Talk Composites - The Forum for Advanced Composites

Epoxy gelcoat vs polyster gelcoat

http://www.talkcomposites.com/Topic31555.aspx

By Hansson43 - 1/8/2019 11:45:43 AM

Hi, I wonder what’s the difference between epoxy gelcoat and polyester gelcoat ?
I have been working with epoxy gelcoat and epoxy resin for molds but find it rather expensive.
Is it possible to use polyster gelcoat with epoxy resin or do I have to use polyster resin with polyster gelcoat?

Best regards
By JasonFL - 4/17/2019 2:00:58 PM

 
Hansson43 - 1/9/2019 2:45:52 PM
Thanks good point I haven’t thought about that. I just bought what the guy I’m buying it from said would work.

Polyester does it shrink a lot ?


Yes polyester has potential to shrink a lot.  If you layup parts of your mould too thick they can get super hot (exothermic reaction) and cause voids as well as your gelcoat to pull away from the plug.  In general, epoxy moulds will retain the dimensions of your plug much better than polyester will.

A really cheap way to make epoxy moulds is to mix plaster, chopped glass, and epoxy to a clay like consistency.  Use this to build thickness after you have a few layers of cured woven cloth down.