at 100--120°C. The maximum temperature during regeneration of various industrial silica gels should not exceed the following limits:
Coarse-pore silica gel shall not be higher than 600°C;
Fine-pore silica gel shall not be higher than 200°C;
The blue gel indicator agent (or color-changing silica gel) shall not be higher than 120℃;
The silica-aluminum gel shall not be higher than 350℃.
The moisture content of regenerated silica gel can generally be controlled below 2 before it can be put back into use.
2. Regeneration of silica gel after adsorbing organic impurities
1. Roasting method
For coarse-porous silica gel, it can be placed in a roasting furnace and gradually heated to 500-- 600℃, about 6-8 hours until the colloidal particles turn white or yellowish brown. For fine-porous silica gel, the baking temperature cannot exceed 200°C.
2. Rinse method
Adsorb the silica gel in saturated water vapor until it is saturated, then soak it in hot water and rinse it. Detergent can be used in combination to remove waste oil or other organic impurities, and then After washing with clean water, dry and dehydrate.
⒊ Solvent flushing method
According to the type of organic matter adsorbed by the silica gel, an appropriate solvent is selected to dissolve the organic matter adsorbed in the silica gel, and then the silica gel is heated to remove the solvent.
3. Issues that should be paid attention to when regenerating silica gel
1. When drying and regenerating, attention should be paid to gradually increasing the temperature to avoid violent drying that will cause the rubber particles to burst and reduce the recovery rate.
2. When silica gel is roasted and regenerated, excessive temperature will cause changes in the pore structure of the silica gel, significantly reducing its adsorption effect and affecting its use value. For blue gel indicators or color-changing silica gel, the desorption and regeneration temperature should not exceed 120°C, otherwise the color development effect will be lost due to the gradual oxidation of the color developer.
⒊ The regenerated silica gel should generally be screened to remove fine particles to make the particles uniform.
Storage and Packaging
Silica gel has strong moisture absorption capacity, so it should be stored in a dry place with a shelf between the packaging and the ground. Packaging materials include steel drums, paper drums, cartons, plastic bottles, polyethylene plastic composite bags, flexible container bags, etc. Rain, moisture and exposure to the sun should be avoided during transportation. Shandong Xinhua Silica Gel: www.xinxuchem.com
Organic Silica Gel
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The basic structural unit of organic silica gel products is composed of silicon-oxygen It is composed of chain links, and the side chains are connected to various other organic groups through silicon atoms. Therefore, the structure of silicone products contains both "organic groups" and "inorganic structures". This special composition and molecular structure allows it to combine the characteristics of organic substances and the functions of inorganic substances. Compared with other polymer materials, the most outstanding properties of silicone products are:
1. Temperature resistance properties
Organic silicone products have a main chain structure of silicon-oxygen (Si-O) bonds. The bond energy of C-C bonds is 82.6 kcal/gram molecule. The bond energy in silicone is 121 kcal/gram molecule, so silicone products have high thermal stability, and the chemical bonds of molecules will not break or decompose under high temperatures (or radiation exposure). Silicone is not only resistant to high temperatures, but also to low temperatures and can be used in a wide temperature range. Whether it is chemical properties or physical and mechanical properties, the changes with temperature are very small.
2． Weather resistance
The main chain of silicone products is -Si-O-, and there are no double bonds, so it is not easily decomposed by ultraviolet light and ozone. Silicone has better thermal stability, radiation resistance and weather resistance than other polymer materials. The service life of silicone in the natural environment can reach decades.
3. Electrical insulation properties
Organic silicone products have good electrical insulation properties, and their dielectric loss, voltage resistance, arc resistance, corona resistance, volume resistivity and surface resistivity are among the best among insulating materials. , and their electrical properties are little affected by temperature and frequency. Therefore, they are stable electrical insulating materials and are widely used in the electronic and electrical industries. In addition to excellent heat resistance, silicone also has excellent water repellency, which guarantees the high reliability of electrical equipment when used in wet conditions.
4. Physiologically Inert
Polysiloxanes are among the most inactive compounds known. They are very resistant to biological aging, have no rejection reaction with animal bodies, and have good anticoagulant properties.
