We would like to make such an solution that will contain colloidal silica with frit. Frit is highly insoluble to the colloidal silica. So we are in search of such a chemical (by means of dispersant) or electrical (external emf for charge balancing if possible) way that would help in this regard.
it is possible to use polystyreneulfonic acid, polyvinyl alcohol, to deflocculate frit.
Dear Sir,
Do you mean 4- styrenesulfonic acid? Can we use this acid as an de-flocculant?
Regards,
This means that the vinyl and sulphonic groups are located in the benzene ring against each other, i. е. In position 4. Try to use. Do not forget that this is an acid. It will react with your oxides. This can lead to good. But can time. It is necessary to look. To select concentration.
You can use any anionic polymer dispersants to deflocculate the frit, e.g. Na+ (or NH4+) salt of polymethacrylic acid. it can provide with electrostatic interaction (increase the surface negative charge, and away IEP poiont of the powder) and steric interaction between the particle surface--to dispersing the powers.
Chuanping,
Thank you for your responses. Can I use sodium polymethacrylate (available as Darvan 7N in the market)?
Regards,
You can use Darvan 7N if sodium ion is not an issue. If the particle size is small (
You may possibly want to check this discussion for possibly helpful references: https://www.researchgate.net/post/Slip_cast_of_fused_silica_too_much_shrinkage_after_drying_in_plaster_mold_Any_idea_about_how_to_control_the_shrinkage
'Frit is highly insoluble to the colloidal silica. ' Frit is insoluble in water!
Not sure I understand your question well. It seems to me that you wonder about the fast settling of the frit particles - micron sized or larger? According to Stokes law they cannot do otherwise. The only way is substantially increasing viscosity or microgravity.
Dear Mr. Titus Sobisch,
Right you are! The quick deposition of frit into the lq media leads to lot of problem. I will surely try your solution by making the media more viscous.
Regards,
Dey, You are talking about colloids or dispersions. None of these is a solution.
The smaller the particles (below 1 micrometer) the larger the surface area and the stronger the colloids laws. These sols are hydrophobic so by nature unstable in aqueous systems. You can stabilize the dispersion by using ions (cationic, anionic simple ions) so as to increase the zeta potential outside of the instability region (DLVO theory Derjaguin Landau Verwey Overbeek nobels) also by surface active agents but following my experience the best to use is polymers. Here again you have the option of ionic like the polystyreneulfonic acid reccomended by Yuri (there are cationic and anionic) and nonionic that are more independent of pH values like polyvinyl alcohol. These two, the fritt and silica are,almost for sure, negative (i.e. negative particles or negative zeta potential) so increasing this negative charge will improve your dispersibility. Turning the surface into a hydrofilic one will function very good too (for example with proteins, see colloidal gold prepared about a century ago still stable). It depends on what you will do next. Sodium containing systems will leave a residue, ammonium will not. Getting rid of polymers (which include simple gelatin) might be somewhat troblesome.
If you have not colloids but dispersions because of particles sizes above a few micrometers then follow Titus advice.
There are plenty of theoretical and practical books that could be of interest. The old but still good such as Arthur w Adamson´s text on colloids, The Robert Hunter on the same topic, Paul C. Hiemenz, The old but simple Duncan J. Shaw introduction to colloid and surface chemistry.
Good luck with your work.
Edgar Delgado-Mejía
Universidad nacional de Colombia
Bogotá, Colombia
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