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Write synthesis, properties and applications of silicon rubber.
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Silicone rubber is an elastomer (rubber-like material) composed of silicone, which itself is a 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.

 

Synthesis of Silicone rubber

The most common method for preparing silicone rubber involves reacting a chlorosilane with water. This produces a hydroxyl intermediate, which condenses to form a polymer-type structure. The basic reaction sequence is represented as:

This is the favoured route although other raw materials such as alkoxysilanes can be used. Chlorosilanes and other silicone precursors are synthesised using the “Direct Process”, involving the reaction of elemental silicone with an alkyl halide thus,

Si+RX⟶RnSiX4-n  (where n=0 to 4)

Preparation of silicone elastomers requires the formation of high molecular weight (generally greater than 500000g/mol). To produce these types of materials requires di-functional precursors, which form linear polymer structures. Mono and tri-functional precursors form terminal structures and branched structures respectively.

 

Properties of Silicone rubber

Silicone rubber offers good resistance to extreme temperatures being able to operate normally from -100 °C 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-to-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.

Applications of Silicone rubber

  • Industrial Machinery & Equipments
  • Food & Beverages processing
  • Medical Equipments
  • Chemical & Adhesive filling systems
  • Transformer & other electrical equipments
  • Insulator in electronic & Electric equipments
  • Lighting Equipments.
  • Pouch Packing Machine.
  • Thermal Insulation.
  • Hospital & Medical
  • Pharmaceutical
  • Pharma Machines
  • Textiles & Garment Finishing equipment
  • Packaging Industries
  • Dairy & Automobile Engineering
  • Plastic Machine
  • Healthcare Industries
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