Synthesizing Resin

You can discuss Photo-sensitive resins, polymers, and oligomers.
Mariraja
Posts: 8
Joined: Fri Sep 04, 2015 12:01 pm

Synthesizing Resin

Postby Mariraja » Mon Dec 14, 2015 7:23 pm

Hello All,

Has anyone tried adding pigments to resin?

If so what are the factors that gave you trouble and what you had to understand to solve the problem?

Regards,
Bimmer

raw
Posts: 12
Joined: Tue Jul 28, 2015 12:28 pm

Re: Synthesizing Resin

Postby raw » Sat Jan 09, 2016 3:54 pm

we have!

http://discourse.materialsgirl.co/t/add ... r-resin/94

a few things to consider:
1) a little pigment goes a long way
2) the pigment needs to be compatible with your curing chemistry. (ie, if it reacts with radicals it'll slow down the cure)

jkao
Posts: 45
Joined: Sun Jan 04, 2015 5:42 am

Re: Synthesizing Resin

Postby jkao » Sat Jan 09, 2016 4:56 pm

Nice work! I'm glad that you tried iron oxide, I have some that I haven't used yet. I was concerned that iron oxide is an oxidizer and could trigger polymerization, it's good to see that it's usable.

I've tried quite a lot of pigments, the easiest to use so far has been pre-mixed pigment paste from TAP Plastics (http://www.tapplastics.com/product/fibe ... igments/50), although I've also tried 5 micron aluminum powder, carbon black, nano-zinc suspension (commercial sample), and mica powders.

There are two main concerns that I've found with pigment:

(1) Material property changes in the resulting print (mainly the print being softer and weaker when pigment concentration gets in the >0.5% range)

(2) Settling of the pigment powders

Generally speaking, issues with material property changes can be controlled by carefully measuring with an accurate 0.01g scale. You don't need that much pigment to make a resin completely opaque, but you need to be aware that you can add more pigment in but cannot take pigment out.

Settling issues can vary depending on the types of resins you are using. Form 1 resins tend to be more viscous formulations, and so pigments settle more slowly. However, you do need to be aware that everything is well mixed all the time.

I use a Kudo3D Titan 1 DLP printer, and this printer performs much better with less viscous resins. Pigments may show signs of settling in as little as 30 minutes in low viscosity resin and you would need to stir what's in the vat periodically if you didn't do something to try to control settling.

There are a lot of options for controlling pigment settling, but none of them are perfect. Finer pigments settle much more slowly. For instance, the non-sized zinc suspension is an 80 nm (0.08 micron) particle size and has no apparent settling in time scales < 1 week. Carbon black and mica powders don't come with a very precise particle size and tend to vary from 0.1 to 10 microns. Some of these settle very fast. 5 micron aluminum powder is more accurately sized (this stuff is sold generally for pyrotechnic use and since particle size affects speed of explosion reaction, buyers really care that the advertised particle size is accurate) and has no noticeable settling in < 1 day.

Pigment blends can come with various dispersion enhancing agents designed to help keep pigments in suspension. They generally fall in the category of deflocculating (clump-preventing) agents and controlled flocculating (hold the particles together in a structure so they don't move) agents. Some more advanced pigments like ColorCon pigments come in liquid suspensions that contain such agents.

You can also try to control settling by altering the properties of the resin itself. What we typically might call a "thick" liquid actually has two separate effects. Viscosity is how runny the liquid is, and thixotropism is how much motion is necessary to get the liquid to begin flowing. Most resin fillers affect both properties, but at different rates. For example, cabosil (fumed silica) is commonly used to thicken epoxy, polyester, and polyurethane resins to bring them to a putty-like consistency. However, in lower concentrations, it begins to increase thixotropism before it significantly increases viscosity. For systems that perform better with low viscosity resin, this is useful since pigment settling can be controlled by making the resin more thixotropic while trying to keep viscosity low. I've gotten good results with around 0.5-1% cabosil by weight to reduce settling (perhaps doubling or tripling settling time) without significantly increasing viscosity.

I do, however, also like dyes quite a lot since they keep the resin transparent and dissolve into the resin, and thus do not settle at all.

The CastinCraft dyes that TAP Plastics sells are, unfortunately, pretty crappy for 3D printing purposes because the concentration of dye in those is very low (0.5-1%). I do like aniline dye powders (I've found that alcohol soluble types can dissolve directly into many resins, although a bit of glycol ether makes everything much easier) and TransTint wood dyes, which contain metal complex dyes pre-dissolved in glycol ether in 20-50% concentration depending on color. Both of these dyes can provide light blocking (depth/detail control) for pigment/UV blocker free resin formulations and give a lot of color control. For aniline dyes about 0.025% weight/volume or less works (get a milligram scale), and for TransTint, about 2-6 drops per 100mL resin.

raw
Posts: 12
Joined: Tue Jul 28, 2015 12:28 pm

Re: Synthesizing Resin

Postby raw » Sat Jan 09, 2016 5:22 pm

Lot's of great tips here, thank you for sharing!

Mariraja
Posts: 8
Joined: Fri Sep 04, 2015 12:01 pm

Re: Synthesizing Resin

Postby Mariraja » Wed Feb 24, 2016 12:58 am

Thanks a lot for the tips. With the inputs you guys gave I was able to dissolve a nano material in the resin and successfully print parts out of it. The printed part is displayed in the following link http://mariraja-ponraj.format.com/addit ... uring#e-10. Having my fingers crossed because I have not tested the strength of it. Planning to do Hardness testing in order to confirm any improvement in strength.

jkao
Posts: 45
Joined: Sun Jan 04, 2015 5:42 am

Re: Synthesizing Resin

Postby jkao » Wed Feb 24, 2016 4:37 pm

Cool! Can you tell us what pigment you eventually used and what resin you dispersed it into?

I"m particularly interested in your mention of "carbon allotrope" in the your photos, although that description seems somewhat generic since carbon forms many allotropes (e.g. diamond is an allotrope, a carbon nanotube is a different allotrope, as are buckyballs, graphite, etc...)


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