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Please develop an archival PLA surface finish that prevents moisture resorbtion

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Hi Ultimaker materials whizz-kids,

My experiments with Krylon, CrystalKote etc have all resulted in a PLA-reactive white patina (like fog on a window) on parts of the print which spoils the PLA color.

I would love it if a non-reactive spray/paint product could be developed that would extend PLA's life and protect against moisture resorbtion. Example: an Ultimaker robot or Thingiverse truck left in an outdoor sandpit.

One thing I have not tried yet is coating the print with diluted beeswax. However, Monsanto are doing a pretty good job in eradicating bee colonies with their neocotinoid inecticides.

I've searched throughout New Zealand and there is nothing available.

Thanks!

Edited by Guest

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I take it you are trying to coat your prints without paint or primer....just  raw plastic.

Have you tried a polyurethane? It may be non-reactive. It can come in spray and liquid brush-on.

Also, try an acrylic spray. Or, even try a brush-on gel medium like this. It is acrylic based and have used it a lot when doing acrylic paintings. And, acrylics are just a plastic, so......

Anything with an acetone type of chemical in it for binding (like Krylon) will react to plastics to some degree.

I am not sure what Crystal Kote is made of so, no idea there and I looked it up and all I could find was descriptions of purpose and not content.

Edited by Guest

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I was cleaning out a bit of PVA from some soaking parts and thought about this:

Have you tried model clear coats (Acrylics, enamels and lacquers)? Things like Testor's or Tamiya, etc.?

I ask because they are formulated to work on plastics.

I am going to dig out some old PLA prints that are trash and do some testing. But, beware that I am not using the same PLA as you.

I am using a variety, some to test with (Beer waste PLA for instance because of the caramel color) and PLA/PHA hybrids, etc.

But, I will let you know what I find tomorrow after I wake up and make an appointment or two.

Edited by Guest

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I take it you are trying to coat your prints without paint or primer....just  raw plastic...

Hi kman - yes, the simplest and fastest way for me at the moment is just spraying or painting a protective coating directly on the print. I had assumed the art-shop brands such as Crystal Kote were polyurethane. All the spray cans I have don't tell you what's in them!

I've emailed Crystal Kote and Krylon to ask them about this. I'll let you know what they say. I haven't tried any model clear coats or paints.

Currently I have a small stock of Wanhao filaments in different colors and one roll of Ultimaker Silver that came with the UM2+. I would buy more Ultimaker filament but it's 3 times more expensive than Wanhao in NZ, plus 15% gst plus freight.

What benefits one gets with expensive Ultimaker PLA over the other brands is so far unknown to me. Have a look if you like at www.mindkits.co.nz (who mostly sell ultimaker stuff).

I often feel Ultimaker are shooting themselves in the foot by using the filament pricing strategy they do. Filaments are the lifeblood of 3D printing.

Edited by Guest

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This is the reply I received from Krylon:

 

I don't know of anything specific that would work for that application.  You could test the Preserve It Digital Photo and Paper Protectant in a small area:  

http://www.krylon.com/products/preserve-it-digital-photo-paper-protectant/

On that note, they say "test it" for all the spray products they sell. But I have to buy it to test it. Not exactly a winning strategy. I suggested to them that their product development team test it. PLA is not hard to source.

Edited by Guest

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Do you spray it with an airbrush, or do you use spray cans? In both cases, could it be that the paint is dilluted with solvents, and that these solvents cause the problem? A bit similar to the "acetone smoothing" that cloakfiend uses for his models, which also causes whitening, but then in this case as an undesired side-effect?

If so, manually brushing on a varnish might improve things? But these still contain solvents, I think...

Anyway, for outdoor use you would definitely need an UV-absorbing and resistant paint or cover.

Printing the model in 3D, or printing a mould, and then casting in plaster, cement (for statues), or UV-resistent PU (for toys and tools), might also be an option?

Edit: forgot to say: the most UV- and weather resistant varnishes and paints available here in Europe, are yacht and ship paints and varnishes. But I have no idea if they work on PLA.

Edited by Guest

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If you want to coat PLA, avoid laquers or paints that use ethyl acetate as the solvent, since this will react a bit with the PLA, this is possibly the source of the white "fog" you are seeing. Acetone can also cause a similar reaction, and Dichloromethane actually melts PLA.

 

It seems like the Krylon UV Resistant Clear coat spray is 41% acetone, and Crystal Kote is 10-30% Dichloromethane, so these are not really good alternatives.

 

You can try the Krylon Low-Odour or the Krylon Kamar Varnish, from the MSDS it seems like these could work. 

 

Or first coat the PLA piece with a clear plastic primer as a protective layer and then apply the UV resistant clear coat on top.

 

Edited by meduza

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I just tried some really, really cool paint. May be worth looking into. It is an automotive paint, but it really does well on PLA. And, if you are using flat colors, this would be perfect as it has a unique color sheen and is glossy.

 

Really cool stuff.....It is Dupli-Color Metal Cast Anodized paints. Make sure you get the base ground color as the anodized colors are transparent and allow the aluminum paint show through.

 

Here is a link to Amazon's listing

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