Application of fumed silica in silicone rubber products.silicone bibs uk custom

source:silicone plate manufacturers release time:2022-07-13

　　It is generally known that the threshold of food-grade silicone products has reached the level of contact with human skin and daily products, but it is unclear why there is a difference between ordinary silicone materials and food-grade silicone materials, and even higher-end medical-grade silicone raw materials are Differentiate, then today I will explain to our friends what kind of material food-grade silica gel is, and it is different from ordinary silica gel!

　　The materials of many common silica gel products in life are derived from ordinary silica gel materials, and the chemical material components are derived from the definite method silica, also known as the definite method silica gel. A variety of compounds can not meet the testing standards, such as FDA, ROHS, LFGB testing certification, and food-grade silicone will not appear white when stretched, and the stretch can reach about 500%. The silicon dioxide obtained by burning silicon tetrachloride and air has a fineness of more than 1000 mesh. The precipitation method is to use sodium silicate to add sulfuric acid to precipitate the silicon dioxide. The fineness is only 300-400 mesh. Therefore, the price of fumed silica gel is obviously higher than that of ordinary silica gel in terms of performance.

　　Food-grade silica gel, referred to as fumed silica in raw materials, is synthesized from polymer microparticle compound materials, with good fluidity, high specific gravity, and stronger surface adsorption capacity. It is relatively high and has better dispersion performance, so it has an advantage in various properties of silicone products. With its superior stability, reinforcement, thickening and thixotropy, it has unique characteristics in many disciplines and fields. , has an irreplaceable role.

　　Influence of fumed silica on mechanical properties of HTV silicone rubber

　　The reinforcement of fumed silica to HTV silicone rubber is affected by its particle size, comparative area and structure. Generally, the smaller the particle size, the higher the specific surface area, the higher the structure, and the better the reinforcement effect. The higher the strength and hardness. In addition, the amount of fumed silica and its dispersion in the matrix have a great influence on the performance of the vulcanizate. There are also many reinforcement mechanisms and models of fumed silica for silicone rubber. The more recognized explanation is that The free hydroxyl groups on the surface of fumed silica form a physical or chemical bond with the silicone rubber molecules, and a silicone rubber molecular adsorption layer is formed on the surface of the silica to form a three-dimensional network structure in which the fumed silica and the silicone rubber molecules are integrated, so as to effectively Limit the deformation of the molecular chain of silicone rubber and strengthen it. The change of tear strength of vulcanizate is similar to that of tensile strength, both of which increase with the improvement of the reinforcement of fumed silica, first increase with the increase of the amount of fumed silica, and then decrease slightly after reaching the peak value.

　　The effect of fumed silica on the processing properties of HTV silicone rubber products is generally expressed in terms of the degree of structure (? Crepe), Crepe is equal to the plasticity value (p28) of the mixed rubber after being stored at room temperature for 28 days and measured immediately after mixing The difference in plasticity value (P0), the plasticity value of the compound is related to the amount of fumed silica, surface properties and structure. The reason for the structure is that the surface hydroxyl groups of fumed silica form hydrogen bonds with the oxygen atoms in the silicone rubber and the surface of the silica adsorbs the molecular chains of the silicone rubber. The material becomes hard and affects the processing performance.

　　Therefore, it is necessary to add a structure control agent or select surface-treated fumed silica during use. The addition of structure control agent and the surface treatment of fumed silica are all controlled by structure control machine or surface treatment agent and silica. The silanol groups on the surface react, thereby reducing the number of surface hydroxyl groups, reducing the number of hydrogen bonds formed with the silicone rubber, shortening the mixing time of the rubber compound, increasing the plasticity, reducing the structuring effect, and improving the processing performance and storage stability. the goal of.

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