I am using polymeric binder of different molecular weight for silicon now. In the Oscillation amplitude sweep of slurries. I found a strange behavior. For lower M.wt. binder I got a yield point and storage modulus(G') was higher than loss modulus(G''). For higher M.wt. binder, there was no cross over point and G'' was higher than G'. What I expected was the other way around. How to infer this data? any literature will be very helpful. Thanks in advance.
Hello Raam,
as the Mw incread the sample behaves more like a fluid (Higher G"), the binder with high Mw reduced the elasticity of the slicon sample. I think the binder have used has high G" and its G" increases with increasing Mw, which conseqently supressed elasticity G' of the sillicon sample.
Please see attached files and links which I think would be helpful
http://www.wee-solve.de/en/amplitude-sweep.html
http://www.wee-solve.de/en/frequency-sweep.html
Regards
Amin
The rheological behavior which is opposite to what you expect is stemming from the nature of the system that is produced during the preparation of the slurries. When you prepare the slurry with the low molecular weight polymeric binder, the stresses that are generated during the mixing process are not high enough to break down the existing agglomerates and at times even assist in forming new ones. When systems with agglomerates are tested in oscillatory shear, yield stress is observed because the system behaves more solid like (hence higher G’) and needs a certain minimum stress before it begins to deform. On the other hand, when you prepare the slurry with the high molecular weight polymeric binder, the stresses generated would break down existing agglomerates, thereby giving a more uniform dispersion. It is known that for the same level of filler loading, a uniformly dispersed system would show lower levels of storage and loss moduli. There is detailed discussion on preparation of filled systems, on the factors that are critical and their effects on rheological behavior in the book:
Aroon V. Shenoy, Rheology of Filled Polymer Systems, Kluwer Academic Publishers, Netherlands (1999).
Thank you very much for such a detailed explanation... It was very helpful.
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