Dear researchers,
In many cases, the point where G'=G'' is known as gel point. Is that true? How can I check the gel or sol states using other methods?
(I often use the small amplitude oscillatory shear measurement against frequency to determine the cross point between the storage and loss moduli).
I am looking forward your advice
Thank you very much.
Hi Minh.
Yes. In solids, the storage modulus is generally larger than the loss modulus. In liquids, the loss modulus is the larger of the two. Therefore, the crossover point where these two moduli are equal is called the gel point, as you mentioned.
Since these definitions are rheological and based on the mechanical properties of the material, your method for finding this point should also be mechanical. Especially since this point is a function of multiple variables such as temperature and frequency. So, while I'm not sure what you mean by other methods, you need to use an instrument that measures the rheological state of the material, such as a DMA or a rheometer.
Dear Dr. Siavash Sarrafan . Thank you very much. I think so. I also checked the gel point using the temperature sweep and oscillation sweep by a rheometer. Thank you for your comments.
Absolutely!
Also, remember that when a material is at gel-point temperature, the storage modulus, loss modulus, and tan delta don't change much with frequency. This is not the case for liquids and solids - meaning you can also use three plots showing how these three properties change with frequency to demonstrate you're in a gel-like state.
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