5. Low surface tension and low surface energy
The main chain of silicone is very flexible, and its intermolecular force is much weaker than that of hydrocarbons. Therefore, it has a lower viscosity than hydrocarbons of the same molecular weight, and its surface The tension is weak, the surface energy is small, and the film-forming ability is strong. This low surface tension and low surface energy are the main reasons why it has many applications: hydrophobic, defoaming, foam stabilization, anti-sticking, lubrication, glazing and other excellent properties.
2. Uses of organic silicon
Because organic silicon has the above-mentioned 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, textiles, automobiles, machinery, leather and papermaking, chemical and light industry, Metal and paint, medicine and medical treatment, etc.
3. Classification of organic silicone
Organic silicone is mainly divided into three categories: silicone rubber, silicone resin and silicone oil.
IV. Classification of silicone rubber
Silicone rubber is mainly divided into room temperature vulcanized silicone rubber and high temperature vulcanized silicone rubber
Introduction and classification of room temperature vulcanized silicone rubber
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Room temperature vulcanized silicone rubber (RTV) is a new type of silicone elastomer that came out in the 1960s. The most significant feature of this rubber is that it can be cured in place at room temperature without heating or pressing. It can be used Extremely convenient. Therefore, it quickly became an important part of the entire silicone products as soon as it came out. Room temperature vulcanized silicone rubber is now widely used as adhesives, sealants, protective coatings, potting and molding materials, and has its uses in various industries.
Room temperature vulcanized silicone rubber can be divided into single-component and two-component room temperature vulcanized silicone rubber according to its packaging method. According to the vulcanization mechanism, it can be divided into condensation type and addition type. Therefore, room temperature vulcanized silicone rubber can be divided into three major types according to different compositions, vulcanization mechanisms and usage processes, namely single-component room temperature vulcanized silicone rubber, two-component condensation type room temperature vulcanized silicone rubber and two-component addition type room temperature vulcanized silicone rubber. . Each of these three series of room temperature vulcanized silicone rubber has its own characteristics: the advantage of one-component room temperature vulcanized silicone rubber is that it is easy to use, but the deep curing speed is difficult; the advantage of two-component room temperature vulcanized silicone rubber is that it does not release heat during curing. The shrinkage rate is very small, there is no expansion, and there is no internal stress. The curing can be carried out both internally and on the surface at the same time, and can be deeply vulcanized. The vulcanization time of addition type room temperature vulcanization silicone rubber mainly depends on the temperature. Therefore, the vulcanization speed can be controlled by adjusting the temperature. .
Among the many synthetic rubbers, silicone rubber is the best. It is odorless and non-toxic, not afraid of high temperatures and resistant to severe cold. It is "calm" and "face unchanged" at 300 degrees Celsius and minus 90 degrees Celsius, and still retains its original strength and elasticity. Silicone rubber also has good electrical insulation, oxygen resistance and anti-aging properties, light resistance and anti-aging properties, mildew resistance, chemical stability, etc. Due to these excellent properties, silicone rubber has been widely used in modern medicine. In recent years, hospitals, scientific research institutions and factories have collaborated to successfully trial-produce a variety of silicone rubber medical supplies.
Silicone rubber anti-noise earplugs: comfortable to wear, can block noise well and protect eardrums.
Silicone rubber fetal head aspirator: easy to operate, safe to use, can be deformed according to the size of the fetal head, the fetal scalp will not be sucked up during suction, and can avoid scalp hematoma and intracranial injury. Greatly reduce the pain during childbirth for pregnant women with dystocia.
Silicone rubber artificial blood vessel: It has special physiological functions and can be "intimate" with the human body. The human body does not reject it. After a certain period of time, it will become fully stable with human tissue. Extremely good.
Silicone rubber eardrum repair sheet: The sheet is thin and soft, with good smoothness and toughness. It is an ideal material for repairing eardrums, and it is easy to operate and has good results.
In addition, there are silicone rubber artificial trachea, artificial lungs, artificial bones, silicone rubber duodenal tubes, etc., all of which are very effective.
Uses of room temperature vulcanized silicone rubber
With the advancement and development of modern science and technology, the use of silicone rubber in medicine will have broader prospects.
