Causes: due to the high water permeability of silicone rubber, especially the compound made of precipitated silica, the moisture content in the compound increases linearly with the increase of relative humidity in the air. When there is too much water, the silicone rubber changes from transparent to opaque. Especially in winter, due to the low ambient temperature, the water release time on the rubber surface is very slow or can not be released at all, resulting in easy bubbles on the surface of extruded products. General precipitated silica is not suitable as silicone rubber filler for extrusion molding due to its high water content.

Solution: the surface of white carbon black can be treated with alkoxysilane to change its hydrophilic surface into hydrophobic surface and reduce the water absorption of the rubber; High temperature treatment can also reduce the water absorption of rubber, so as to improve the bubble problem of extruded rubber.

At present, in the production of extruded rubber, in the existing formula system, the 2# structure control agent can be replaced with diethyloxysilane to better treat the surface moisture of white carbon black. Of course, pay attention to safety in the production process. In the process, the first step of rubber mixing by gas phase method can be adopted. After the rubber is cold refined, Place it in the 30 ~ 40 ℃ curing room for curing treatment for about 8 hours, then vacuum heat treat the rubber, and strictly control the effective mixing time and temperature of the rubber, that is, the mixing time and temperature of the rubber in the high temperature section, so as to improve the bubble problem of the extruded rubber.