Talk Composites - The Forum for Advanced Composites

Priming and finish coat for plug?

http://www.talkcomposites.com/Topic14248.aspx

By WHY69 - 12/21/2014 11:54:27 PM

I'm making a plug with polyurethane casting resin via silicone mould. I'm planning to then use this plug to make a mould from using the unimold system or similar product (for out of autoclave pre preg CF). I have plenty of questions but mainly I'm wondering if I should prime and gel coat the polyurethane casting resin (plug) prior to making the mould?  If so what products are compatible for what my plans are. 

Polyurethane casting resin plug>
Vinylester tooling coat etc mold (unimold)>
Prepreg carbon fiber out of autoclave finished product. 

I've read and read everything I can but I'm still unsure of what products will interact badly with others and I want to make sure if I need a primer and gloss coat for the mold I use something that will work. Obviously there will be a release agent between the plug and mold made from it but I don't want to use the wrong product that may react badly with the polyurethane casting resin. 

Thank you for any insight you folks might have. 
By matthieutje65 - 12/22/2014 10:17:58 PM

I can not tell you I'm 100% sure, because I havent tested it yet but you dont have to gloss your PU you've casted... 
just sand it smooth till 2000 grid or more and polish If you want a nice mouldfinish. Add some layers of release, and use tooling gelcoat and unimould.
That way you should get a nice mould for prepreg...

Tip:
Mix a small batch of your casting resin, and try the release and unimould on it.

Keep in mind:
you will have to postcure your PU before making a mould, because you will have to postcure your mould with your part in it (you don't have to, but its better, it will prevent your mould to change shape will postcuring before prepreg)