While conducting the DSC tests, the result was obtained in such a way that the heat flow value is always negative for all the Tg, Tc and Tm peaks? what is the reason for the negative value for all the three peaks?
Dear Prased,
What kind of material are you testing? If your material has an exothermic process during DSC test, such as decomposition, cross-linking, crystallization or oxidation, the heat flow and dH/dt is negative. Because heat flow of the sample is lower than that of the reference. Thus, your peaks are in negative direction.
I do recommend the book 'Differential Scanning Calorimetry - An Introduction for Practitioners' where the principles of thermogram are discussed.
As it looks like, the DSC plotting is set to "exo up" mode. See manual to chsnge to "endo up" mode to get positive heat flow rates for endothermic processes (cp as well as melting and phase transitions. Good luck!
I would also first check the manual of the apparatus, and repeat the experiment on some known material, to see if everything is working well. Only then I would start looking for explanations.
so:
(1) make sure that you know how to perform the experiment
(2) use a known material fro which DSC is known and check if you obtain the same result.
(3) repeat this experiment again and show us all mentioned results.
Best, ie
No, problem. Multiply for (-1) the column of DT and that's all. Or change the configuration of your apparatous (polarity of the thermocouples).
Dear Mr. Prasad, it is natural to have endothermic reaction, at Tg and Tm for mostly used thermoplastic composites. But when Tc is concerned (I believe it as crystallization temperature), it should be exothermic one, as it may release energy, while solidifying. But i am not able to understand that while heating, how you can check it for crystallization? Also as per the curve, i believe, you are using PLA matrix composites.
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