What is the Coefficient of thermal expansion or CTE for silicone at different temperatures?

Question:  What is the Coefficient of thermal expansion or CTE for silicone at different temperatures compared with other steel or aluminum for a 10 inches long example part?

Answer: Thermal expansion is a change in volume or size of something in response to a change in temperature. The molecular interactions in most materials increase with the increase of temperature causing expansion in the material. Thermal expansion is a direct function of the material and silicones expand significantly greater than other materials like metals for the same change in temperature.

Thermal expansion is usually expressed in one of two ways either volumetric expansion or more commonly linear expansion expressed as a coefficient. For example silicone may expand linearly 5.9E-4 to 7.9E-4 in/in-C compared to aluminum at 23.0E-6 in/in-C or steel at 10.8E-6 in/in-C. So for the sake of comparison, a temperature change from 65 degrees to 150 degrees Fahrenheit for a 10 inches long piece would translate to an expansion for a given material of approximately:

Silicone: 0.279” – 0.374”

Aluminum: 0.010”

Steel: 0.005”

The silicone can expand 34X the aluminum and 73X the steel which for higher temperature applications may be worth noting. Many silicone manufacturers do not include thermal expansion rates on their data sheets but will usually provide them by request.

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About Matt

Matt is a project engineer at Albright Technologies, Inc. After interning for two years and earning a Bachelors of Science in Mechanical Engineering from Western New England College Class of 2009, Matt joined Albright Technologies full time.

  • With that amount of expansion it seems it would be possible to use it for something. Automotive thermostats use this principle, when paraffin wax melts (phase change) it expands rapidly and pushes a small piston to open the coolant valve.

  • Mbont

    Hello Michael- There could be silicone applications such as heat driven actuators or switches that when subjected to thermal loading perform some function. Some limitations may be the rate of response and the output repeatability is unknown. The rate of expansion will correlate to the thermal conductivity, so for many silicones the thermal conductivity (0.22W/mK) is about 12% less than that of paraffin wax (0.25W/mK) but the thermal conductivity of silicone can be easily increased with additives like iron oxide. Additionally many sources have reported positive fatigue life for silicone and good thermal resistance so thermal fatigue life may be good but data is sparse. Let me know your thoughts!