（1） keep the processing process clean, can not be mixed with other rubber, oil or impurities, otherwise it will affect the vulcanization and performance of silicone rubber;
（2）Silicone rubber products need to be cured by hot air for a long time in the oven to improve the properties of the vulcanized rubber.

mixed

Silicone rubber raw rubber is soft, has a certain plasticity, and can be mixed directly by open mixer or internal mixer without plasticizing. Mixing methods can be as follows:

(1) open mixer mixing
The speed ratio of the double roll mill is (1.2 ~ 1.4) ∶1, the fast roll is behind, the higher speed ratio leads to faster mixing, and the low speed ratio can make the film smooth. The roller must be provided with cooling water, and the mixing temperature should be below 40℃ to prevent scorching or volatilization loss of vulcanizing agent. At the beginning of mixing, the roll distance is small (1 ~ 5mm), and then gradually increases.

Feeding and operation sequence: raw rubber (roll)- reinforcing filler - structure control agent - heat-resistant additives - colorant - thin pass 5 times - blanking, oven heat treatment - back refining - curing agent - thin pass - park overnight - back refining - sheet. The adhesive material can not be heat treated by oven, after adding heat-resistant additives, adding vulcanizing agent and then thin-tong, parking overnight back to smelting, and then parking for a few days back to smelting out pieces for use. Mixing time was 20-40min.

(2) Mixing by internal mixer
Mixing time is 6 ~ 16min with laboratory 2L internal mixer. There is no special difficulty in mixing. When the charging coefficient is 0.74, mixing can be carried out normally with Φ160mm open mixer. The discharging temperature is related to the type of reinforcing filler. When weak reinforcing filler and precipitation method silica are used, the discharging temperature is below 50℃. When using the gas phase method of white carbon black, the discharge temperature is about 70℃.

Squeeze out
Silicone rubber is generally soft, good extrusion effect, easy to operate, can extrude a variety of different shapes and sizes of products, its processing equipment and tools are basically similar to ordinary rubber. Extruder is generally used Φ30 or A 65mm single thread screw, length to diameter ratio of (10 ~ 12)∶1 effect is better. When extruding, keep low temperature as far as possible, preferably no more than 40℃, so the cylinder and screw must be supplied with cooling water. For the products with higher quality requirements, 80 ~ 140 mesh filter can be installed near the machine head to remove the impurities in the rubber material and improve the extruding quality.

Silicone rubber extruded semi-products are soft and easily deformed, so they must be vulcanized immediately. The most common method is hot air continuous vulcanization; Wire and cable industries usually use high pressure steam continuous vulcanization. If it cannot be vulcanized continuously after extrusion, in order to prevent deformation, it should be taken immediately after extrusion by disc, drum or conveyor belt, and isolated with talcum powder to avoid mutual bonding. If it is found that the rubber material is too soft for extrusion, 3 ~ 5 parts of gaseous silica can be mixed into the rubber material.