I'm going to make a suspension of Carbon black in order to mix it with another water base suspension and freeze-dry it. considering the point that carbon black does not mix with water properly I need to use another solvent. I tried DMAc but my sample melted during freeze-drying!!! I'm wondering what would be the best option?
Thanks
Dear Rassoul,
There are relatively few organic solvents that will freeze dry well - DiMethyl Acetamide is not one of them! It may be used for inks, but not freeze drying. Things like tert butanol, water, 1,4-dioxane, cyclohexane freeze dry well. DMSO can be used, but the risk here is having a suitable system for working with agressive organic solvents is the challenge (this is also true for DMAc.) as most dryers are made for water ...
To disperse the carbon black you will need a whetting agent in there, and you need to generate some viscosity in the mix to help it disperse well using a high sheer mixer. It is unlikely from my ancient knowledge of whetting agents (I'm not up to date) that these will not evaporate but will remain behind in the carbon black. Typically carbon black is dispersed into oils, not things that freeze dry well.
Do you really need to freeze dry? Is this the correct process?
Kind regards
Rob
It might be good to activate CB surface with a pre-process step (Acid or Piranha solutions, not sure) under stirring.
KR, Nabyl
you may be use a methanol water mixture and decrease the pH of the solution a bit, or try to functionalize the carbon black with an carboxilic acid
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