Duratec uv top coat assistance

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#21

I have lots of lubes for sure, keep WD in pump bottles hanging around the lathe and mill to keep the surfaces from rusting but haven’t used them in a while. Much of the composites are done in a separate room but this time of year they can migrate to the warmest area.

I understand the thoughts about contaminates, I really do. I am pretty good about wax and grease removers and letting that evaporate for a while after wiping it off. Always finish with a long blow from the air hose to draw ony out that might not have evaporated. All that said, when I sprayed the 2K clear it went on great, not a fish anything in the part. I’m really leaning towards two theories, not reducing and not doing a thorough enough job of dry spraying before switching to a wet coat. The next part will tell. May do it as an IMC next time which I understand makes spraying multiple dry coats critical.

#22

Yeh there’s no reason a regular 2k should be spraying on well and the Duratec not, so I think that would rule out any contaminants that may just be hanging around the shop. Unless it’s something silly like you just happened to use a coloured rag to wipe off your wax and grease remover before spraying the Duratec, and a white rag before spraying the 2k clear. Coloured rags often contain silicone, so this is a common source of contamination. But seems highly unlikely.

There’s certainly something strange going on though, as I simply never experience fisheyes unless I’m spraying over pinholes (which I understand are different to fisheyes, but they appear much the same way).

Just one other quick thought, do you spray the Duratec through a dedicated gun? Or more specifically, do you use a different gun to the one you spray your 2k clear through? Is there a possible contamination source there? If you use recycled gun wash at all, then these also often contain silicone which can end up being left over in the gun.

Otherwise, I’d say just leave it as a dust coat for longer. Spray a bit of overspray somewhere so you can do a touch test, make sure the coating has tacked off before moving on. If you get any of the coating coming off on your finger, give it a bit longer before moving on to wet-coats. Duratec is formulated to resist fisheyes, so it’s definitely an odd occurrence.

#23

KISS method. Don’t look to deep when the answer is right on top…:slight_smile:

I’ve had similar results in which you describ with duratec. I really do believe temp , humidity and timming is your enemy.
BTW I grew up in a pannel shop and I paint 2k almost every day.

In summer months no problem with curing times , but high humidity can cause a few issues.

But with yours you say you wait a few units before you apply next wetter coat ? At the temp’s you describ that it would be impossable to not make it fish eye if you don’t leave it long enough. It will simply melt through the first layer or mist coat and fish eye everywhere. This is why it look good for a few moments and then fish eye’s… It the time needed to melt through and then separate from a dust piont. ( pin holes are different)

With highly mirror polished 2k painted plugs with TRwax release …in low temp I’ve had to wait at least 20min+ before doing a 2nd light coat and a 3rd before doing a proper full coat. And sometimes do a small hand size test pannel to check results before proceeding to main job.

The FINGER print test is the best and only way your know that it is ready for another coat. This way you can get some consistency in " ALL " temp conditions. There has to be enough time for esters to be evaporated out of the first coats and it dries enough so the next coat doesn’t melt it.
Very similar technique to using 2K , but duratec takes longer, much longer in cool conditions to gas off due to it’s thicker viscosity and chemical make up. Chemical bond still happends along time after spraying so don’t be worried about leaving it to long 15 to 30+ is fine. ( similar as 2k).
But in those temps probably 15mins and the finger test will come up with it on your finger. You need to be able to press firmly and make a finger print but not get any on your finger. This is not a light touch , more like medium press to a bruise on you leg and make it hurt. Not hard press but not soft.
On really glossy plugs , I find doing a few lighter coats , good drying time in between before I move on to the filler coats I have no probs.

Cheers

Tim

#24

Should make a habit of using wax and grease remover/prepsol with all spray jobs on any material. Saves doing things twice.

#25

All great stuff, thanks very much. I am going with the rushing the subsequent coats, I didn’t wait near that long, the info from Duratec says 2-3 minutes I think. I will change that and do a spray out panel along side my work so I am sure.

Thanks a lot all!

#26

What shelf life does Duratec have?

#27

1 year for the clear coat, 6 months for the primers. Substantially less if exposed to over 30 degrees, virtually indefinite if you keep it in a freezer.

KMA, give longer flash times a go, but in all honesty I think if it is taking 15-20 minutes for the Duratec to flash off then it is too cold to be spraying it. It is a polyester after all, and so much more temperature sensitive compared to an automotive 2k polyurethane. I have always used the Duratec guidelines of 2-5 minutes (2 minutes in summer, 5 minutes in winter), and I’ve never had any problems. I suspect it will work for you though, as if you are sure everything is clean then there aren’t many things that will affect adhesion.