I prepared emulsion of (silicone oil 5cSt + water + triton 100X) and I measured the dynamic viscosity using a rotational rheometer and the emulsion shows shear thinning behavior. However, when I tried to prove this behavior by taking the pressure drop measurements using a pressure sensor along microchannels, and apply power law, I got the power coefficient approximately ~1, which is Newtonian behavior. Has anyone worked on a related topic?
Dear Mekidelawit Girma,
Which type of rotational rheometer was used?
I suggest to use cone on plate rheometer for that.
Regards,
Akram
Dear Mekidelawit Girma,
You are welcome.
Could you give me some details about your experiment, especially the condition and the parameters that were used in your work, such as shear rate and speed ranges, temperature, cone size, and so on?
Regards,
Akram
You have emulsion, you have tiny tiny particles or droplets (O/W or W/O) in your continuous phase, with that crazy X100 molecules that adsorb everywhere. There is a Halloween party going on in your system. Push your friend in an empty classroom, they will move 2 m, push them in a crazy party like you have in your beaker, they will move 0.1 m. There will be interaction between all attendees in this party, like there is in your party in the beaker. You have a correct measurement with that disc! There will be interaction between the disc, and all these bodies in your emulsion system along with interaction between them in the continuous phase. you give the system an energy and the interaction between all these people in your system will take some of that energy. This is what you are seeing as shear thinning behavior. You cannot represent all these interactions in that pressure drop experiment.
I would even say, if you want to normalize your viscosity against all these craziness, use kinematic viscosity!
Good luck!
Hi Akram!
The temperature was 25deg. For rheometer measurement, the shear rate ranges from 1~2000[1/s]. In pressure drop measurement, I calculated the corresponding flowrate from the shear rate values and used a syringe pump. Cone ( Diameter = 50mm and cone angle 1deg)
Thank you Bahzad Vaziri Hassas,
I like the party example :)
But I still wonder, why the emulsion didn't show shear-thinning behavior since there is still interaction in the microchannels. Actually, I tried to characterize the shear-thinning behavior of the Xanthan-gum solution using rheometer and pressure drop measurements. And unlike the emulsion, the results from both approaches agreed well.
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