Slight Delamination With Duratech

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#1

So I’ve been having a few slight problem with slight delamination with Duratech’s new top coat and VE resin.

My process is spray a mold with about 18 mills of Duratech’s new top coat. Let it cure, then laminate with carbon fiber and infuse with a layup VE resin. I do use a little super 77 but I have never seen this problem with other gel coats like clear marine gel coat.

I catalyze at 2% and let it cure for at least 6 hours before I demold, sometimes I demold after 3 hours if its a two part component where the two halves prevent each other from warping.

Here is an image of the slight delamination. The highlighted spots on the top of the carbon tows are the problematic area, never the low points in between the fibers where there is more resin.

Theories - resin starvation on some of the fibers? I say that because the intersections don’t show signs of delamination. The intersections are where there is more resin mass because for that 1mm x 1mm area there is no fiber.

Another theory is I’m allowing the top coat to cure too long. I understand that its a high solid top coat, meaning non porous. Any thoughts? I usually don’t infuse for 12 - 36 hours.

Last theory is cohesion. I doubt there are cohesion problems because I’m trying to laminate carbon with VE resin over poly resin. However I have had worse issues with a VE / Poly blend infusion resin.

Possible solutions?

Maybe allowing full cure and sanding with a 3" orbital sander to 320. But then I’m relying on a mechanical bond, not chemical, right? Or would I still get some chemical bond since it would be less than 36 hours.

Ideally I want to infuse after 4 hours, but when I get some fish eyes I have to drop in duratech and then sand it later, and I can only sand after 12 hours of curing.

#2

John,

I have never used that product but I do use something similar and have had the same issues. The problem was humidity and temperature. If you are curing with a RT resin try putting the part in an oven at 60°C during the cure. That’s what solved my issues.

#3

I don’t know if that works because the ONLY in mould clear I did I had spots like that. I think parts of my spots were from bridging which was just carelessness but I put my item in a 160f oven for 8 hours after a 12 hour RT cure and it still came out like that.

Before that I let my clear coat dry in the mould for 12 hours. It was finishline 1 from sherwin williams auto paint store.

#4

From my understanding water absorption occurs when the resin is still “wet” so you need to put it in the oven before it begins to cure.

#5

Are you using Duratec Polyester Clear Hi-Gloss Topcoat? It is a top coat and not an In-Mould Coating. Among the listed features is “easy to sand”. I think that is a big clue as to the source of your delamination. It is probably easy to sand because the surface cures rapidly. And one has to ask what chemistry are they using to achieve the rapid cure. If that is the case then your V/E is not bonding to it. The surface of the applied topcoat may have some kind of wax or similar coating on it as well.
I haven’t used that product but I started using Duratec Primer as an In-Mould Coating around 25 years ago. I was advised at the time that it was not designed for that application. But it was very successful and I have built quite a few boats using it. However after a break from the industry, I used the product again. And had delam problems. I called Hawkeye Industries, and all they could tell me was that the product had a new formula. I haven’t used their products since then.
The Super 77 seems to work fine with styrenated resins.

#6

One thing I was told was that, that isn’t delamination. That’s air. Which makes sense because more and more my parts have been coming out filled with air. I believe its due to the resin degassing because its staying liquid longer. Its a liquid for a longer period of time because its been abnormally cold here the past week in south florida. Today it seems like its back to normal do I’ll try itout.

I was also told to lower the vacuum from 27hg to 20hg after the infusion is finished to not separate the styrene from the resin, or vacuum the resin out of the fabric. Any thoughts?

#7

John,

I don’t believe you have a duratec problem. From your image it appears that you have a very sharp edge on the area where the air entrapment has occurred. You can do the following and it may help:

  1. Apply pressure pads on that area (molded Silicon pads)
  2. Use less areal weight carbon as top layer and immediately underneath, where you have the sharp edge, make a resin/flox/milledfiber fillet which will then distribute pressure.
  3. Apply higher vacuum.
  4. Degas resin.

The above singularly or in combination should enable you to address the issues.

N

#8

I also believe that it’s air trapped and a very thin layer of Duratec judging from the print through. Also depending the room temperature the resin gets thicker or thinner. Maybe the temperature was low and the resin was thick and didn’t flow well.