Extrusion is a process where the material goes through plastic deformation through the application of force, causing the material to flow through an orifice or die. The extrusion process helps to create an excellent finish to the material and also gives freedom of form in the eventual design process.
There are actually two different types of extrusions that are used for fire safety. Heat-resistant silicone extrusions and flame-retardant silicone extrusions are often confused with each other, however, they both have completely different properties.
Heat-resistant silicone is manufactured to function properly and maintain its mechanical properties when met with extreme temperatures, both hot and cold. The material can withstand heat up to 305°C all the way down to -70°C, which is a far greater range than any other polymerised rubber material. A good example of a heat-resistant silicone extrusion would be a silicone seal used on an oven.
As you would expect from the name, flame retardant silicone extrusions are also commonly used in fire safety. Flame retardant silicone is so effective as it has been specifically formulated to have the ability to be self-extinguishing. This silicone rubber also has properties of low smoke and low toxicity.
However, flame retardant silicones do not have the ability to withstand such impressive heat ranges as heat-resistant silicone extrusions. These can only withstand temperatures of up to 200°C, although this is still high when compared with other rubber materials.
There are multiple silicone grades that meet flame retardancy requirements for different industries. These include:
- VFR(2) – This is a flame retardant grade of silicone developed for rail applications. It is available in 68 Shore A
- VFR 203-803 – This flame-retardant grade of material is specified for use in aerospace applications and is available from 20 Shore A to 80 Shore A
- EN45545-2 – This particular grade is standard in the railway industry and across other mass transit vehicles.
As silicone is an extremely safe material, it is extremely effective in extruded form to bridge components in moving parts and machinery that could potentially be susceptible to fire hazards.
