A Complete Guide to Silicone Rubber

Silicone rubber is a popular high-temperature synthetic elastomer used for various applications within most industry sectors. Due to its excellent temperature resistance, FDA approval and non-toxicity properties, Silicone is the preferred rubber compound for manufacturing products for the medical and food industry. However, with superb general resistance to most substances, Silicone rubber seals can be used within almost every industry sector for most applications. With a heavy reliance on synthetic rubber compounds, Silicone has taken its place as one of the most common and widely used raw materials for manufacturing seals and associated products. Silicone can be extruded in a range of hardnesses and densities in solid or closed-cell materials.

This article provides a background to the history of Silicone, how the compound is created, and discusses the benefits of using it to manufacture bespoke extrusions and cut rubber strip.

Silicone is a versatile general purpose material that can be used for a diverse range of applications that cannot be achieved with other rubber compounds. With a unique set of properties, Silicone is often the preferred material for projects requiring a high-temperature and long lasting sealing solution. Some of the key characteristics and properties of Silicone rubber include;

• Temperature Resistance: Operating within a temperature range between -60°C and 230°C, seals manufactured from Silicone rubber can withstand extremely low and high temperatures. Remaining flexible below freezing, Silicone is well-suited for applications in cold climates and cryogenic environments. It can also withstand elevated temperatures up to approximately 230°C without significant degradation of its physical properties. This makes it suitable for use in exceptionally high-temperature environments, such as automotive engine components, ovens and industrial applications.
  
  
• Weathering: Similar to most other synthetic rubber compounds, Silicone can withstand exposure to the elements making it suitable for seals manufactured for outdoor environments. It exhibits good resistance to UV and ozone, which helps maintain its physical properties and colour when used outdoors for extended periods of time. Rubber seals manufactured from Silicone also demonstrate outstanding water resistance and are impermeable to moisture.
  
  
• Chemical Resistance: Silicone rubber is resistant to a wide range of chemicals, including acids, solvents and other common industrial chemicals. The material can withstand exposure and contact with many corrosive substances without significant degradation.
  
  
• Food Safe: Silicone extrusions can be manufactured from metal detectable and FDA approved materials that are considered safe for contact with food. As food safe Silicone is biocompatible and non-toxic, it can also be used in medical devices, implants and prosthetics.

In addition to being a material suitable for use in food factories and extreme temperature environments, Silicone exhibits other properties that make it an ideal material for most sealing applications. These properties include;

• Flexibility and Elasticity: Silicone is a highly flexible and elastic rubber compound that can stretch or compress and return to its original shape without permanent deformation. This is a useful characteristic for sealing applications where the section will be compressed to create a reliable watertight seal.
  
  
• Low Production Runs: Although Silicone extrusions are more expensive to produce than those manufactured in other synthetic compounds, the minimum production run is often significantly lower. This helps reduce the overall price for the extrusion in situations where you only require a small quantity. As Silicone rubber is known for its durability and resistance to aging, seals manufactured in this material also need to be less frequently replaced so offers an ongoing cost saving.
  
  
• Closed-Cell: Gases can be injected into the rubber compound during the extrusion process to make a compressible sponge. This is a closed-cell material that does not absorb water and can be used to create watertight seals on hatches, doors and lockers. In the same way as other closed-cell products, Silicone sponge seals can be extruded into almost any shape in any size with fine details.
  
  
• Colours Matching: It is possible to manufacture custom Silicone sections to any colour specification. The compound is pigmented during the manufacturing process to match the colour of an existing seal or RAL colour number. This is particularly useful for instances where you need an extrusion that matches your companies branding, or are required to use a colour that can be easily identified in food and drink manufacturing environments.
  
  
• Metal Detectable: As Silicone is commonly used within food processing and manufacturing environments, it is possible to extrude Silicone rubber seals in metal detectable grades. This type of rubber contains metal particles or additives that allow machines using metal detectors to identify failed seals and trims that breakdown and enter the food supply.  This is essential for industries where contamination control is crucial.

Although Silicone rubber has many advantages, such as its high-temperature resistance and flexibility, it also has some disadvantages that make it unsuitable for specific applications. Some of these disadvantages include;

• Fuel and Oil Resistance: Silicone rubber exhibits moderate resistance to occasional or short-term exposure to fuels and oils under certain conditions and temperatures. However, constant contact with these substances under the wrong circumstances will cause the rubber to swell and deteriorate. For applications that require a rubber compound suitable for contact with fuels and oil, we recommend using Nitrile or Viton which offer an excellent resistance to these substances.
  
  
• Poor Adhesion: As Silicone rubber has a naturally non-stick surface, it can be difficult to bond to other materials. Silicone sealants or special primers are the only adhesives that can achieve adequate adhesion and bond  Silicone based products to other substrates. This can limit the use of Silicone extrusions to applications that do not require very strong adhesion.
  
  
• Poor Tear and Abrasion Resistance: Seals manufactured from Silicone have a relatively low tear strength compared to other elastomers, such as EPDM and Neoprene. This makes the material less suitable for applications where the seal will be fitted in environments that could cause it to tear or puncture. Silicone also offers poor abrasion resistance.

Silicone rubber is available in a selection of types and grades that can be used in most industry sectors. Each variant offers different properties, characteristics and benefits that make it possible to select the correct Silicone compound most suitable to the required application. Our range includes materials suitable for contact with food in food factories, high temperature environments or low-quantity prototyping. Silicone can be cut from sheet or extruded in sponge and solid compounds to create trims suitable for edge protection or sections that can be used to create a watertight seal.