What information do you get from a differential scanning calorimetry plot?
1 Answer
Differential scanning calorimetry (DSC) is often used to study polymers. You heat a sample and a reference at the same rate. When the sample undergoes a phase transition, a different amount heat will flow to it than to the reference to maintain both at the same temperature. You plot the difference in heat flow as a function of temperature.
MELTING:
The melting of a solid is endothermic. The extra heat flow to maintain the temperature shows up as a peak on the DSC plot.
The top of the peak is the polymer's melting temperature,
CRYSTALLIZATION:
When the sample crystallizes, less heat is required to raise the sample temperature. This shows up as a dip in the DSC plot.
The temperature at the lowest point of the dip is the polymer's crystallization temperature,
GLASS TRANSITION:
After a certain temperature, a polymer may undergo a glass transition. Its heat capacity increases. The middle of the slope represents the glass transition temperature,
A whole plot often looks something like this:
