[theresinman]

I want to improve my 3D printer resin for better light absorption.

I am trying to mix dye into a premade 3D printing resin made of approx. 50% urethane acrylate and 50% Bisphenol A Polyethylene Glycol Diether Diacrylate.

The dye is to strengthen UV light absorption, so the light bleeds less deep into the liquid resin, allowing for finer details on the Z axis.

I selected Tartrazine as a dye, as its absorption spectrum is perfect for this and easily and cheaply available, while also being not really toxic.

I know of studies that successfully used Sudan I in PEGDA resin for detail improvement, and as Sudan I is also a water-soluble azo dye, I thought I can use Tartrazine just like that. The studies don't tell how exactly Sudan I was put into the solution.

I tried dissolving my Tartrazine powder in water and glycerol, which worked but both didn't mix with my resin. Tartrazine directly into resin didn't work either and left a lot of powder undissolved.

Now my question is, how can I dissolve my dye in the resin?
Is there another good medium that is polar and nonpolar on different sides so it works as an "adapter"?

I don't know enough about chemistry to find something like that which is also easily available.
Sorry if my question is a bit basic, I really appreciate your help pointing me in the right direction.

I need about 0.5% dye content by weight in the end.

Thank you so much!

Edit: I wanted to add, that I don't just use PEGDA as a resin because it's super expensive and availability is bad in my country if you are a private person and not a lab.

[rolnor]

Can you use something without water? Small amount of ethanol or methanol? Or butanol?

[billnotgatez]

Just some links to aid in the discussion

from WIKI
https://en.wikipedia.org/wiki/Tartrazine

Properties
Chemical formula   C16H9N4Na3O9S2
Molar mass   534.36 g/mol
Solubility in water   20 g/100 mL
Solubility   18 g/100 mL in glycerol, negligible in ethanol

IUPAC name
Trisodium 5-hydroxy-1-(4-sulfonatophenyl)-4-[(E)-(4-sulfonatophenyl)diazenyl]-1H-pyrazole-3-carboxylate
Other names
FD&C Yellow 5


from PubChem
https://pubchem.ncbi.nlm.nih.gov/compound/Tartrazine
3.2.4Solubility   HelpNew Window
less than 1 mg/mL at 70° F (NTP, 1992)

National Toxicology Program, Institute of Environmental Health Sciences, National Institutes of Health (NTP). 1992. National Toxicology Program Chemical Repository Database. Research Triangle Park, North Carolina.
CAMEO Chemicals
In water, 20.0 g/100 mL at 25 °C (2.0X10+5 mg/L)

Marmion D; Kirk-Othmer Encyclopedia of Chemical Technology. (2001). New York, NY: John Wiley & Sons; Colorants for Foods. Online Posting Date: September 14, 2007
Hazardous Substances Data Bank (HSDB)
In glycerol, 18.0 g/100 mL at 25 °C; in propylene glycol, 7.0 g/100 mL at 25 °C

Marmion D; Kirk-Othmer Encyclopedia of Chemical Technology. (2001). New York, NY: John Wiley & Sons; Colorants for Foods. Online Posting Date: September 14, 2007
Hazardous Substances Data Bank (HSDB)
In ethanol, 0.8 mg/mL; in ethylene glycol monomethyl ether, 20 mg/mL

Green FJ; p. 678 in The Sigma-Aldrich Handbook of Stains, Dyes, and Indicators. Milwaukee, WI: Aldrich Chem Co. (1990)
Hazardous Substances Data Bank (HSDB)
Soluble in concentrated sulfuric acid

Lewis, R.J. Sr. (ed) Sax's Dangerous Properties of Industrial Materials. 11th Edition. Wiley-Interscience, Wiley & Sons, Inc. Hoboken, NJ. 2004., p. 1753
Hazardous Substances Data Bank (HSDB)

[MOTOBALL]

I would expect Tartrazine to be soluble in liquids such as N,N-dimethylformamide (N,N-DMF), dimethyl sulfoxide (DMSO and Hexamethyl-phosphoric-triamide (HMPA).

These solvents are all water-soluble (with highish boiling points) but I do not know how/if they will interfere with the 3-D resin.

You may have to prepare the resin in the presence of the tartrazine to incorporate it.

Regards,
MOTOBALL

[theresinman]

Can you use something without water? Small amount of ethanol or methanol? Or butanol?

I tried the ethanol as well already, it doesn't mix with my resin.

I think I need to formulate my question differently.
Does anyone know of a oil-soluble dye that has an absorption spectrum roughly maximum at 400nm and is non toxic?
I had a lot of trouble finding anything matching this that is not carcinogenic. I do work clean and with gloves and even respirator, but still would prefer to have nothing that toxic in my house.

[theresinman]

I would expect Tartrazine to be soluble in liquids such as N,N-dimethylformamide (N,N-DMF), dimethyl sulfoxide (DMSO and Hexamethyl-phosphoric-triamide (HMPA).

These solvents are all water-soluble (with highish boiling points) but I do not know how/if they will interfere with the 3-D resin.

You may have to prepare the resin in the presence of the tartrazine to incorporate it.

Regards,
MOTOBALL

Thank you! I think my 3D resin and most basic resins are pretty non polar, so my difficulty is to find something soluble for that. It seems the PEGDA based resin the scientists used is pretty polar, so it was possible to dissolve the Tartrazine directly. Sadly PEGDA is way out of my budget.

[rolnor]

Methanol is a much better solvent then ethanol. But it seems your resin is very lipophilic. DMF is a good suggestion. But this is not trivial, not any dye or solvent will work. It can be a long trial and error session.