Thermal analysis is a method to accurately record the relationship between the physicochemical properties of a substance and its temperature under programmed temperature control, and to study the physical changes such as crystalline transformation, melting, evaporation, dehydration, or chemical changes such as thermal decomposition, oxidation, and the accompanying changes in temperature, energy, or weight that occur during the heat process.
In conducting thermal analysis experiments, how much sample volume should be taken for the experiment? What is the effect of a large or small sample size on the experimental results?
- A) Small weight of sample: reduce the temperature gradient in the sample, the measured characteristic temperature is lower and more “realistic”; facilitate the diffusion of gas products and make the chemical equilibrium develop in the positive direction; the separation ability of adjacent peaks (platforms) is enhanced, but the DSC peak shape is also smaller.
- B) Large weight ofsample: it can increase the DSC detection signal, which is good for detecting small heat changes, but the peak shape widens, the peak temperature drifts to high temperature, the adjacent peaks (platforms) tend to merge together, and the peak separation ability decreases; and the temperature gradient in the sample is larger, and the diffusion of gas products is also slightly worse.
Generally, if the sensitivity of DSC and thermal balance is sufficient, a smaller sample size is appropriate. In general, the common sample size for thermal analysis is 5 to 15 mg.
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