Bubble when doming badges

[Jovan Djokic]

Hi all.

I use various laser plastics for engraving name badges (IPI, Rowmark, Trolase etc.) and I'm having some issues with bubbles sometimes (not always) appearing on the badges when I leave them to dry overnight.

I use a 2-composite resin that is applied to the badges through a doming gun (so the mixture is evenly mixed and spread).  After I apply, I check for bubbles, remove any with a lighter and once I'm sure there are no bubbles I cover the domed badges with a plastic box/lid and leave them to dry and harden. In the morning when I inspect them, I sometimes get badges that have overnight developed a large number of tiny bubble on the surface of the badge and even on occassion a badge may have a whole eruption of bubbles on the surface as seen on the attached photo.

Why does this happen, considering I check and make sure there are no bubbles at all after I have domed them?  How and why do these bubble appear afterwards? Could it be the temperature in the room (it's standard room temp.), or something else that causes a delayed reaction and bubbles to appear afterwards?

If anyone has had similar outcomes and resolved them, I'd appreciate any feedback.

Thanks,
Jovan

360251

[Rodne Gold]

The problem is humidity in the air , the resins absorb moisture and bubble...
2 ways to cure this
1) dome in a moisture free area , a small dehumidifier works
2) prior to the resins gelling , use a small butane torch waved over the domed items , this allows the trapped air bubbles to rise to the surface of the resin and pop.

[Jovan Djokic]

Thanks for the suggestions Rodney. I'll look into getting a dehumidifier and see how that works out.

It's strange though that out of a batch of domed badges, only some of them (and only sometimes) get ruined by bubbles afterwards. I'm thinking that may be the material itself is at fault... maybe some laser plastics are more suited to doming than others. Have you had any such issues where changing the material resolved the bubble issue?

Thanks again for your advice.
Regards,
Jovan

[Rodne Gold]

Sometimes air gets trapped in the deeper engraved sections and then rises when doming , however material has little to do with this ..
The way you mix is also an issue sometimes with air bubbles trapped in the mix as you stir it .. but with a gun and a static mixer , this shouldnt be an issue..if it is , stick the mixed resin in a vacuum chamber to degas.
Resins with very long pot and curing times are also problematic as the long times to gel allow the resin to attract water
The type of resin is also important , epoxy resins are far less hygroscopic than polyurethanes , but the poly resins can have very short cure times , we use poly and can handle and ship domed items within hours.

[John Blazy]

I work with several types of liquid resins for my laminates, and the first thing I thought of for you would be to pour only 20% of your resin into the badge, then take a needle or toothpick and drag it inside all engraved inside corners / grooves, etc, to release any bubbles that might be stuck. then pour the rest of the resin over top.

As far as heating is concerned, I like the torch method because it works well, but any flame based heat can burn the resin, and pre-cure different monomers within the resin, and they don't manifest until cured. So I like to use a high temp heat gun, or even my plastic welder for super hot air only, no flame / soot / fuel impurities.