Making Molds with Epoxy Gelcoat vs. Polyester Gelcoat

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#1

Hey everyone. I have only used epoxy gelcoat to make my molds for car and bike parts. I then cover the back of the mold with fiberglass, so they are pretty strong. I am thinking about switching to a different gelcoat for making molds. I can get a polyester gelcoat for a little more that half the cost of epoxy. Is it worth it save some money, or should I stick with Epoxy only for my molds? Also, does polyester gelcoat have a strong chemical smell when being mixed? I really like how the epoxy I use doesn’t smell.

If I should stick with epoxy, what gel coats for mold making is everyone using and what kind of prices should I expect.

Thanks for the help.

#2

This is my opinion:

I only build my tooling from epoxy. Its higher strength, toughness, and less brittleness promote a higher tool life. It’s low shrinkage promotes tool stability. I have only built 1 mold out polyester resin. It was a two piece mold and it no longer keyed properly after only two weeks of use. I have epoxy two piece molds that have produced over 100 parts and they still index perfectly.

Some of the newer “zero” shrinkage VE tooling systems sound compelling but I have yet to try them and see if their claims are real.

I also shy away from PE and VE because of the oder and the presence of styrene (known carcinogen). A polyester gel-coat does smell and contain styrene.

I use Adtech ES-221 Epoxy surface coat and self made concoctions out of laminating epoxy.

#3

Thanks! That is what I was thinking, but I figured I would ask and see what others are doing. I really hate when I have to use PE or VE resin because of the oder. I will stick with Epoxy. Ill check out the Adtech ES-221. I use Adtech 820 for infusion and its works great.

Thanks!

#4

Ditto with what wyo said, we are strict epoxy only, I have messed around with polyester gel coats even with epoxy backed moulds and still prefer the epoxy surface coat way better.

The tool lasts way longer, repeatable and predictable results one pull to another. I use PTM&W 1154 for standard moulds, PTM&W 1158 for higher detail moulds and PTM&W 1414 for long run moulds (150+) pulls required.

For high temp I use PTM&W 1520 and when doing pre-preg only the surface coat we use is PTM&W 1945

^^ All good stuff by the way, a little pricey, but real good.