I have been attempting to measure the glass transition temperature of various amorphous powders consisting of sugar/protein mixtures and have had little luck. I typically use a scanning rate of ~10k/min from ~20-220C. I have tried increasing the scanning rate to 20k/min, compacting the powder, and using temperature modulated DSC to increase sensitivity. I've attached an example mDSC scan of a protein/trehalose powder (20-220C, 2C/min, amplitude = 0.5C, period = 60seconds). I've seen a lot of publications observing Tg in similar materials (usually in the range I am scanning) and am wondering if anyone has any recommendations? Any help would be greatly appreciated!
I assume exothermic is up? I'm not an expert in this field but isn't that the glass transition visible at ~175°C? If its not, maybe try upto 300°C?
On the subject: Bellavia, G., Giuffrida, S., Cottone, G., Cupane, A., & Cordone, L. (2011). Protein thermal denaturation and matrix glass transition in different protein− trehalose− water systems. The Journal of Physical Chemistry B, 115(19), 6340-6346.
Martin Wortmann It is endo up. I didn't think the feature around 175C was Tg as the heat capacity should increase? The feature also appears in the non-reversing trace which means it is a kinetic, not Cp related event.
Unfortunately I get decomposition before 300C...
Perhaps I am interpreting something wrong but this was my initial thinking.
I will check out the source... thank you !!
Hello Nina,
If to judge from the shape of your DSC curves I would expect that glass transition occurs within the temperature range 45 - 100 C though the effect is quite week.
I am aware that the green curve shows the non-reversible component of the signal measured but the reversible component which should reflect heat capacity is somewhat strange - it suggests almost constant capacity within quite wide temperature range 25 - 180 C. BTW, theoretically glass transition belongs to reversible phenomena but one can meat the cases when the system behaves as non-reversible - reverse transition is essentially impeded.
- Badges
- Science topic
- Similar topics
- Engineering
- Materials Engineering
- Powders