Can you please help me to explain each event on this DSC curve.
I suppose these peaks are due to the following reasons:
1. The first exothermic peak on the cooling curve is when crystallization appears.
2. The first little peak on the heating curve (I attached the second picture to illustrate it closer as it's intensity is very low) is glass transition. But can be a glass transition peak so weak?
I wonder if I used a correct procedure for the determination of Tg.
3. The second peak on the heating curve is melting.
Where is an eutectic temperature on this curve? I believe it is a big second peak on the heating curve, but I'm not sure.
Sample: protein solution 50 µl
Reference: empty pan
Here is my procedure:
Initial heat flow: 20 mV
1) Hold for 1.0 min at 20.00°C
2) Cool from 20.00°C to -40.00°C at 5.00°C/min
3) Hold for 1.0 min at -40.00°C
4) Heat from -40.00°C to 20.00°C at 5.00°C/min
5) Hold for 1.0 min at 20.00°C
Hi
You are correct.
The first smal peak is Tg.
The scond one is crystallization
The third one is oxidation and the next one is melting....
Best
Drear Elizaveta Belova,
According to my knowledge, your hypothesis about the peaks is totally true.
But, in order to respond to your question about weak Tg area, it should be mentioned that having low heat rate (as you mentioned =5.00°C/min) can lead to weaker Tg region.
I recommend you to check fig.5 in following address:
https://www.labcompare.com/10-Featured-Articles/352511-What-Do-Polymers-Pharmaceuticals-Foods-Metals-and-Ceramics-Have-in-Common-Differential-Scanning-Calorimetry/
Your sincerely
Hi,
All of your assumptions regarding the peaks are correct. To get larger Tg peak you need to heat the sample with higher scanning rate.
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