Foam silicone rubber is based on condensed hydroxyl-terminated silica raw rubber, hydroxyl hydrogen-containing silicone oil is the foaming agent, and vinyl platinum complex is the catalyst (heated
Catalyst is dibutyl tin dilaurate), a porous sponge-like elastomer formed by foaming and vulcanization at room temperature. In order to improve the quality of the foam, some other components should be added, such as silicone oil, to produce more gas during the vulcanization process; to improve the feel of the foam and reduce the density. Adding diphenylsilanediol can not only control the foam structure, but also control the viscosity increase during storage. However, the amount should not be too much, otherwise it will affect the electrical properties of the foam. In order to improve the physical and mechanical properties of the foam, transparent silicone rubber can also be added. The amount of vinyl complex of chloroplatinic acid as catalyst should not be too much, subject to the convenience of operation, otherwise the viscosity will increase and it is not conducive to operation; when the amount of catalyst is insufficient, the vulcanization will be incomplete, and the surface of the foam will be sticky and elastic. Good, soft and plastic, poor strength.
Foam silicone rubber is liquid before vulcanization and is suitable for potting materials. The vulcanized foam can be used for a long time at -60~159℃. After aging at 150℃ for 72 hours, or ten times of alternating hot and cold use at -60~1070℃, the foam will still maintain its original properties.
Foam silicone rubber is an ideal material due to its high thermal stability, good thermal insulation, insulation, moisture resistance, and shock resistance, especially at high frequencies. Lightweight encapsulation material. Used in various electronic components, instruments, meters, aircraft instrument wheels, etc., it can play the "three defenses" of "moisture-proof, shock-proof, and anti-corrosion" protection. In addition, it can also be used as a filling material for thermal insulation interlayers and as a floating material in salt spray atmosphere. Materials and sealing materials. Foamed silicone rubber can also be used as filling, repairing and dressing materials in orthopedics.
In order to meet the fire protection requirements of power transmission lines, the American Anti-Corning Company has developed a flame-retardant type. Room temperature vulcanized foam silicone rubber DC3-6548. This foam silicone rubber is mainly used for fire sealing where wires and cables pass through (such as holes in roofs, walls, buildings, etc.). It has very good flame retardant properties and its limiting oxygen index reaches 39 (absolute). The limiting oxygen index of most plastics is only 20) and its service life is as long as 50 years. At present, this kind of flame-retardant room temperature vulcanized foam silicone rubber has been widely used in nuclear power plants, electronic computer centers, offshore oil production equipment and other harsh environmental conditions, or fire protection requirements. Particularly high places.
Introduction to two-component condensation type room temperature vulcanization silicone rubber 2007-05-24 09:09 Two-component condensation type room temperature vulcanization silicone rubber is the most common type of room temperature vulcanization silicone rubber. The raw rubber is usually hydroxyl-terminated polysiloxane, which is combined with other ingredients and catalysts to form a rubber compound. The viscosity of this rubber compound can range from 100 centistokes to one million centistokes.
The vulcanization reaction of two-component room temperature vulcanized silicone rubber is not initiated by moisture in the air, but by a catalyst. Usually, the silicone rubber, filler, and cross-linking agent are packaged as one component, and the catalyst is used alone. Another component is packaged, or other combinations are used, but the catalyst and cross-linking agent must be packaged separately. Regardless of the packaging method used, curing does not begin until the two components are completely mixed together. The chain agent is ethyl orthosilicate, and the catalyst is dibutyltin dilaurate. Appropriate fillers and additives are added according to the properties of the desired final product. In recent years, dibutyltin dilaurate is classified as moderately toxic in many countries. Level substances, dibutyltin is prohibited in food bags and plasma bags, and has been basically replaced by low-toxic octyltin.
The vulcanization time of two-component condensation room temperature vulcanized silicone rubber mainly depends on the catalyst. Type, dosage and temperature. The more catalyst is used, the faster the vulcanization will be, and the shorter the storage time will be at room temperature. If you want to extend the storage time of the rubber, you can use the two-component condensation method. It takes about a day for room temperature vulcanized silicone rafter glue to fully cure at room temperature, but it only takes 1 hour at a temperature of 150°C through the synergistic effect of the accelerator γ-aminopropyltriethoxysilane. Significantly improves its curing speed.
