Pressure exerted by enclosed volume of silicone

[mr650061]

Can anyone offer insight on how to calculate the pressure exerted by a closed volume of silicone rubber over rise in temperature. The rubber fills the volume completely.

Many Thanks.

 

[Compositepro]

There was a thread on this in the composite engineering forum not long ago. You can do a theoretical calculation but that will only give you an idea of how much pressure is possible, and will not be very accurate in real life.

 

[mr650061]

Can you point me to the thread that you mentioned. If you happen to know the formula to calculate the theoretical pressure that would be much appreciated.

 

[3DDave]

The conclusion of the thread is there is no formula.

 

[Compositepro]

It is the same formula that would be used to calculate water pressure due to heating expansion in a closed pipe. You need the CTE of the liquid and the metal containment, the bulk modulus of the liquid, and the modulus of the metal container. With piping this calculation is done frequently. The issue with silicone is that it is used to apply pressure for making composite parts, so there is always some significant compaction occurring. This behaves as a random void or air bubble in a water pipe, which completely overwhelms all the other factors in the equation. You may as well use a tiny piston pump to apply pressure so you can control it precisely. Pressure gauges rely on the expansion of a Bourdon tube. This change in volume will affect the ultimate pressure.