Epoxy primer spray cans

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PostPosted: Sat Feb 02, 2019 7:23 am
So local paint shop mixes epoxy primer of my choice into spray cans if I wish.

Decided for convenience to try some out, the can saids 24hrs pot life after being activated, when I threw one of the cans in the bin 3 days after being activated, out of curiosity I did a test spray, it sprayed just fine and dried fine as well. I was using this for painting bolts after being blasted at home, I have a paint booth and mixing room at work but not at home, so spray can is super convenient.

So, the question, how long can epoxy primer be mixed for before it goes off, is the time limit simply on it’s viscocity and ability to be sprayed, did the can have a longer pot life becuase it was not exposed to the elements even though it’s chemically activated

Steve

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PostPosted: Sat Feb 02, 2019 11:38 am
It depends. Temperature plays a big part as under 60 degrees and the epoxy will stop cross-linking (curing).

Epoxy can be mixed with activator and left to induce for 24 hours before spraying, some have left it 48 hours but found it begins to thicken.

Full cure can take weeks again depending upon temperature. I painted the frame on my horse trailer with epoxy using a brush. Two coats and let it set for a couple of weeks. Took a screwdriver to it just to see if I could scratch or chip it. I was difficult to even make a mark on it.
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PostPosted: Sat Feb 02, 2019 10:14 pm
Interesting, so can one manipulate that further, example activate a can of epoxy, use it for some bolts, put the can in the fridgeover night blast some more bolts, warm the can up and paint and then back in the fridge and so on?

Steve

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PostPosted: Sun Feb 03, 2019 12:29 am
I would say that is a definite, "theoretically." We fiddle with epoxy kick times with epoxy resins all the time for example. We can indeed use a refrigerator to control it somewhat. Another kind of weird thing we learned in a wooden door restoration class was that we could (again this is epoxy resins however the basics principles would be the same) set up 2 ounce mixing cups with resin in the bottom and the hardener laid on top of it. It could set that way for quite some time without kicking at all. That would allow us to get a door completely laid out and ready to go.....then one guy starts hitting a mixing stick into each cup and handing them off to the guy that was "flow coating" (pouring) the mix. The entire door surface would then be one homogeneous mix of epoxy curing at the same rate. Once the instructor even mentioned that he had layered up a bunch of those cups the night before and stuck them in the fridge for safekeeping....... Epoxy anything is some strange stuff, temps play a huge roll in how it can work/kick.....
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PostPosted: Sun Feb 03, 2019 2:23 am
Sounds like it’s worth experimenting with?

Steve

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PostPosted: Sun Feb 03, 2019 10:15 am
Well, yeah, as long as it's test panels and the epoxy cures hard, that's pretty much it.....
We do testing for our wood shops so we know how much "fudge factor" there is when guys may mismix or not be within time windows on stuff. In industrial situations we've even sent panels out for destructive testing if we were offering some type of warranty/guarantee on our finished services. I'm usually not a big fan of the "home chemist" but with coatings the worst that happens is failure. Now, mixing stripping agents together, that can get you killed......
Hey, I was going to just mention something that a lot people don't realize about chemistry that uses a hardener. In most cases (not all), especially the epoxy paints/resins.....the more "mass" you have of these substances the faster they will kickoff and cure. Mix two 4 ounce batches of epoxy resin/hardener. Leave the one in the mixing cup and pour the other one out in a nacho tray (ha,ha, we get these at Sam's Club....great for spreading stuff out to work it). At normal room temps. the one in the cup can be heating up past 180 degrees within 5 to 10 minutes and be pretty darned hard within 1/2 hour. The stuff spread out in the tray is still pliable for maybe 1/2 hour or more and doesn't get hard for about 8 hours.
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PostPosted: Fri Feb 08, 2019 6:09 am
Didn’t work.

I mixed up 100mls of epoxy primer, sprayed around 30mls on some bolts, put the rest in a jar and put it into the fridge, time from mixing to fridge was about 30 minutes.

Next day, i pulled it out of the fridge and it was a firm rubber like substance, thought it would be fine if i let it warm up, 3hrs later on a 33 degree day and it’s still a solid rubber gel.

So no luck

Steve

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PostPosted: Fri Feb 08, 2019 9:52 am
Did you warm it to above 60 degrees?
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PostPosted: Sun Feb 10, 2019 12:53 am
Sure did, it was completely set, and did not change at all whilst warming up

All good, was an interesting experiment

Steve

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