The nature and presentation of room temperature vulcanized silicone rubber

Room temperature vulcanized silicone rubber (RTV) yes the the the the advent of by the the sixties the one kinds of's new type of organic silicon elastomer, the this kind of rubber the most significantly the characteristics of yes under the at room temperature no need to heating, such as pressure you can in-place curing, the use of is extremely convenient. Therefore, an advent of fast become an important component of the silicone products. RTV silicone rubber is widely used as adhesives, sealants, protective coatings, potting and molding materials, has its use in all walks of life.

 

RTV silicone rubber due to the lower molecular weight, known as the liquid silicone rubber, its physical form is usually a flow of fluid or viscous paste, the viscosity of between 100 to 1000000 centistokes. Depending on the requirements, before vulcanization of rubber dubbed automatic leveling perfusion material or not flowing but can be painted scraping the putty. Filler and high-temperature vulcanized silicone rubber room temperature vulcanizing silicone rubber used is similar to silica reinforced vulcanized rubber with 10 to 60 kg / cm 2 tensile strength. Fill in plus that the the different additives can make the glue material has a different the proportion of, hardness, strength, liquidity and thixotropy, as well as the so that vulcanization glue to has the the flame-retardant, conductive, thermal conductivity, resistance to ablation and so on a variety of special performance.

 

RTV silicone rubber according to the packaging can be divided into one-and two-component room temperature vulcanizing silicone rubber, the curing mechanism can be divided into condensation type and molding. Therefore, 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 RTV silicone rubber molding two-component RTV silicone rubber .

 

Single component and two-component condensation RTV silicone rubber, raw rubber alpha of ω-dihydroxy polysiloxane; and molding RTV silicone rubber containing alkenyl and hydrogen side groups (or end groups) polysiloxane, because in the aging, often slightly higher than room temperature (50 ~ 150 ° C) can achieve good curing effect, therefore, also known as low-temperature vulcanizing silicone rubber (LTV).


Three series RTV silicone rubber has its own advantages and disadvantages:

 

Single-- component room temperature vulcanization the the the advantages of of the Silastic is to use the convenient, but the deep the Ministry of curing speed is the more difficult; the the advantages of of the dual-component room temperature vulcanized Silastic yes to and hold hot O'clock the curing, the shrinkage rate is very small, do not expansion, no within the stress, curing can be both internal and surface, can be deep sulfide; molding RTV silicone rubber vulcanization time depends on temperature, therefore, the use of temperature regulation can control the curing rate.

 

One-component RTV silicone rubber

 

Single component room temperature vulcanizing silicone rubber vulcanization reaction is caused by moisture in the air to. Commonly used crosslinking agent is methyl acetoxy silane, Si-OC bond is susceptible to hydrolysis, the acetyl oxygen and water hydrogen-based acetic acid, water, hydroxyl moved to the original acetoxy position, three hydroxy methyl silane. Three hydroxy methyl silane is very unstable and easy to-end-hydroxy linear silicone condensation cross-linked structure. In peacetime, the silanol end group containing silicone raw rubber and fillers, catalysts, crosslinking agents a variety with the agent in a sealed hose, the use of extrusion by the container, by means of moisture in the air and vulcanized into elastomer, release of low molecular weight compounds. Crosslinking agent methyl triacetyl silane silanes containing alkoxy, oxime, amine, amide, keto. Emit the alcohol When the the after the chain is cross-with the alkoxy, known as the de-alcohol type single-- component room temperature to vulcanization the Silastic, When the the after the chain is cross-with the oxime group and, generate the oxime, to referred to as the the deoximation type at room temperature vulcanization Silastic, and Thus, with the to cross-chain agent, one-component RTV silicone rubber to to deacidification type deoximation type, alcohol type, removing the amine type, removing the amide type and de-ketone type many varieties, but the the deacidification type is the most widely used one kinds. Single component room temperature vulcanizing silicone rubber vulcanization time depends on the curing system, temperature, humidity and the thickness of the silicone rubber layer to improve the environmental temperature and humidity can make the curing process to speed up. In the the under the of the a typical the environmental conditions, after general 15 ~ 30 minutes, the the surface of of the Silastic can there is no viscosity, the thickness of .3 cm of the adhesive layer in the the within one day can curing. Curing depth and intensity in the three weeks or so will be gradually increased. Rubber Technology Network

