Hello,

We would like to use nylon to hold ink. This is part of a pen that is being 3d printed in nylon 12.

Is there a post production technique that we could use to stop the nylon absorbing the ink ?

Thanks for any pointers !  

1.  Is the 3D printing creating a porous surface, i.e. is the ink soaking into gross porosity?  You'll need a coating to fill the porosity if so, or find a way to post-sinter and hope the nylon will flow to seal the porosity.

2.  If not 1, are you using water-based ink?  Nylon likes to absorb water.  Try conditioning the nylon (soak in water for 8-24 hours, then air dry) before filling with ink.

Thanks very much for the rapid reply.

The surface is porous and the ink does soak into the gross porosity. It would be great to find a coating but I have not had any luck up until now. The ink reservoir would need to be coated using a dipping process I think.

Conditioning the nylon is certainly a good point - thanks. But I think I will still need to find a coating of some sort.   

Check with the places that offer 3D part services.  There are coatings for the PC-like materials that we have used successfully in the past (made valve models clear enough to see the water flow inside).  I believe the coatings are urethane-based, but don't know for sure.  Pat will be along soon, and may have suggestions for coatings for nylon.

Some 3D parts services will dye the parts. This is perhaps going to reduce the problem. But I am not aware of any 3D printing service offering other treatments.

I've stumbled across information related to "stain blockers for nylon" These techniques are widely use din the carpet industry.

I wonder if teflon could be applied to create a protective layer.  Teflon One Coat coud perhaps work ?

Why not make the prototype using the process where you print in molten thermoplastic as that gives a non-porous part. See for example www.stratasys.com

I have used that in the past. Standard materials for that process are ABS and polycarbonate.

Chris DeArmitt PhD FRSC CChem

The main reason we would like to use nylon is because it is one of the cheapest 3D printing materials offering a high level of definition.

On another project I got a quote from Stratasys (a few days ago) using FDM that was about 4 times higher than the quote from Shapeways using SLS.

But thanks for the suggestion.

 

Dye will color the parts, but not seal the gross porosity.

"But I am not aware of any 3D printing service offering other treatments"

Stratasys, quickparts, protomold, all offer sealing on their 3d printed parts.  I thought...maybe its only for the SLA models.  I will grant you that different technologies and substrates will react differently (and probably need different formulas) to different sealers.

The following all talk about it, but none of them have any specific suggestions beyond paints and coatings available in typical hardware stores:

http://www.fortus.com/Products/Finishing-Touch-Smoothing-Station.aspx

http://digitalcommons.utep.edu/cgi/viewcontent.cgi?article=1010&context=couri_abstracts_sum11&sei-redir=1#search=%22sealing%20FDM%22

www.cs.berkeley.edu/~sequin/TALKS/SIGG03_RP2.ppt

I'd start with a thinned urethane varnish, and move up to a thinned acrylic paint if needed.  Find finishes that use solvents that aren't included in your ink formula, would be my parting suggestion.

Nylon is quite good at absorbing dyes. That was one of the main attractions for its use in textiles. Your ink may contain dyes that work as dyes for nylon.

There are chemicals that will compete with the dyestuff and block the dye sites in the nylon. This is used at times in wool nylon carpets to help the wool and the nylon to take the dye to the same extent and match each other when dyed in the same bath. I forget their name, but dyestuff companies should be able to help.

I am not quite sure of your design and the part that is nylon.

Do you have an ink tank that is nylon then you print that, or do you have a tank that does not stain from the ink, then you print that with a nylon based ink to print on the tank, then that nylon based ink absorbs other colours from the ink in the tank.

Regards
Pat
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Sorry for the delay in my reply. I'm in France so the timezone is perhaps not helping.

The entire ink tank (including the structure of the tank) is 3D printed in nylon.

What do you think about a teflon coating - would that bond well to the nylon ?

Regards,
  Mark

OK. I get it. (slaps forehead) It's a rapid prototype not an injection moulded mass production part.

Teflon will not stick, but you might be able to mix PTEF fine powder into the nylon before it is printed. I am a bit out of date on what's available and what form the resin is in before printing the part.

