Compared with general-purpose rubber, silicone rubber has a relatively simple compounding component of all three types of silicone rubber, as well as a hot-vulcanized type. In addition to raw rubber, the compounding agent mainly includes a reinforcing agent, a vulcanizing agent and some special auxiliaries, and generally only needs 5 to 6 components to form a practical formula. The silicone rubber formulation design should take into account the following points.
(1) Silicone rubber is a high-saturation raw rubber, which is usually not vulcanizable with sulfur, but is heat vulcanized. Thermal vulcanization uses organic peroxides as vulcanizing agents. Therefore, the rubber compounds must not contain active substances that can interact with the decomposition products of peroxides, otherwise they will affect vulcanization.
(2) Silicone rubber products are generally used at high temperatures, and the compounding agent should be stable at high temperatures. For this reason, inorganic oxides are usually used as reinforcing agents.
(3) Silicone rubber can easily cause cracking and rearrangement of siloxane bonds under the action of a trace amount of polar chemicals such as acid or alkali, resulting in a decrease in heat resistance of silicone rubber. Therefore, it is necessary to consider them when selecting compounding agents. The acidity and alkalinity should also take into account the acidity of the peroxide decomposition products so as not to affect the properties of the vulcanizate.
(1) Selection of raw rubber
When designing the formula, the raw rubber with different characteristics should be selected according to the performance and use conditions of the product. For general silicone rubber products, the temperature is in the range of -70 ° C ~ 250 ° C, vinyl silicone rubber can be used; when the product temperature requirements are high (-90 ~ 300 ° C), low phenyl silicon can be used
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