Zeta Potential, drag and levelling.

[DrP]

When I was doing some work experience, back in the 90's, I was asked to work out the zeta potentials of particles in an industrial slurry.... I'm sure it was just an exercise to keep me busy and out of the way as I could see no practical use of knowing these potentials in the situation they had. This meant that I had to look through a microscope with a graticule, apply a charge across the sample and time how long it took for a particle to cover a certain distance - from an equation involving particle speed and charge I could work out the zeta potentials of the particles... a few dozen runs (along with the odd crafty snooze) and an average was taken.

 

 

I am currently looking at different slurry. I have an inert graphite filler in it currently and it does not level too great when it is spread. I think it levels a lot better with glass frits as a filler rather than the graphite particles. (either are interchangeable in the formulation of the slurry). I was thinking of trying to measure the zeta potentials of the graphite particles so as to compare them to those of the glass....

 

Q: Would one expect better levelling and less drag of the material during spreading if the zeta potential of the particulate filler was lower?

Q: Does anyone have any zeta potential data for graphite particles compared to glass? I cannot find any and suspect that it might be case specific, i.e. it might depend upon particle size and distribution as well as the make up of the rest of the slurry.

Q: Would we expect the zeta potentials of particulates of glass to be lower than that of graphite?

 

 

Thanks.

[studiot]

The total interaction force is a combination of the electrostatic (zeta) and the hydrostatic pressure force.

 

Water has a high surface tension, which can affect the latter, which is why surfactants are used.

These are also called plasticisers in the concrete and mortar industry.

 

The addition of such a compound may help with your flow and levelling issues.

[DrP]

Yes - thanks - we do use surfactants and I have been upping the amounts that go in over time and it does help a little. The change of material though seems to have more of an effect (there is only so much surfactant you can put in a formulation before the people that weigh the stuff out start to look at you as though you are crazy- lol).

 

I was kind of curious as to whether the drag and levelling had anything at all to do with the zeta potentials of the filler materials. It would mean I could look at a table of zeta potentials rather than randomly trial lots of different fillers.