Two-component room temperature vulcanized silicone rubber can maintain elasticity for a long time in a temperature range of 65 to 250°C, has excellent electrical properties and chemical stability, and is resistant to water, ozone, and weather aging. In addition, It is easy to use and has strong process applicability, so it is widely used as potting and molding materials. After coating and potting various electronic and electrical components with room temperature vulcanized silicone rubber, they can protect against moisture (anti-corrosion, shockproof, etc.) and can improve performance and stability parameters. Two-component room temperature vulcanized silicone rubber is particularly suitable for deep potting The sealing material has a faster vulcanization time, which is better than one-component room-temperature vulcanized silicone rubber.
One-component room-temperature vulcanized silicone rubber
Single component. The vulcanization reaction of room temperature vulcanized silicone rubber relies on the interaction with moisture in the air to vulcanize into elastomers. Depending on the chain agent, one-component room temperature vulcanized silicone rubber can be deacidified, deoximated, or dealcoholized. , deamine type, deamidation type and deketone type and many other varieties. The vulcanization time of one-component room temperature vulcanized silicone rubber depends on the vulcanization system, temperature, humidity and thickness of the silicone rubber layer. Increasing the temperature and humidity of the environment can Accelerate the vulcanization process. Under typical environmental conditions, the surface of the silicone rubber can be no longer sticky after 15 to 30 minutes, and the thickness of the 0.3 cm adhesive layer can be cured in about three weeks. Will gradually be enhanced.
One-component room temperature vulcanized silicone rubber has excellent electrical properties and chemical inertness, as well as heat resistance, natural aging resistance, flame resistance, moisture resistance, breathability and other properties. It can maintain elasticity for a long time in the range of 200℃. It does not absorb or release heat when cured, has a small shrinkage after curing, and has good adhesion to materials. Therefore, it is mainly used as an adhesive and sealant. Other applications include. Form-in-place gaskets, protective coatings, caulking materials, etc. Many one-component silicone rubber adhesives are formulated to exhibit self-bonding properties on a variety of materials such as most metals, glass, ceramics, and concrete. When bonding is difficult, a primer can be applied to the base material to improve the bonding strength. The primer can be a reactive silane monomer or resin. When they are cured on the base material, a layer of modified silane monomer or resin is formed. Silicone bonding surface. Although one-component room temperature vulcanized silicone rubber is easy to use, because its vulcanization depends on moisture in the atmosphere, the thickness of the vulcanized rubber is limited and can only be used in situations requiring a thickness of less than 6 mm. The vulcanization reaction of single-component room temperature vulcanized silicone rubber proceeds gradually from the surface to the depth. The thicker the rubber layer, the slower the curing. When the deep layer needs to be cured quickly, the layered pouring stepwise vulcanization method can be used, adding more water each time. Some rubber materials are added after vulcanization, which can reduce the total vulcanization time.
2. Two-component condensation type room temperature vulcanization silicone rubber.
The vulcanization reaction of two-component room temperature vulcanized silicone rubber is not initiated by moisture in the air, but by a catalyst. Usually, the rubber compound and the catalyst are packaged as one component. Only when the two components are completely mixed. Curing begins at the same time. The vulcanization time of two-component condensation type room temperature vulcanized silicone rubber mainly depends on the type, dosage and temperature of the catalyst. The more catalyst used, the faster the vulcanization will be, and the shorter the storage time will be at room temperature. Generally, it takes a few hours. If you want to extend the shelf time of the rubber, you can use the cooling method. It takes about a day for the two-component condensation type room temperature vulcanized silicone rafter glue to be fully cured at room temperature, but it only takes about a day at a temperature of 150°C. It takes 1 hour. Its curing speed can be significantly increased through the use of accelerators for a synergistic effect.
Two-component room temperature vulcanized silicone rubber can maintain elasticity for a long time in a temperature range of 65~250℃, has excellent electrical properties and chemical stability, and is resistant to water, ozone, and weather aging. In addition, It is easy to use and has strong process applicability, so it is widely used as potting and molding materials. After coating and potting various electronic and electrical components with room temperature vulcanized silicone rubber, they can protect against moisture (anti-corrosion, shockproof, etc.) and can improve performance and stability parameters. Two-component room temperature vulcanized silicone rubber is particularly suitable for deep potting Sealing material and has a faster vulcanization time, which is better than single-component room temperature vulcanized silicone rubber.
