I got some end-of-run prepreg.
I tried to make some heelguards.
Issue1: My silicone mold is almost dead!!! Doesn’t silicone last more than 60min at 255deg? WTF?
Issue2: Are there vacbags and seals that work above 255deg? gezz…the bag almost died too!
Issue3: Will fiberglass and resin molds work at high temps? I don’t want to trust silicone again…despite how perfect it is.
air-tech makes autoclave heat and pressure bags that you can get from Evan I believe and there is also gel coats and resins that are for high heat as well. There is a epoxy made for high heat molds you might want to look into as well. I will figure the name of it for you
but I live in an apartment, so something like an autoclave will be too expensive and large!!
hmm…i looked at the temps of the stuff…I think I just got the low temp sealant due to cost. Ha.
I think I just need to make a damn mold and test it. of course, this stuff is also taking up my freezer!!! Luckily it isn’t squashable 
I have the PTM&W HT-1930 black tooling gel coat and the HT-2050 resin. They’re both good for temp up to 331F with proper post cure. The vacuum bag should be good up to 400F and the hi-temp sealant tape is good up to the same range. I’m doing a small run of prepreg helmets @256F for 60mins and everything works just fine.
Also, make sure that it is silicon and not urethane because there’s a big difference. Silicon can withstand hi-heat but at different tolerances. Even then it slowly breaks down after each heat cycle. I’m guessing that the silicon you’re using isn’t made to stand up to high heat for that long.
It is Polytek Tin-Sil silicone…that is for sure. It was a 2 part mold, so that might be the issue…I’m testing another piece right now, that I know is a single piece mold!!
Cool, I’ll get off my ass and get some fiberglass for a rest run soon and if it doesn’t work, I know where to turn!!