This is happening intermittently, sometimes days after applying the first coat of duratec sunshield to parts. The duratec was sprayed on, then brushed in to fill some voids. After a few minutes flash time it was placed in an oven at about 140F to cure for a few hours. The following day, it was block sanded and coated again. The guy doing it didn't notice the porosity until I pointed it out, so I can't say for sure when it appeared exactly, but it looks to me like the first layer was still out-gassing while the next coat was applied. Putting it in the oven to cure the second coat probably exacerbated the problem. I suppose our recourse at this point would be to oven cure the first coat 24 hours or so before moving on, and we can be a bit speedier with the later coats. The duratec was not thinned or modified in any way. Any thoughts or experience with what's going on here?

Is that how the voids are appearing, or has it been sanded back and they are collecting sanding dust? If it is the latter, are you sure it isn't just shrinking back into the voids you were filling in the carbon? It sort of appears like typical lean laminate voids, like it is at the junctions between fibres. But then I can also see some that don't really look like that, but figured it was worth mentioning.

I never had any issues like this with Duratec, and I was processing in much the same way. Realistically, I think Duratec flashes off and outgasses much much quicker than a polyurethane, so I've never run into any gassing problems with Duratec. I've had a bit of solvent pop before from going too heavy and smashing the clear coat on with 3 or 4 wet coats, but this isn't solvent pop.

In my experience, Duratec Sunshield is very poor as a final coating, I only use it for pattern coating these days. It wears very poorly, and despite its name it actually provides precisely 0 UV protection. It doesn't even last one year here in our Australian sun.

+x

 

Hanaldo - 9/11/2020 12:04:23 AM

Is that how the voids are appearing, or has it been sanded back and they are collecting sanding dust? If it is the latter, are you sure it isn't just shrinking back into the voids you were filling in the carbon? It sort of appears like typical lean laminate voids, like it is at the junctions between fibres. But then I can also see some that don't really look like that, but figured it was worth mentioning.

I never had any issues like this with Duratec, and I was processing in much the same way. Realistically, I think Duratec flashes off and outgasses much much quicker than a polyurethane, so I've never run into any gassing problems with Duratec. I've had a bit of solvent pop before from going too heavy and smashing the clear coat on with 3 or 4 wet coats, but this isn't solvent pop.

In my experience, Duratec Sunshield is very poor as a final coating, I only use it for pattern coating these days. It wears very poorly, and despite its name it actually provides precisely 0 UV protection. It doesn't even last one year here in our Australian sun.

Thanks Hanaldo. These are voids under the ‘skin’ of the coating, so there’s no real hope of filling them back up again. They appear under the clear during the later stages. This was a particularly bad part; usually we don’t have voids like this to fill. Fortunately this is being sent as a ‘2nd quality’ part because it didn’t pass our QC to begin with.

There are a lot of mixed emotions and experiences with duratec sunshield. Some people say it’s awesome and lasts years and years, others say it doesn’t work. We used to use a prestec product marketed similarly but it was cloudy. The Duratec clears up nicely. We use it as a base for a 2K urethane clear over top. It gives us some material to block sand to get the surface absolutely straight and true, and if it works properly, to fill any pinholes and small voids. Very frustrating that it’s been intermittent. Trying to isolate variables.

That looks like a layup issue with air in the fabric and not the duratec.

Not disputing the presence of voids in the surface of the laminate - we're rescuing it with the duratec. The bubbles are forming in those voids between the first layer of duratec and the laminate, long after we've applied 2nd and 3rd coats of more duratec. 

Or are you saying there's air trapped in the laminate and we're causing it to escape by curing it further in our hot duratec curing process?