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| Dulcamara... |
 Posted: Mon Oct 26, 2009 7:37 am |
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Guest
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Hello to all, i tried to obtain a dilatant fluid (http://
en.wikipedia.org/wiki/Dilatant), mixing Polyetilenglicole 200 and
silica nanopowder (14 nm diameter) at various concentrations. The
fluid became more and more viscous, but did not showed dilatant
characteristics. I used smaller particles than suggested (around 450
nm), supposing they was even better, having a total surface bigger of
many orders of magnitude. I suppose that my solution did not gone
because it became too viscous before showing shear thickening, what do
you think about?
Thank you for the ansers! |
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| Dulcamara... |
| Posted: Mon Oct 26, 2009 9:15 am |
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On 26 Ott, 20:52, Mark Thorson <nos... at (no spam) sonic.net> wrote:
[quote]Dulcamara wrote:
Hello to all, i tried to obtain a dilatant fluid (http://
en.wikipedia.org/wiki/Dilatant), mixing Polyetilenglicole 200 and
silica nanopowder (14 nm diameter) at various concentrations. The
fluid became more and more viscous, but did not showed dilatant
characteristics. I used smaller particles than suggested (around 450
nm), supposing they was even better, having a total surface bigger of
many orders of magnitude. I suppose that my solution did not gone
because it became too viscous before showing shear thickening, what do
you think about?
Thank you for the ansers!
For one thing, get rid of the silica. Fumed silica
forms networks that give it shear-thinning behavior,
not shear-thickening. The largest consumer of
fumed silica is the paint industry, which uses
the shear-thinning effect to eliminate brush marks
and the viscosity increase on standing to prevent
formation of a drip line at the bottom.
[/quote]
Thats true! I used Fumed silica, what kind of silica you suggest?
(there exhist grinded silica nanopowder?) |
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| Mark Thorson... |
| Posted: Mon Oct 26, 2009 1:52 pm |
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Guest
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Dulcamara wrote:
[quote]
Hello to all, i tried to obtain a dilatant fluid (http://
en.wikipedia.org/wiki/Dilatant), mixing Polyetilenglicole 200 and
silica nanopowder (14 nm diameter) at various concentrations. The
fluid became more and more viscous, but did not showed dilatant
characteristics. I used smaller particles than suggested (around 450
nm), supposing they was even better, having a total surface bigger of
many orders of magnitude. I suppose that my solution did not gone
because it became too viscous before showing shear thickening, what do
you think about?
Thank you for the ansers!
[/quote]
For one thing, get rid of the silica. Fumed silica
forms networks that give it shear-thinning behavior,
not shear-thickening. The largest consumer of
fumed silica is the paint industry, which uses
the shear-thinning effect to eliminate brush marks
and the viscosity increase on standing to prevent
formation of a drip line at the bottom. |
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| Mark Thorson... |
| Posted: Mon Oct 26, 2009 5:45 pm |
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Guest
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Dulcamara wrote:
[quote]
Thats true! I used Fumed silica, what kind of silica you suggest?
(there exhist grinded silica nanopowder?)
[/quote]
I'd go for a precipitated spherical silica
with a much larger particle size (>10 um).
I'd recommend Tokuyama for that. Great
company, very easy to deal with, which is
somewhat unusual for a Japanese company.
http://www.tokuyama-a.com/
I'd also recommend using a mixture of large
and small spheres, the latter to fill the
interstitial spaces between the large spheres.
You probably don't want to use crushed,
angular particles, except for the purpose of
helping keep the spherical particles in
suspension. If you don't need them, don't
use them.
There's a good discussion of filler particle
packing in _Handbook_of_Fillers_for_Plastics_
by Katz and Milewski. You should read that
before designing your next experiment. |
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