Two-component room temperature vulcanized silicone rubber has excellent anti-adhesion properties after vulcanization, and its shrinkage rate is extremely small during vulcanization. Therefore, it is suitable for manufacturing soft molds and is used for casting epoxy resin, polyester resin, polystyrene, Molds for polyurethane, vinyl plastics, paraffin, low melting point alloys, etc. In addition, the high simulation performance of two-component room temperature vulcanized silicone rubber can be used to reproduce various exquisite patterns on cultural relics. When using two-component room temperature vulcanized silicone rubber, please note: first, weigh the rubber and catalyst separately, and then mix them in proportion. The mixing process should be done carefully to minimize the amount of trapped gas. After the rubber is mixed (even in color), the bubbles can be removed by leaving it alone or decompressing (vacuum degree 700 mmHg). After all the bubbles are discharged, it can be vulcanized into silicon by placing it at room temperature or at a specified temperature for a certain period of time. rubber.
3. Two-component addition type room temperature vulcanization silicone rubber
Two-component addition type room temperature vulcanization silicone rubber can be divided into elastic silicone gel and silicone rubber. The former has lower strength and the latter has higher strength. Their vulcanization mechanism is based on the addition reaction (hydrosilylation reaction) between the vinyl group (or propylene group) on the end group of the organic silicone rubber and the silicon hydrogen group on the cross-linking agent molecule. In this reaction, no by-products are released. Since no low molecular weight substances are released during the cross-linking process, addition room temperature vulcanized silicone rubber does not shrink during the vulcanization process. This type of vulcanized rubber is non-toxic, has high mechanical strength, has excellent hydrolysis resistance (even under high-pressure steam), good low compression deformation, low flammability, can be deeply vulcanized, and the vulcanization speed can be controlled by temperature, etc. Advantages, so it is a type of silicone rubber currently being vigorously developed at home and abroad. Two-component room temperature vulcanized silicone rubber can maintain elasticity for a long time in the temperature range of 165 to 250°C, and has excellent electrical properties and chemical stability. It is resistant to water, ozone, and weather aging. In addition, it is simple to use and has strong process applicability. , therefore, widely used as potting and molding materials. After coating and potting various electronic and electrical components with room temperature vulcanized silicone rubber, they can protect against moisture (anti-corrosion, shockproof, etc.) and can improve performance and stability parameters. Two-component room temperature vulcanized silicone rubber is particularly suitable for deep potting Sealing material and has a faster vulcanization time, which is better than single-component room temperature vulcanized silicone rubber.
Two-component room temperature vulcanized silicone rubber has excellent anti-stick properties after vulcanization. The shrinkage rate during vulcanization is extremely small, so it is suitable for making soft molds for casting epoxy resin, polyester resin, polystyrene, polyurethane, vinyl plastic, paraffin, low melting point alloy, etc. In addition, it is used. The high simulation performance of two-component room temperature vulcanized silicone rubber can reproduce various exquisite patterns. For example, it can be used to reproduce ancient bronzes in the reproduction of cultural relics, and can be used to reproduce the skin patterns of snakes, pythons, crocodiles, pangolins and other animals in the production of artificial leather. , which has the effect of confusing fakes with real ones.
When using two-component room temperature vulcanized silicone rubber, you should pay attention to several specific issues: first, weigh the base material, cross-linking agent and catalyst separately, and then mix them in proportion. Usually the two components should be provided in different colors so that the mixing of the two components can be visually observed. The mixing process should be carefully operated to minimize the amount of trapped gas. ), the bubbles can be removed by letting it stand or reducing pressure (vacuum level: 700 mmHg). After all the bubbles are discharged, it can be vulcanized into silicone rubber by leaving it at room temperature or at a specified temperature for a certain period of time.
In addition to the methyl group, the side groups on the main chain of the two-component room temperature vulcanized silicone rubber siloxane can be replaced with other groups such as phenyl, trifluoropropyl, cyanoethyl, etc. to improve its low temperature resistance and resistance to Heat resistance, radiation resistance or solvent resistance. At the same time, heat resistance, flame retardant, thermal conductivity, and electrical conductivity additives can be added as needed to produce silicone rubber with ablation resistance, flame retardancy, thermal conductivity, and electrical conductivity. p>
(1) Methyl room temperature vulcanized silicone rubber
Methyl room temperature vulcanized silicone rubber is an old variety of general-purpose silicone rubber. It is water-resistant, ozone-resistant, arc-resistant, corona-resistant and weather-resistant. Aging and other advantages. It can be used in a temperature range of 60 to 200°C. Therefore, it is widely used as a filling and sealing material for electronic and electrical components, and as a moisture-proof, shock-proof, high and low temperature resistant filling and sealing material for instruments.
