With the development of the silicone industry, the application of silicone rubber is becoming more and more extensive. Compared with traditional rubber, silicone rubber has excellent characteristics such as aging resistance, weather resistance, low toxicity, odorless, flame retardant, and recyclability. Like traditional rubber, silicone rubber also needs to be strengthened by adding structural reinforcing agents before it can be more widely used. Commonly used silicone rubber structural reinforcing agents are silica, silicone resin, etc. Generally, the surface of silica without hydrophobic treatment has a large number of free hydroxyl groups, and it is easy to form hydrogen bonds with the organic silicon raw rubber molecules, resulting in the rapid structure of the compounded rubber over time, which seriously affects the processing of downstream product factories. Therefore, in the mixing process of raw rubber and white carbon black and other auxiliary materials, it is necessary to add a structuring control agent to reduce the structuring or delay the structuring time. Commonly used structural control agents are alkoxysilanes, low molecular weight hydroxy silicone oils, and methoxy silicone oils.

Methoxysilicone oil is a new type of structural control agent, which is a high molecular polymer obtained by the chain extension reaction of methoxysilane and organosilicon ring. Methoxysilicone oil is a polymer, its molecular weight is several times higher than that of methoxysilane, and its flash point is >60°C. It is a Class C common chemical, while methoxysilane is a small molecule compound with a low flash point and is a hazardous chemical. Methoxy silicone oil has methoxy reactive groups like methoxysilane.

Methoxysilicone oil works on the same principle as methoxysilane for structural control. The reactive methoxy group reacts with the free hydroxyl groups on the surface of silica to generate methanol under heating conditions, thereby eliminating the free hydroxyl groups on the surface of silica and controlling the structure of the mixed rubber. The generated methanol is easily volatilized from the compounded rubber, so that the rubber compound remains dry, stiff, and has good mold release properties. The general principle of small molecular hydroxy silicone oil as a structural control agent is to condense with the hydroxyl group on the surface of silica at high temperature to form water molecules, which is difficult to discharge from the rubber compound in time. If the dosage is too large, it is easy to cause the rubber to become sticky, stick to the stick in the downstream product process, and difficult to demold. If the water molecules are not completely discharged, it will also cause the mixed rubber to fog, affecting the transparency and other problems.

The rubber compound treated with methoxy silicone oil is obviously drier than the rubber compound treated with hydroxy silicone oil, the rubber compound is stiff and the transparency is better, and the performance of the rubber compound treated with methoxysilane is similar. The structural control effect of methoxy silicone oil alone is not as good as that of hydroxy silicone oil, which is consistent with the activity of methoxy silicone oil being inferior to that of hydroxy silicone oil. The mixed use of methoxy silicone oil and hydroxy silicone oil can achieve good results in all indicators.

Methoxy silicone oil mixed with hydroxy silicone can significantly improve the feel, transparency and mold release properties of the rubber compound while maintaining the anti-structural properties. Generally, under the constant ratio of the total amount of hydroxy silicone oil, methoxy silicone oil can be used to partially replace hydroxy silicone oil. If it is a methoxysilane formulation system, it can also be directly replaced with methoxysilicone oil. Methoxysilicone oil is much safer than methoxysilane, but since some methanol is generated during the production of silica treated with methoxysilicone oil, the rubber compound is drier and easy to accumulate static electricity. In the dry season, it is best to discharge the methanol produced by nitrogen or vacuum to avoid safety accidents caused by static electricity.