High temperature vulcanized silicone rubber means that the process of polysiloxane into an elastomer is vulcanized at high temperature (110-170 ° C). It mainly uses high molecular weight polymethyl vinyl siloxane as raw rubber, mixed with reinforcing filler, vulcanizing agent, etc., and vulcanized into elastomer under heating and pressure. The reinforcement of silicone rubber is mainly various types of silica, which can increase the strength of the vulcanizate dozens of times. Sometimes in order to reduce the cost or improve the performance of the rubber compound and give the vulcanized rubber various special properties, various additives are also added. Sulfiding agents are various organic peroxides or addition reaction catalysts.

Raw rubber types and preparation:
The main types of raw rubber are methyl silicone rubber, methyl vinyl silicone rubber, methyl phenyl vinyl silicone rubber and fluorosilicone rubber. In addition, phenylene groups can also be introduced into the main chain. The largest amount is methyl vinyl silicone raw rubber. Due to the introduction of vinyl groups, which are active groups for cross-linking, the cross-linking efficiency of peroxide cross-linking of raw silicone rubber is greatly improved. Almost all commercial silicone rubbers contain some amount of vinyl.

Silicone rubber is mainly produced by alkali-catalyzed polymerization and acid-catalyzed polymerization in industry. More use of KOH and temporary catalysts [(CH3)4NOH, (n-C4H9)4POH].

Processing and forming:
The purpose of the primary vulcanization is to carry out the cross-linking reaction of the polymer chain; the purpose of the secondary vulcanization is to supplement the cross-linking, drive off the decomposition products of the vulcanizing agent and other volatile compounds to stabilize the properties of the vulcanizate. Commonly used equipment are open rubber mixer, kneader and vacuum mixer.

Main performance:
(1) High temperature performance. The remarkable feature of silicone rubber is high temperature stability. Although the strength of silicone rubber at room temperature is only half of that of natural rubber or some synthetic rubbers, it can still maintain a certain degree of flexibility and recovery at high temperatures above 200 °C. Elasticity and surface hardness, and no significant change in mechanical properties. (2) Low temperature performance The glass transition temperature of silicone rubber is generally -70~-50 °C, and the special formula can reach -100 °C, indicating that its low temperature performance is excellent. This is of great significance to the aviation and aerospace industries. (3) The Si-O-Si bond in weather-resistant silicone rubber is very stable to oxygen, ozone and ultraviolet rays, and has excellent weather resistance without any additives. (4) Electrical properties. Silicone rubber has excellent insulating properties, corona resistance and arc resistance are also very good. (5) Physical and mechanical properties. The physical and mechanical properties of silicone rubber at room temperature are worse than that of general-purpose rubber, but at a high temperature of 150 °C and a low temperature of -50 °C, its physical and mechanical properties are better than general-purpose rubber. (6) Resistance to oil and chemical reagents. Ordinary silicone rubber has moderate oil and solvent resistance. (7) Gas permeability. At room temperature, the air permeability of silicone rubber to air, nitrogen, oxygen, carbon dioxide and other gases is 30-50 times higher than that of natural rubber. (8) Physiological inertia. Silicone rubber is non-toxic, tasteless, odorless, non-adhesive to human tissue, has anticoagulant effect, and has very little reactivity to human tissue. Especially suitable as medical material.