Silicone rubber is an elastomer (rubber-like material) composed of silicone polymer containing silicon together with carbon, hydrogen, and oxygen. Silicone rubbers are widely used in industry, and there are multiple formulations. Silicone rubbers are often one- or two-part polymers, and may contain fillers to improve properties or reduce cost. Silicone rubber is generally non-reactive, stable, and resistant to extreme environments and temperatures from -55 °C to +300 °C while still maintaining its useful properties. Due to these properties and its ease of manufacturing and shaping, silicone rubber can be found in a wide variety of products, including: automotive applications; cooking, baking, and food storage products; apparel such as undergarments, sportswear, and footwear; electronics; medical devices and implants; and in home repair and hardware with products such as silicone sealants.
Silicone rubber offers good resistance to extreme temperatures, being able to operate normally from −55 to 300°C . Some properties such as elongation, creep, cyclic flexing, tear strength, compression set, dielectric strength(at high voltage), thermal conductivity, fire resistance and in some cases tensile strength can be at extreme temperatures far superior to organic rubbers in general, although a few of these properties are still lower than for some specialty materials. Silicone rubber is a material of choice in industry when retention of initial shape and mechanical strength are desired under heavy thermal stress or sub-zero temperatures.[ Organic rubber has a carbon-carbon backbone which can leave it susceptible to ozone, UV, heat and other ageing factors that silicone rubber can withstand well. This makes silicone rubber one of the elastomers of choice in many extreme environments.
Silicone rubber is highly inert and does not react with most chemicals. Due to its inertness, it is used in many medical applications including medical implants.
Categories based on Cure Chemistries:
Whereas hydrolyzing the appropriate silanes yields "finished" silicone fluids and silicone resins, the components of a silicone rubber still have to be cross-linked with each other (vulcanized or cured). There are three different types of cross-linking reactions:
Aside from the necessary reagents and reaction conditions, addition curing and condensation curing also require a suitable catalyst. A platinum catalyst is needed for addition, and a tin catalyst for condensation curing systems. In contrast, peroxide-initiated curing does not require a catalyst.
Categories based on Cure Temperature:
Based on the Curing temperature silicone rubbers can be divided in to:
Silicone rubbers are usually strengthened by fillers such as silica; other fillers are mixed in to add bulk and colour. Valued for their electrical-insulating properties, chemical stability, and the wide temperature range over which they retain resiliency, silicone rubbers are used in making o-rings, gaskets, automotive parts, tubing, insulators etc.
Categories based on Number of Components
Silicone rubbers can be divided in to two categories based on the number of components needed for cure.
One-part Silicone materials contain all the ingredients needed to produce a cured material. They use external factors – such as moisture in the air, heat, or the presence of ultraviolet light – to initiate, speed-up , or complete the curing process.
Two-part systems segregate the reactive ingredients to prevent premature initiation of the cure process. They often use the addition of heat to facilitate or speed cure.