Silicone rubber with excellent heat resistance, cold resistance, dielectric properties, ozone resistance and atmospheric aging properties, outstanding performance of silicone rubber is the use of a wide temperature range can be -60 ℃ (or lower temperature) to +250 ℃ (or higher temperature) long-term use. However, the tensile strength and tear strength of silicone rubber and other mechanical properties are poor, its physical and mechanical properties at room temperature less than most synthetic rubber, and in addition to nitrile silicon, fluorosilicone rubber, the general resistance of silicone oil, solvent resistance Poor, so silicone rubber should not be used for general conditions of the occasion, but very suitable for many specific occasions.
It is worth mentioning that, in biomedical engineering, polymer materials have a very important role, and silicone rubber is a particularly important class of medical polymer materials, it has excellent physiological inertness, non-toxic, tasteless, no Corrosion, anticoagulant, good compatibility with the body, can withstand harsh disinfection conditions. Can be processed into pipes, sheets, films and special-shaped components as needed, which can be used as medical instruments, artificial organs and so on. At home and abroad now have specialized medical-grade silicone rubber.
Among the many synthetic rubbers, silicone rubber is one of the best. It has the characteristics of tasteless, non-toxic, not afraid of high temperature and resist the cold, at 300 degrees Celsius and minus 90 degrees Celsius "calm", "no change of color", still without losing the original strength and flexibility. Silicone rubber also has good electrical insulation, oxygen aging resistance, light aging and mildew resistance, chemical stability. Due to these excellent properties, silicone rubber has played an important role in modern medicine. In recent years, by the hospital, research institutes and factories to work together to successfully trial a variety of silicone rubber medical supplies.
Silicone rubber vulcanization mechanism can be divided into three categories: organic peroxide induced free radical crosslinking type, polycondensation reaction type, addition reaction type.
With the main agents include: reinforcing agent, curing agent and some special additives, generally require 5 to 6 components can be composed of practical formula.
Formula Design Note:
1. Silicone rubber is a high degree of saturation of raw rubber, sulfur vulcanization is not usually used, the use of thermal vulcanization, thermal vulcanization using organic peroxide as curing agent, therefore, the raw rubber can not contain peroxide decomposition products can play an active role Materials (such as channel black, some organic accelerators and antioxidants, etc.), otherwise it will affect the curing.
2. Silicone products are generally used at high temperatures, the compound should be stable at high temperatures, for which inorganic oxides are usually used as a reinforcing agent.
3. Silicone rubber in a trace amount of acid and alkali and other polar chemical reagents easily lead to cracking and rearrangement of siloxane, resulting in reduced heat resistance of silicone rubber. Therefore, the choice of compound must take into account its acid-base, but also should consider the acid and alkali peroxide cracking products, so as not to affect the performance of vulcanized rubber. (Silicone rubber is non-polar rubber).