Dear all,
Recently i ran an oscillation test using gelatin mixed with transglutaminase (conditions were 40 degree celsius, 1 Hz oscillation frequency and 1% oscillation strain) and i realized that its storage modulus were all greater than its loss modulus throughout the 30 min run. At around 1000s however the two curves crossed but after that the storage modulus remained higher than loss modulus. What is the implication or meaning of this observation? Thanks for your kind responses :)
Dear Justin Tan, yes it is possible, you have just to determine the rheological type of the liquid in question. My Regards
Dear Justin, Yes this is possible when your material contains a type of yield stress. When the stress that you apply in your oscillatory measurement is below the yield stress you are measuring properties of the network and you will find that the storage modulus is larger than the loss, hence the material is behaving close to a solid. When the stress you apply is above the yield stress you will see a cross over and a loss modulus larger than the storage modulus, indicating a more liquid behaviour. Note that it is probably easier to determine yield stress by constant stress rotational method.
It is possible, Justin. From your description, it seems to me that you were applying a constant strain rate and oscillation frequency and you were monitoring the changes in storage and loss modulus over time. As mentioned by Paul, this could be due to the fact that the yield stress of your material hadn't exceeded. You are welcome to read my recent work on yield stress measurement using oscillatory test if you wish to know more about it. The link is as follows:
Article Yield stress measurement of a thixotropic colloid
Cheers. Hope it helps.
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