Why is heat flow negative in DSC?

If your material has an exothermic process during DSC test, such as decomposition, cross-linking, crystallization or oxidation, the heat flow and dH/dt is negative. Because heat flow of the sample is lower than that of the reference. Thus, your peaks are in negative direction.

What is heat flow in DSC?

Heat flow rate The amount of heat that passes from one substance to another per unit of time, is the heat flow with the unit of measure Joule per second [J/s]. This is the unit of measure Watts [W] that is commonly used to indicate power.

What are endothermic and exothermic peaks in DSC?

Sample data of DSC Also, an exothermic peak is observed around 130°C, indicating an exothermic reaction caused by crystallization. The endothermic peak observed at around 250°C refers to an endothermic reaction by “melting”.

How does DSC measure heat flow?

During a change in temperature, DSC measures a heat quantity, which is radiated or absorbed excessively by the sample on the basis of a temperature difference between the sample and the reference material.

How does heating rate affect DSC?

Good agreement was found between theoretical curves and experimental indium DSC peaks. As heating rate increases, there is an increase in both peak height and the time necessary for the sample to catch up with the programmed temperature.

Is heating endothermic or exothermic?

endothermic process
Heating is an endothermic process, but not a chemical reaction.

Why TM is endothermic on the DSC thermogram?

As the temperature increases the sample eventually reaches its melting temperature (Tm). The melting process results in an endothermic peak in the DSC curve.

What are the factors affecting DSC curve?

Factors affecting DSC curve Instrumental factors: These include parameters such as – Furnace heating rate, furnace atmosphere, recording speed, geometry of sample holders, location of sensors, sensitivity of the recording system and material of the sample container.

What is the disadvantage of DSC?

Besides, DSC shows other limitations, like the reduced sample size to be measured. The dynamic nature of the technique can be also considered a drawback for certain applications, because it implies a “lack of equilibrium” conditions whereas the properties to be determined they are inherently equilibrium properties.

How does heat flow in exothermic and endothermic processes?

3: (A) In an endothermic reaction, heat flows from the surroundings into the system, decreasing the temperature of the surroundings. (B) In an exothermic reaction, heat flows from the system into the surroundings, increasing the temperature of the surroundings.