Really weird problem with tooling gelcoat and semi perm

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#1

I searched the forum and couldn’t find this exact issue- apologies if it’s been discussed previously…

Poly and fiberglass mold with tooling gelcoat, wet sanded, polished, and buffed to a mirror finish, clean mold, seal mold, and finally treated with a semi perm. (not that it should matter, but this tool in the pic is for a vehicle hood)

After infusion, I’m getting a haziness in spots (on the tool and transferring into the part) that looks like slight alligatoring, (but more like a rough patch of graininess). You cannot physically feel any kind of roughness in the tool’s surface, just a haze where the mold is no longer glossy. This only happens when using polyester resin and a polyester gelcoat as an IMC. (weather I infuse or spray with chopper gun) The part still releases effortlessly- it’s just the mold get’s a larger, grainy, hazy section somewhere on the tool’s gelcoat after each part that is removed from the tool. I can’t keep polishing and reapplying release between parts. It’s just not productive.

If I use Duratec clear topcoat or sunshield as an IMC, laying up carbon specifically, and infuse with epoxy- the tool is perfect.

I don’t want to name the company for the semi perm as of yet because they have been super helpful and have asked me to try EVERYTHING… and I have done everything I know to do. They have gone so far as to send me samples of everything they offer. It still happens no matter what. Also, the few distributors that I deal with are clueless as well.

The picture is hard to see, but yes- that grainy texture is what is happening somehow and again, you physically can’t feel it.

Obviously, it’s something with polyester on the tooling gelcoat having a reaction, but why?

A friend of mine uses the exact same processes as me with the exact same release and he doesn’t have this issue when making poly parts.

Suggestions?

#2

probably not fully cured, styrene still coming out there. Usually on the first part or two off a new PE/VE mould it is suggested to use PVA to avoid this from happening. You can also try post curing it at a high temp for a couple hours then repolish it. Should not come back.

#3

Yup. “Seasoning” all of my tools with PVA on the first few runs. Molds are perfect until semi perm is used with poly. I haven’t tried post curing though. How high of a temperature should I be using?

#4

Ive seen the same thing happen as you shown on PE/VE moulds. Usually its in small areas, and very few. Not sure about the frequency of your problem, and Im not sure if the problem occurs because the gelcoat is too thick, or too thin in these areas. I could come up with reasons why for both cases. At any rate, depending on your tooling system, try 50C for 2-3 hours.

#5

I post cure all my molds at a slightly higher temp than when in production for several hours. Havent had this issue. I use the orange tooling gel from US Composites, which is kinda cheap (money wise) and don’t have issues.

#6

Making another mold. Same process as before, and I will use the chopper gun to build thickness. I have a small, makeshift oven that will max out at 150F. At what point should I put the mold in the oven? After room temperature full cure?

Thanks guys in advance. Been doing this a while now and have never had this problem- even with the same semi perm. I’m just baffled, and so is everybody else I have spoken with. :frowning:

#7

It looks like flakes of dry pva stuck in the gel coat.

It’s weird that you wouldn’t be able to wash that off though.

How many layers of wax and pva did you use and how long did you let each one dry before using the mold?

Is it possible that you are using too much resin and the excess is fish-eyeing on the back of the gel coat layer?

How is is laid up in the mold? I.e. Do you apply the gel coat, let it semi cure, then wet lay the cf or fiberglass? Is your pva sprayed or brushed on?

#8

Do you wax over the semi perm release? Can’t see what the cause is from your photo, but that may stop it from happening.

#9

Are you suggesting adding mold release wax on top of the PVA?

#10

He isn’t having the problem occur when using PVA, only once he switches to a semi-perm and then lays up a polyester part.

Very strange problem, I’m totally stumped. I would suspect it has much more to do with the tooling gelcoat rather than the release agent, and under-cured would be my guess. But it is a strange one for sure.

#11

No. Although that can be done. Wax over the Semi-perm release.

#12

I’m completely stumped as well. Changed tooling gel coat and am currently using an “in house” brand from my local supplier. They sell to a ton of the boat guys in my area. No one has reported this issue to them and I’ve never had this problem until recently.

I baked this new tool up to 150 degrees Fahrenheit for 4 hours. Same issue.

I guess it’s time to try a different semi perm.

Thanks everybody for the responses.

#13

Let us know if an alternative semi-perm changes the issue. I can’t possibly see how it would, so it’s very interesting if it did.

#14

I will. Thanks again.