I am measuring glass transition temperature of freeze-dried maltodextrin-trehalose mixed systems. In 100% maltodextrin anhydrous systems I cannot find any step change indicative of Tg. I am scanning heating-cooling-heating from 100 degrees to 200 degrees at 5ºC/min the heating scan and 10ºC/min cooling scan and recording the Tg in the second scan. The second scan shows flat profile. On the other hand, I can spot the Tg in 20%Trehalose/80% maltodextrin at 173ºC. Some papers state the difficulty to detect Tg in anhydrous systems of high molecular weight maltodextrins. Any advice on how to perform the analysis to find the Tg?
Please check the degradation temperature via TGA and set the DSC heating rate below the degradation temperature. Then please identify the holding time either it is 1 min/ 3 min/ 5 min. Good luck!
if you can prepare pellets from your sample you may try to utilize another technique, such as TMA (thermomechanical analysis). It may work if DSC is not sensitive enough.
Rodrigo,
Depending on the dimensions of your material, there are several other techniques you could use for finding its Tg. Like Dr. Banhegyi mentioned, TMA would be a good possibility especially because of its highly sensitive LVDT module (see attached paper for its applicability). DMA is another option based on the stiffness and dimensions of your material.
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