PVA + Gelcoat in mould, for adhesion to epoxy laminate

Since epoxy is used to bond polyester parts together... Epoxy laminate over gelcoat in mould should be fine.

But it isnt,

Unwaxed gelcoat is used in moulds, so the surface cures very slowly, presenting ready bond for polyester laminate...

Waxed gelcoat in a mould will cure, in hrs... but then there is wax inhibiting laminate bond....

What if PVA is used over the gelcoat... it will fully cure, allowing for good adhesion to epoxy laminate????...with some light sanding to key surface.

 

And...you need to wash the PVA off with water, then sand.

There are epoxy compatible gel coats.

 

Guess I'm testing the premise that chemically gelcoat is coloured, thickened polyester resin....

Cause all polyester laminates are compatible with epoxy.... if surface preped correctly...

Then all gelcoats are also compatible with epoxy....

In a commerical setting, no one is going to PVA-sand or use peelply...Hence the "compatibility" problems.

But for smaller parts PVA is an option. Tks

 

What I'm saying is that while yes it could be done, there are much easier ways to get a gel coat finish on an epoxy part.

Duratec products are designed for this type of application, they cure tack free for in-mold use with epoxy (they work with Polyester and VE too).

 

I was told epoxy only bonds well to old polyester products as in no strine smell.

 

In a mold, would an epoxy lamimate bond better to poly gelcoat that has had the Duratec high gloss additive mixed in?

 

You need to add enough for the surface to cure tack free, or just use a high ratio of clear additive in the final pass.

 

Hi Ondarvr,
I am looking to infuse epoxy over gelcoat for my hull. What Duratec product would you recommend. I can get Duratec products but can’t find a epoxy compatible gelcoat that is UV stable and can be submerged in water for long periods. I was looking at Duratec Sunshield but this is expensive. It sounds like you are talking about a Duratec product that can be added to polyester gelcoat to make it compatible with epoxy? Is this the product below?
Thanks

 

What size boat and will it be kept on a trailer or in the water for extended periods of time?

 

24.5 foot boat. It will be a production boat. So some will live on trailers and others will live on a mooring so will be in water for extended periods.
Thanks

 

Constant immersion is the toughest situation, it tests the bond more than anything else.

You need to test it with the exact epoxy you plan to use, not all epoxies are created equal.