Post-cure process for silicone rubber gaskets 1

[CBRNEngineer]

In order to minimize outgassing of siloxanes, a compression gasket used in military chemical protection filters must be cured in a vented oven at [red]400-500 [°]F[/red] for [purple]four[/purple] hours. At least that's the current requirement but we still have outgassing issues. So, I am considering increasing the time and temperature of the post-curing process. I read somewhere that [red]450 [°]F[/red] is considered an effective upper bound to limit thermal stress on a conventional rubber (see top of page 5 of linked document). Does anyone have hard data to back that up? My thought was to change the requirement to [red]450-500 [°]F[/red] for at least [purple]eight[/purple] hours. Any suggestions would be appreciated.

Tom Green
US Army Civilian

 

[SiliconeAurora]

"Effective upper bound to limit thermal stress on a conventional rubber" is an odd thing for that document to say, given that silicones rarely behave conventionally compared to most other rubbers. In particular, silicone is known for its exceptional temperature range. 600F / 315C is generally the rule-of-thumb upper limit for silicones (Vanderbilt Rubber Handbook, 13th edition.) Your milage may vary, of course, depending on compounding.

Try out your postcure settings and test parts afterward to make sure there is no noticable property drop. I suspect things should be fine.

 

[CBRNEngineer]

Thanks for the response!

 

[GrahamBennett]

We post cure peroxide cured silicone parts for 24hrs at 220 deg C (428 F).