Epoxy gelcoat vs polyster gelcoat

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Epoxy gelcoat vs polyster gelcoat

Author	Message
Hansson43	H Hansson43 posted 5 Years Ago HOT Topic Details
H Group: Forum Members Posts: 23, Visits: 2.1K	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
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Matthieu Libeert	Matthieu Libeert posted 5 Years Ago HOT Post Details
Group: Forum Members Posts: 955, Visits: 3.4K	+x 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 epoxy will bond well to polyester - polyester won't bond well to epoxy... that's the first rule you need to keep in mind while working with composites. BUT when you've properly released your mould with release agent you shouldn't have any problem. Would recommend you a chemical release agent to be sure. I make all my moulds with the Uni-mould systems and do 90% of epoxy parts in them without any problems. Epoxy should in theory be stronger, stiffer for moulds than polyester. Polyester would be subjected to more shrink/warping and less high temp resistant BUT the uni-mould system is a very stable polyester based system that can be polished to high gloss and a thick CSM + toolingresin build-up can be done in 1 go Matthieu Libeert Founder MAT2 Composites X Sports website: www.mat2composites.com
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oekmont	oekmont posted 5 Years Ago HOT Post Details
Group: Forum Members Posts: 550, Visits: 27K	The unimould system uses a vinylester tooling gelcoat. polyester gelcoat often makes problems during demoulding, when using epoxy resins. It can work, but it is not the safest method.
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Matthieu Libeert	Matthieu Libeert posted 5 Years Ago HOT Post Details
Group: Forum Members Posts: 955, Visits: 3.4K	+x oekmont - 1/8/2019 1:58:25 PM The unimould system uses a vinylester tooling gelcoat. polyester gelcoat often makes problems during demoulding, when using epoxy resins. It can work, but it is not the safest method. correct about the gelcoat and coupling coat being vinylesters, the tooling resin is polyester if I'm correct in that Uni-mould system. Matthieu Libeert Founder MAT2 Composites X Sports website: www.mat2composites.com
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Hansson43	H Hansson43 posted 5 Years Ago HOT Post Details
H Group: Forum Members Posts: 23, Visits: 2.1K	Thank you! Now I think I get it. So if I have some glasfiber and epoxy left I can use it to make molds with the uni-mold system ?
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oekmont	oekmont posted 5 Years Ago HOT Post Details
Group: Forum Members Posts: 550, Visits: 27K	Probably. But definitely not recommend. If you got the unimould system anyways, I would stick to the plan and make the whole mould as intended. Why would you substitute cheap polyester with epoxy, which you could use later for the parts you are making?
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oekmont	oekmont posted 5 Years Ago HOT Post Details
Group: Forum Members Posts: 550, Visits: 27K	Epoxy bonds quite good with cured polyester. The polyester/vinyester gelcoats however are designed to not fully cure at the outside, to give a reactive surface with the backing polyester. As epoxy is chemically very different to polyester, it doesn't react with the surface, leaving it partially uncured.
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Hansson43	H Hansson43 posted 5 Years Ago HOT Post Details
H Group: Forum Members Posts: 23, Visits: 2.1K	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 ?
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JasonFL	JasonFL posted 5 Years Ago HOT Post Details
Group: Forum Members Posts: 51, Visits: 707	+x 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. Jason
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