‘What temperatures can silicone rubber withstand?’ is a question the team at Viking Extrusions are commonly asked by designers and engineers looking to assess the material’s suitability for their application.
Interestingly, there isn’t a default answer our silicone experts can offer without asking further questions about the environment in which the silicone will be operating.
Unlike most other types of rubber, silicone can withstand extreme temperatures from as low as -60°C to +200°C while maintaining its properties. Once critical factor which determines the operating temperatures silicone can really withstand is the length of time of exposure, which has a key impact on performance and lifespan.
For most applications where parts are exposed to continuous temperatures over 150°C will require the use of silicone rubber to ensure performance and longer life span.
How hot can silicone get before it melts?
Silicone does not melt due to temperature alone!
Most plastics begin to melt at high temperatures. Silicone, however, exhibits unique behaviour at elevated temperatures. Silicone does not have a melting point but instead remains solid until combustion occurs. At high temperatures (above 200°C) silicone will begin to slowly lose its mechanical properties becoming harder and more brittle. At temperatures above 300°C this process is accelerated. There is no set temperature for silicone auto ignition which can depend on may factors such as the hardness of the silicone, type of curing catalyst used, and any additives or pigments However, auto ignition generally occurs around 450°C.
Silicone’s behaviour during combustion
Silicone also displays unique behaviour during the combustion process. Once autoignition temperature has been reached, the material will briefly smoke before it cracks and begins to combust. At this stage the silicone will expand in volume and volatiles are released, before brittle combusted material breaks away from the sample and disintegrates into a fine powder.
Silicone is made from a silicon-oxygen-silicon backbone with carbon-containing methyl and vinyl groups. During combustion, silicone dioxides and carbon dioxides are produced. The carbon monoxides and carbon dioxides are released into the atmosphere. The silicon dioxide creates a layer of white powder on the sample. This layer of silicone dioxide cannot combust any further, it acts as an insulating layer which helps to slow down or prevent further combustion of the silicone.
What temperatures can different grades of silicone withstand?
General Purpose Silicones
General purpose grades of silicone are suitable for continuous exposure of temperatures up to 180°C and intermittent exposure up to 200°C.
Heat stabilised silicone
Heat stabilised silicones contain additives that increase their maximum operating temperature to 260°C.
High temperature silicone
High temperature grades of silicone contain additive that make them suitable for applications up to 300°C for intermittent periods. If the part is to be exposed to continuous temperatures over 300°C then the silicone’s properties would degrade with time.
Flame retardant silicone grades
Flame retardant grades of can withstand intermittent temperatures up to 220°C (depending on the specific grade). These materials contain additives which enhance silicones self-extinguishing properties. A variety of flame retardant grades are available specifically formulated to meet standards such as:
- CS 25.853
For detailed information on all of the silicone grades we offer, visit our technical datasheets page.