Thermal vulcanized silicone rubber is a kind of silicone product with large output and wide application. Silicone rubber has excellent high and low temperature resistance. It can be used for a long time in the range of - 60~250 ℃. It also has excellent electrical insulation performance, ozone resistance, weather aging resistance, water repellency, moisture resistance, and good physiological inertia.

Add reinforcing filler, vulcanizing agent (or not) and other additives to the hot vulcanized silicone rubber raw rubber, and the rubber can be mixed to form a rubber mix. The rubber can be processed into various silicone rubber products by general rubber processing methods such as molding and extrusion.

Generally, the silicone rubber can be mixed in the general rubber open mill, and large-scale production is carried out in the kneader or closed mixing equipment.

Detailed description of each process:

1. Mixing:
When the open mill is used for mixing (rarely used), it is better to equip dust prevention or air extraction device above the open mill roller to reduce the flying of white carbon black. No other impurities or rubber particles shall be mixed in the mixing process, the temperature shall be controlled below 40 ℃, and sufficient cooling water shall be opened. The open mill mixes and eats powder slowly, and the mixing time of each batch of rubber is about 20~40min. Mixing with internal mixer can not only improve production efficiency and reduce labor intensity, but also reduce the flying of white carbon black and improve the operating environment.

2. Heat treatment:
When the fumed silica without surface modification is used as the reinforcing agent, the structure control agent must be added to the rubber compound. Therefore, the heat treatment of rubber has become a necessary process. The purpose of heat treatment is to further combine the structure control agent with the surface of white carbon black (Si-OH) and eliminate the low molecular volatile matter in the gum. The general conditions of heat treatment are: under nitrogen protection or in the kneader with reduced pressure, treat at 160 ℃~200 ℃ for 1~1.5h.

3. Filter:
For extruded products, calendered products, gelatinized products and diaphragm products, mechanical impurities and undispersed particles of the compounding agent are one of the main factors leading to product quality problems. Therefore, the rubber used for the above products must be filtered. Rubber filter or ordinary extruder can be used for filtering. The temperature of barrel and screw shall be controlled to the minimum, and the specification of filter screen shall be 120~200 meshes.

4. Refining:
After the rubber is parked, it must be re refined when it is used because the gel content increases and the plasticity decreases. The re refining of rubber should be limited, and the re refining is insufficient, the rubber has poor flexibility, and the surface is uneven; However, if the re refining is excessive, the rubber surface will become sticky, which is not conducive to operation.

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