Properties and Uses of Silicone Rubber
Silicone rubber can be divided into heat vulcanization type (high temperature vulcanization silicone HTV) and room temperature vulcanization type (RTV). The room temperature vulcanization type is divided into polycondensation reaction type and addition reaction type. High-temperature silicone rubber is used to manufacture various silicone rubber products, while room-temperature silicone rubber is mainly used as adhesives, potting materials or molds. The thermal vulcanization type has the largest amount, and the thermal vulcanization type is divided into methyl silicone rubber and methyl vinyl silicone rubber. Methyl vinyl phenyl silicone rubber (low temperature resistance, radiation resistance), other nitrile silicone rubber, fluorosilicone rubber, etc.
1. Properties of silicone rubber products
Silicone rubber has excellent heat resistance, cold resistance, dielectric properties, ozone resistance and atmospheric aging resistance. The outstanding performance of silicone rubber is that it can be used in a wide temperature range, which can be used at -60°C (or lower temperature) to +250°C. °C (or higher temperature) for long-term use. However, the mechanical properties of silicone rubber products such as tensile strength and tear resistance are poor, and their physical and mechanical properties are not as good as most synthetic rubbers at room temperature, and except for nitrile silicone and fluorosilicone rubber, general silicone rubber is resistant to oil and solvents The performance is not good, so silicone rubber is not suitable for ordinary conditions, but it is very suitable for many specific occasions.
2. The use of silicone rubber products
In biomedical engineering, polymer materials play a very important role, and silicone rubber is a particularly important class of medical polymer materials. It has excellent physiological inertia, non-toxic, tasteless, non-corrosive, anti-coagulation, It has good compatibility with the body and can withstand harsh disinfection conditions. According to needs, it can be processed into pipes, sheets, films and special-shaped components, which can be used as medical equipment, artificial organs, etc. Nowadays, there are special medical grade silicone rubber in the world. Silicone rubber has excellent performance in the following fields: high and low temperature stability, inertness (odorless and odorless), transparent, easy to color; wide range of hardness, 10-80 Shore hardness, chemical resistance, good sealing performance, compression resistance Deformation; In addition to the above-mentioned excellent properties, compared with conventional organic elastomers, silicone rubber is also particularly easy to process and manufacture. Silicone rubber products flow easily, so they can be molded, calendered, and extruded with low energy consumption.
3. Points for attention in formula design of silicone rubber products
Silicone rubber is a kind of raw rubber with high saturation. Usually, sulfur vulcanization is not used, but thermal vulcanization is used. Thermal vulcanization uses organic peroxide as a vulcanizing agent. Therefore, the raw rubber must not contain active substances that can interact with peroxide decomposition products. Otherwise it will affect vulcanization.
Silicone rubber products are generally used at high temperatures, and their compounding agents should remain stable at high temperatures. For this reason, inorganic oxides are usually used as reinforcing agents. Under the action of a small amount of polar chemical reagents such as acids and bases, silicone rubber is prone to cracking and rearrangement of siloxane, resulting in a decrease in the heat resistance of silicone rubber. Therefore, when choosing a compounding agent, its acidity and alkalinity must be considered. At the same time, the acidity and alkalinity of the peroxide cracking product should also be considered, so as not to affect the performance of the vulcanizate.
