Silicone (Q) resins are man-made elastomers that combine high heat resistance with good cold resistance to produce materials that offer many advantages over natural rubber. Elastomers are polymers that are both viscous and elastic. Other elastomers include butyl rubber, fluorocarbons, neoprene, nitrile, polysulfides, and natural rubber. Silicone resins typically produce thermoset products, but there has been success in developing remeltable thermoplastic elastomers or TPEs. Information on other polymers can be found in our resin types guide.
Properties
Silicone resins are manufactured in three main forms: LSR, or liquid silicone rubber; RTV, or room-temperature vulcanized silicone rubber; and HTV, or high-temperature vulcanized silicone rubber. LSR is used to make many heat-resistant parts used in everyday applications, such as spatula blades. RTV silicone rubber is used to make, for example, in-situ cured engine gaskets. LSR is a thermosetting material, which means that once cured, the material cannot be returned to its original shape. It is usually injection molded because the material flows well, although this requires a more complex process than regular thermoplastic injection molding. The material is usually a two-part, low-viscosity compound that can be heat cured. The material has an excellent temperature range, UV resistance and high optical clarity. It is usually sold in bulk containers or drums. Another type of thermoset HTV silicone rubber (sometimes referred to as HCS or high-consistency silicone) is usually sold as a solid, partially vulcanized, gelatinous rubber mass. It is often referred to as "grindable" silicone rubber. The material is usually compressed, sometimes resin-transferred, and molded using standard rubber molding techniques and machinery. HTV silicone rubber is also available in liquid (LSR) form. Silicone tubing and other shapes are typically extruded from HTV silicone rubber. rTV silicone rubber is available as single (RTV-1) and two-part (RTV-2) formulations. In addition to its many applications as a construction sealant, it is often the choice for potting and encapsulating electronics. The material is available in two forms. Condensation-cured RTV contains a tin catalyst and relies on atmospheric moisture to reach its hardened state. Additively cured RTV contains a platinum catalyst and does not require atmospheric moisture to cure.
Applications
Silicone rubber is often the choice for applications where high temperatures make other elastomers unsuitable. It is considered non-toxic, making it safe for use in food contact, implants and more. It has high electrical resistance, withstands steam sterilization and is easily colored. Its mechanical strength and abrasion resistance are poor. Various fillers and chemical additives are compounded into the material to improve its application in specific products. Carbon black can be used to increase electrical conductivity and is used in cable connectors, keyboards, and more. The hardness of the material can be varied, from soft gels used in shoe insoles to medium-hard rubbers that can be used with many thermosets and thermoplastics. Additives can also improve thermal conductivity, flame retardancy and adhesion. The biocompatibility of silicone rubber allows it to be used in many products that come into contact with the body, such as face masks, mouthpieces, urinary catheters, baby pacifiers, and pacifiers. The material is more commonly used in cookware, such as muffin pans, where its heat resistance and inherent smoothness provide a flexible alternative to PTFE-coated baking pans. It does not impart any taste or odor to food. Silicone rubber is also used as a mold-making material because it has low shrinkage and reproduces detail well. Soft molds can be used to mold products with negative draft angles because parts are easy to remove. Silicone is making inroads in 3D printing. Unlike most rubbers that use carbon black in compounding, silicone is naturally transparent, making it suitable for applications where flexibility and visibility are important, such as keyboards and remote control covers. Excellent compression set properties make it the material of choice for many gaskets and O-rings. Its low wear resistance often limits its use in static, non-operating seals. Silicone resins are also used in lubricants, mold release agents, specialty films, and dielectric greases.
Physical Properties
Silicones differ from most elastomers in that they are silica and oxy (with hydrocarbon side groups) rather than carbon and hydrogen groups. The silicon dioxide-oxygen-silicon dioxide atoms form the backbone of the molecule (siloxane) to which the organic molecule is attached. Despite its poor mechanical properties, the material is able to maintain these properties over an operating temperature range of -70°C to 250°C. The material can be used in a wide range of temperatures. Higher temperature grades are available for use at temperatures above this level.
Chemical Resistance
Silicone resins used with mineral oils, such as gaskets or O-rings, can be modified to improve resistance to these fluids, but they are relatively resistant to petroleum and hydrocarbon solvents. Fluorosilicone rubber (FVMQ) has been developed for use in contact with jet and automotive fuels, solvents and engine oils. Silicone resins can handle general chemicals better. The material has excellent UV and ozone resistance as well as high breathability. The material does not support the growth of mold or fungus. Formulations with improved fire resistance are available.


Room termperature curing polysilazane, pls check IOTA 9150, IOTA 9150A. 
High termperature curing polysilazane, pls check IOTA 9108, IOTA 9118.