You might improve the part by flame polishing.

You might improve it by painting with a clear 2 pack polyester. You will probably need a primer specifically for nylon to get good adhesion.

Why nylon. Nylons absorb colours and stain easily.

Regards
Pat
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Hi Pat, we want to use a 3D printing service, so we will not have control over the mix for the material. The choices are still fairly limited for this production technique.

The particular type of 3D printing we are looking into is SLS where very small particles are laser sintered.  

Nylon would be ideal in terms of cost vs print detail.

Regarding the PTEF I was wondering about baking Teflon S (there are low bake temperature variants)

Regards,
  Mark




 

Another angle that I hope someone can shed some light on is a polyurethane coating. This seems to be used to seal nylon for tents etc. Could this be applied in a dip process ?

I think PU also absorbs quite a few dyes so is inclined to stain. That is why I suggested polyester as it is less inclined to absorb colours.

Regards
Pat
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Yes, you could dip (or pour & dump) urethane, which is why I suggested it.  Pat's comments regarding staining from ink dyes should be considered.  2-part polyester casting resins, in a low-durometer, or better a low-viscosity, formula would be an approach if staining is an issue.

Ah yes, you did suggest a urethane varnish earlier, thanks. There I was thinking I had a brilliant idea :)

The problem of staining raised by Pat calmed my enthusiasm for the urethane.

I found a paper discussing coating nylon substrates by sol-gel I'll mention it here for completeness http://www.tandfonline.com/doi/abs/10.1080/17452759.2010.491938#preview

It is surprising to find so few coating solutions for a material that has been around for so long !
 

Things don't stick well to nylons. That is one of its advantages in many applications. It is hard to paint and speial proceduresare required to get good paint adhesion.

Re the staining of various materials, it will vary, depending on the nature of the colourants. My comments re dyes and stains are generalised. Results with specific colourants may vary from the general trend. Without going into details, it depends on the existence of particular chemical groups and polarity in the molecules of each and on pore sizes in the polymer.  

Regards
Pat
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If this is an effort to reverse engineer ink cartridges for my stupid HP printer, then more power to you.

But, at the root, making an ink container via an inherently porous process should perhaps be reconsidered.

BTW, I made some really cool containers out of some scrap nylon tubing...using commercial "RIT" dye to color it.

...oh, should've mentioned that Pat was the one who'd nudged me in that direction, I'd have never considered dye-ing nylon otherwise.  I think I gave him a star for that suggestion.  Because it was so helpful.  By "star", I mean I clicked the link at the bottom of his post, where it says "Thank Pat for his helpful post".

I agree that a change in material may be the best choice. That is looking like the conclusion. But I now have a better idea of why it is a good conclusion, thanks.

Pat, if you wouldn't mind, I'd like to understand why the Teflon S is not suitable. It seems teflon is used as a post-treatment for nylon carpets e.g. http://www.baneclene.com/catalog/teflon.html In this case it does get removed during industrial cleaning. In our application the coating is not subjected to significant abrasion - it is the chemical resistance that we need. But if the teflon is baked on I imagine that would make a much more permanent bond ?

Regards,
  Mark

I received some information from RelTek about their products :

"The B-45 and B-482 are possibilities.  You mentioned that the reservoir might need to be dipped; the two epoxies are simular viscosity to honey, which makes it fairly easy to pour into a container and dip your parts in to coat.

However, surface prep on the nylon may be required to increase surface energy and create a stronger bond.  We recommend abrading the surfaces with 100-120 grit sandpaper and clean with isopropyl alcohol.   Ideally, the adhesive coating should fall between .004'-.007' thick over the nylon, to ensure a good cross-link.   Average cure time is 24-36 hours at ambient. "

RelTek get huge credit in my book for answering so effectively.

This is looking close to a viable solution.

Glad they answered with practical advice although it sounds like they don't have full comprehension of the topic. For example surface energy is not increased by abrasion or an alcohol wash. Sanding just gives more surface area.

Chris DeArmitt PhD FRSC CChem