Basic introduction of silica gel materials
Silica gel is a highly active adsorption material, which is an amorphous material. It contains polysiloxane, silicone oil, silica (silica), coupling agent and filler. The main component is silica, and its chemical molecular formula is msio2 · nH2O. Insoluble in water and any solvent, non-toxic and tasteless, stable chemical properties, and does not react with any substance 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 be replaced by other similar materials: high adsorption performance, good thermal stability, stable chemical properties, high mechanical strength and so on.
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Classification of silica gel: silica gel can be divided into thermal vulcanized silicone rubber and room temperature vulcanized silicone rubber according to its vulcanization characteristics. According to different properties and uses, it can be divided into general type, ultra low temperature resistant type, ultra high temperature resistant type, high strength type, oil resistant type, medical type and so on. According to the different monomers used, they can be divided into methyl vinyl silicone rubber, methyl phenyl vinyl silicone rubber, fluorosilicone, * * silicone rubber, etc.
What are the molding conditions from raw rubber to mixed rubber?
1. In the mixing process, due to the low molecular cohesion of silicone rubber, silica filler with high reinforcement and high temperature resistance has become the most important compounding agent of silicone rubber. When selecting other compounding agents, nursery rhymes need to consider the requirements of high temperature resistance, that is, under the application conditions of silicone rubber, they shall not volatilize, decompose, carbonize or change color. In order to maintain the heat resistance of silicone rubber, Reduce the fracture of silicon bond caused by acid and alkali attack. When mixing, prevent foreign acid and alkali from being brought in, and timely remove the acidic substances produced by the decomposition of peroxide vulcanizing agent!
2. When the mixed raw rubber and other ingredients are cooked in a vacuum kneader, the temperature is not high at the beginning. In the process of mixing, the temperature height is slowly increased through friction to 155-160 degrees, and it will take another half an hour. 3. Put the cooked glue into the open mill to grind it into a roll. As long as you don't get dirty, the rolling times only need 2-3 turns. 4. After grinding, cool it for about 3-4 hours, and then filter the glue through the screen in order to filter out some solid materials in the glue.
What are the types and characteristics of silica? There are mainly two methods: gas phase method and precipitation method: gas phase method: most of them start from silicon tetrachloride, mix with chlorine and oxygen (air), and at a high temperature of more than 1000 ℃, hydrogen burns with oxygen to generate water, and then reacts with silicon tetrachloride to generate fine powder. After coalescence, capture and acid removal, white carbon black products are obtained. Advantages of gas phase method: pure height, less SiOH, high reinforcement rate, hot air vulcanization, high transparency of vulcanizate, good electrical performance, excellent sealing, cushion resistance and dynamic fatigue resistance. Application of gas phase method: car parts, wires, cables, medical food, high-strength, high transparent silicone rubber products, resistant gasket and sealing gasket. Precipitation method: starting from water glass, adding hydrochloric acid or sulfuric acid for neutralization reaction under stirring to obtain SiO2 precipitation, which is filtered, dried and ground into white carbon black with high fineness. It can also be obtained from alkaline earth metal silicic acid through acid decomposition reaction. Advantages of precipitation method: vulcanizate has good elasticity, compression permanent deformation, swelling resistance and processing performance, low price, rubber material is not easy to structure, and can only be used for filling and reinforcement of rubber and plastic products. Application of precipitation method: general molding products, rubber rollers, oil resistant gasket materials.
What's the difference between silicone and rubber?
We usually mistakenly think that silica gel is a kind of rubber. In fact, this is wrong. The main components of raw materials of silica gel are extracted from silica (such as silicone oil and white carbon black), while the raw materials of rubber are extracted from resin. The cost of silica gel is more expensive and environmentally friendly than rubber.