WärmeflussDSC

WärmeflussDSC refers to a mode of differential scanning calorimetry in which the heat flow into or out of a sample is measured as a function of time or temperature under a controlled heating or cooling program. In many German-language sources, the term corresponds to what is internationally known as heat-flow differential scanning calorimetry (HF-DSC). The technique provides information on thermal transitions and energetic changes in materials.

Principle and setup: A sample and a reference are placed in identical pans and subjected to a calibrated temperature program. The DSC instrument uses heat flux sensors or a power-compensation scheme to measure the difference in heat flow between sample and reference, producing a heat-flow signal in units such as mW or mW per mass. The signal is typically plotted as heat flow against time or temperature.

Interpretation: Endothermic and exothermic events appear as peaks or baseline shifts in the thermogram. The glass transition shows as a step change in the baseline near Tg; melting peaks indicate crystalline phase transitions; crystallization peaks indicate crystallization from the melt. Enthalpies of transition and fictive thermal properties can be derived through appropriate calibration and integration, and changes in heat capacity can be inferred from baseline regions.

Applications and advantages: HF-DSC is used in polymers, pharmaceuticals, foods, and materials science to determine thermal properties, phase behavior, crystallinity, and purity. It accommodates small sample masses and can employ fast heating rates, enabling efficient screening and detailed thermal analysis.

Limitations and notes: Accurate interpretation requires careful baseline correction, calibration, and consideration of heating/cooling rates, sample pan compatibility, and potential moisture or volatile losses that can affect the signal.