I perform DSC, temperature -60 to 120C, of my spray dried powder sample. But i cant set the base line which transition 1 or 2 will be the glass transition temperature Tg. When i set to base line i got onset, endset and midpoint temperature. Which one is the Tg. In Gordon Taylor model, Tg, Tgs, and Tgware the glass transition temperatures of the mixture, solids, and water, respectively,xw is the mass fraction of water, and k is the Gordon-Taylor parameter, how can i predict. specially k value . my sample solid about 96% water 4%.
Mr. Isalm-the first melting peak (1) is due to melting of ice crystal whereas second one is the Tg.You can find tons of work on milk powder by Bhesh Bhandari Group and Roos group.
Hi,
1) As you have freezed you sample to -60 C, the unbound water will freeze and so when you raised your sample temperature you see an endothermic peak at -5C. so that could not be you Tg, and to make sure that your 2nd point is Tg, I would recommend you to plot a DSC graph of Reversible heat flow vs Temperature. that is the reliable plot for determining the Tg.
2) K = V2*Tg1/V1*Tg1
where V1 and V2 is the specific volume of the respective material.
For 2nd question I have attahced a paper for your referance
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