Tips for Sample Preparation for DSC Measurements

Careful sample preparation guarantees reproducible and reliable DSC results. The following factors can influence a DSC measurement:

  • Pan material:
    • The pan material should feature good thermal conductivity and not interact with the sample material. Aluminum is therefore the pan material of choice in the temperature range to approx. 600°C.
    • For temperature ranges higher than that, or for samples with special requirements, pans made of materials such as platinum or platinum alloys, gold, silver, alumina, graphite, steel and quartz glass are available.
    • When determining the oxidative stability of cable sheathing, it is sometimes mandatory to employ copper pans [ASTM D3895]. Chemical reactions like curing sometimes require using mid- or high-pressure pans made of stainless steel or titanium.
       
  • Lids:
    • OIT measurements are mostly carried out in open pans; all other DSC measurements in pans with lids. Applying a lid results in a more homogeneous heat distribution in the pan. 
    • Aluminum pans with lids are usually used in cold-welded form. If the samples to be measured allow it, the lids are pierced to prevent bursting at higher temperatures.
       
  • Number of samples:
    • For DSC measurements on compact samples, a single sample specimen is ideal.
       
  • Sample shape:
    • In order to achieve good heat transfer between the sample and the pan bottom, the sample should have one surface with an area as smooth as possible which allows it to lie flat at the bottom of the pan. It is particularly easy to cut polymer granulates, for example, with the SampleCutter.
    • Overall, the sample should not be too high, in order to ensure that the bottom does not become deformed when the pan is pressed. For powders, it has been determined to be a good idea to compact these when possible.
       
  • Sample mass:
    • Most standards for the testing of polymers – such as ISO 11357, DIN 53765 and ASTM D3895 (OIT) – recommend a mass between 5 mg and 20 mg. For determination of the glass transition, it is usually recommended for the mass to be a little bit higher (10 mg to 20 mg) than for the investigation of melting and crystallization phenomena (5 mg to 10 mg).