 

One-component RTV silicone rubber with excellent electrical properties and chemical inertness, as well as heat resistance, resistance to natural aging, resistance to flame, moisture, breathable performance. They long-term flexibility in the range of -60 ~ 200 ℃. Curing does not absorb heat, and hold heat, small shrinkage after curing, the adhesion of the material. Therefore, the mainly used as adhesives and sealants, other applications also includes the in-place molding gaskets, protective coatings and caulking materials, and and so on. Many single-component silicone rubber adhesive formulations showed a variety of materials such as most metals, glass, ceramics and concrete auto-adhesive properties, such as bare aluminum, the shear strength of up to 200 pounds / inch 2, the tear strength of up to 20 lbs ft / inch 2 (0.35 joules / cm 2). The When the O'clock the bonding difficulties, the can be, in the its on the substrate, carried out primer to improve the bonding strength, primer can yes the with the reactive silane monomer or resin, When the the they after the curing of the on the substrate, to generate a layer of modified of the suitable for the surface of the silicone adhesive.


One-component RTV silicone rubber is easy to use, but due to its sulfide is restricted according to the lazy atmosphere in the water, so that the thickness of the vulcanized rubber can only be used to require less than 6 mm thickness occasions.

 

Single-- component room temperature yes carried out from gradually Wang Shenchu ​​part of the surface by the vulcanized Silastic of the vulcanization reaction, the adhesive layer is the more thick, the curing is the slower the. When deep but also fast curing, can be layered water gradually curing method, each time to add some plastic material, such as sulfide and then feeding, thus reducing the total curing time. Add magnesium oxide can be accelerated deep glue vulcanization. Two-component condensation RTV silicone rubber two-component condensation RTV silicone rubber is the most common form of RTV silicone rubber, raw rubber is usually a hydroxyl terminated polydimethylsiloxane, with other chelating agent, the catalyst phase together to form a plastic material, this plastic material viscosity range from between 100 centistokes to one million centistokes.

 

Two-component room temperature vulcanized silicone rubber vulcanization reaction does not depend on the moisture in the air, but by the catalyst to trigger. Usually silicone rubber, fillers, crosslinking agent as a component packaging, the catalyst alone as another component of the packaging, or using other combinations, but must be packaged separately from the catalyst and crosslinking agent. Regardless of packaging, began to occur only when the two components are thoroughly mixed together when curing. Commonly used crosslinking agent TEOS and the catalyst is dibutyltin dilaurate. And according to the nature of the final product required by adding appropriate fillers and additives. In recent years, many countries because of dibutyltin dilaurate is moderately toxic levels of substances prohibited in the food bag and plasma bag by adding dibutyltin has been largely replaced by the low toxicity of octyl tin.

 

The condensation of two-component room temperature vulcanized silicone rubber vulcanization time depends on the type, dosage, and temperature of the catalyst. Catalyst amount, the more the faster curing, while leaving aside the shorter the time. At room temperature, set aside time in general for a few hours to set aside time for extension of the plastic material, available cooling. Two-component condensation at room temperature vulcanizing silicone rafters plastic at room temperature to achieve full curing time to take a day or so, but the temperature of 150 ° C only takes one hour. Synergistic effect by using the accelerator γ-aminopropyl triethoxysilane, can significantly improve the cure speed. Two-component RTV silicone rubber to maintain flexibility in the temperature range of 65 ~ 250 ° C for a long time, and has excellent electrical properties and chemical stability, the ability of water, ozone resistance, resistance to weathering, coupled with the use of simple technology applicability Therefore, widely used as a potting and molding materials. A variety of electronic and electrical components at room temperature vulcanizing silicone rubber coating, potting, you can play the role of moisture (corrosion, shock protection and can improve performance and stability parameters of two-component RTV silicone rubber is particularly suitable to do the deep irrigation The seal materials and has a faster vulcanization time, This is point is that superior to Shan component room temperature vulcanized the of the Department of the Silastic.