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Boozehawk
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Im not wanting a gloss finish so the part would be getting a rub. down after demolding anyway. I have some easy composites gelcoat https://www.easycomposites.co.uk/epoxy-bonding-polyester-gelcoat-clear but im not sure i could use this in a mold as a gelcoat. Im just using some cheap fibreglass resin i got at Halfords at the moment as im just practising laying up fibreglass and CF. Im starting to realise im going to have to invest a bit of cash in getting some proper resins and learn more about gelcoating etc.
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Hanaldo
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What materials have you used to make your mould? Is it a polyester gelcoat with polyester laminating resin, or is it a tooling system like Unimould with a vinyl ester gelcoat and a tooling resin reinforcement? If it's a regular polyester tool, I would post cure it very slowly up to 50 degrees. Don't just put it in an oven at 50 degrees, rather do something like 30 degrees for 2 hours, 35 degrees for two hours, 40 degrees for 3 hours, and then go 50 degrees for 16 hours. The slower you can ramp it up to 50, the less likely it is to distort and/or lose gloss. Once cured at 50 for 16 hours, you should be able to make your part in it and do a 16 hour cure at 50 degrees for an initial cure, then allow it to cool to room temperature before removing it from the mould and do another very slow post-cure up to 100 degrees. You'll want to test that the epoxy resin doesn't stick to the polyester gelcoat, I've never had any issues with that when using a semi-perm release agent bit that may just be the specific materials I'm using. Otherwise if it's a RTS like Unimould, you should be able to take the mould to 80 degrees quite safely. Slow ramps and long dwells are the key.
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Rich (Staff)
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Potentially but you would be likely to find that the surface of the resin would deform slightly as the post-cure imparts energy into the part and any uncured resin (on a molecular scale) will move around and chain link with their respective hardener molecules. This often causes the resin to sag on the surface when done out of the respective mould tool and so at the end, you could find that you need to polish the part to bring it back to a smooth, flat finish.
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Boozehawk
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Richie (15/08/2016)
Hi Boozehawk, The High Temp Epoxy has a recommend cure cycle of 24hours at ambient temperature followed by a stepped post-cure cycle as follows to achieve the high temperature properties: 1 hr @ 40'C, 1 hr @ 60'C, 1 hr @ 80'C, 1 hr @ 100'C, 1hr @1 hr @ 120'C and then 2 hours at 140 and 160'c respectively . As such, you'll need a mould tool capable of taking extended periods of time at these higher temperatures. Could the stepped curing process be done with the part removed from the mould after the 40c step as i imagine the fibreglass shld be able to cope with 40c?
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Rich (Staff)
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Hi Boozehawk, Loading into an oven at 100'C is definitely not recommended - Firstly, before looking at curing, Epoxy into a Polyester/Fibreglass mould tool is never recommendable as epoxy generally bonds to the tooling gelcoat regardless of the release agent. The next issue is that a normal fibreglass tool wouldn't stand up to those sorts of temperatures. The High Temp Epoxy has a recommend cure cycle of 24hours at ambient temperature followed by a stepped post-cure cycle as follows to achieve the high temperature properties: 1 hr @ 40'C, 1 hr @ 60'C, 1 hr @ 80'C, 1 hr @ 100'C, 1hr @1 hr @ 120'C and then 2 hours at 140 and 160'c respectively . As such, you'll need a mould tool capable of taking extended periods of time at these higher temperatures.
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Boozehawk
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Im making an exhaust end cap for my motorcycle. It is just a surround really so not actually carrying hot exhaust. Ive bought some of the high temp resin an im going to lay up the CF into a fibreglass mold ive made. Would putting it straight into an oven at 100c as soon as ive laid it up be ok with the FG mold? and how long in the oven would be long enough for a good cure?
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ArturK
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Please remember that you need: A) Resin with high TG (as linked) B) Curing at high temperature (>100 C) in order to have a composite that will have temperature resistance more than 100 C .
Carbon fiber sheets and composites . www.dexcraft.com
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dcfoster
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Thanks for the info Meir 
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meir
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There is a high temp resin available
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dcfoster
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Ive been looking into making a valve cover or skinning a valve cover as well making an exhaust tip. Can this be done with Carbon fiber? Im assuming the Fiber itself can handle the heat but im worried about the epoxy. Are there any that can handle high engine temps? or exhaust temps (muffler tip temps)
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