It can also be used to make molds for casting polyester resin, epoxy resin and low melting point alloy parts. It can also be used as dental impression material. Coating cotton cloth and paper bags with methyl room temperature vulcanized silicone rubber can be used to make conveyor belts and packaging bags for transporting sticky items.
(2) Methyl diphenyl room temperature vulcanized silicone rubber
In addition to the excellent properties of methyl diphenyl room temperature vulcanized silicone rubber, methyl diphenyl room temperature vulcanized silicone rubber is better than A Base room temperature vulcanized silicone rubber has a wider operating temperature range (-100 ~ 250℃). Low phenyl room temperature vulcanized silicone rubber (108-1) with a phenyl content of 2.5 to 5% can maintain elasticity under low temperature conditions of -120°C. It is currently the best low-temperature performance among silicone rubbers; the phenyl content is 10 ~20% room temperature glue (108-2) has good radiation resistance, ablation resistance and self-extinguishing properties. If a certain amount of heat-resistant additives such as Fe2O3 are added to it, the thermal aging performance can be improved, and it is suitable for 250 Used at high temperatures above ℃ or used as ablation-resistant putty coatings and encapsulating materials.
Methyl phenyl room temperature adhesive, like other room temperature adhesives, can be used for dipping, impression and release. If you want to increase the adhesion with other materials, you must perform surface treatment on the adhered material before using the material. The surface treatment steps are as follows: Clean the surface of the material 1 to 2 times with acetone solvent, and then treat it with a surface agent 1 ~2 times, bake in a 60°C oven for a few minutes. At this time, a layer of less sticky film will be formed on the surface of the material, and the glue can be applied.
(3) Methyl block room temperature vulcanization silicone rubber
Methyl block room temperature vulcanization silicone rubber is a modified variety of methyl block room temperature vulcanization silicone rubber. It is sealed by hydroxyl groups. It is a polymer of polydimethylsiloxane (107 glue) and methyltriethoxysilane oligomer (molecular weight 3 to 5). Under the catalysis of dibutyltin dilaurate, the hydroxyl groups in polydimethylsiloxane and the ethoxy groups in polymethyltriethoxysilane are condensed to form a three-dimensional polymer. After vulcanization, the elastic The silicone rubber has higher mechanical strength and adhesive force than methyl room temperature vulcanization silicone rubber, and can be used for a long time in a temperature range of 70 to 200°C.
Methyl block room temperature vulcanized silicone rubber has the properties of shockproof, moisture-proof, waterproof, breathable, ozone resistance, weather aging resistance, and resistance to weak acids and weak alkali. It has good electrical insulation properties, good adhesive properties, and is low cost. Therefore, it can be widely used in potting, coating, impression, demoulding, drug carrier release and other occasions. Electronic components potted with methyl block room temperature adhesive have the functions of shockproof, moisture-proof, sealing, insulation, and stabilization of various parameters. Applying methyl block room temperature glue directly to the speaker can reduce and eliminate the mid-frequency points of the speaker. After vulcanization, the resonant frequency performance of the speaker can be reduced by about 20 Hz. After adding a certain amount of additives to the methyl block room temperature adhesive, it can be used as a paper anti-sticking agent. After applying a thin layer of methyl block room temperature adhesive on the candy and biscuit conveyor belts in the food industry, the anti-stick properties of the canvas can be improved, thereby improving the appearance of the food and increasing the utilization of raw materials.
Add an appropriate amount of fumed silica to the methyl block room temperature adhesive, which can be used to install window glass, curtain walls, window frames, seams of prefabricated panels, and expansion joints of airport runways. In addition, it can also be used as an adhesive for magnetic cores and templates in electronic computer memories, and as an adhesive for conductive silicone rubber and non-conductive silicone rubber. Treating fabrics with methyl block room temperature vulcanized silicone rubber can improve the fabric's feel, softness and bending resistance.
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