Cause: Due to the large water permeability of the silicone rubber, especially the mixing rubber made by the precipitated white carbon black, the moisture content in the rubber compound increases linearly with the increase of the relative humidity in the air. When the moisture is too much, the silicone rubber changes from transparent to opaque, especially in winter. Due to the low ambient temperature, the moisture release time of the rubber surface is slow or not released at all, resulting in easy bubbles on the surface of the extruded product. Generally, the precipitation method of white carbon black is not suitable for the silicone rubber filler for extrusion molding because its water content is too high.
Solution: The surface of silica can be treated with alkoxysilane to transform the hydrophilic surface into a hydrophobic surface, which reduces the water absorption of the rubber. It can also reduce the water absorption of the rubber by high temperature treatment. Improve the bubble problem of the extruded compound. At present, the extrusion compound is in production. In the existing formulation system, the 2# structure control agent can be replaced with diethoxysilane to better treat the surface moisture of the white carbon black, of course, in the process of production. Pay attention to safety. The first step of gas phase mixing can be used in the process. After the rubber is cooled out, it is placed in a 30~40°C health room for about 8 hours, and the rubber is vacuum treated. Strictly control the effective mixing time and mixing temperature of the rubber compound, that is, the mixing time and temperature of the rubber compound in the high temperature section, thereby improving the bubble problem of the extruded rubber compound.