Differential scanning calorimetry (DSC) of semicrystalline polymers |
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Authors: | C Schick |
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Institution: | (1) Institute of Physics, University of Rostock, Wismarsche Str. 43-45, 18051 Rostock, Germany |
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Abstract: | Differential scanning calorimetry (DSC) is an effective analytical tool to characterize the physical properties of a polymer.
DSC enables determination of melting, crystallization, and mesomorphic transition temperatures, and the corresponding enthalpy
and entropy changes, and characterization of glass transition and other effects that show either changes in heat capacity
or a latent heat. Calorimetry takes a special place among other methods. In addition to its simplicity and universality, the
energy characteristics (heat capacity C
P and its integral over temperature T—enthalpy H), measured via calorimetry, have a clear physical meaning even though sometimes interpretation may be difficult. With introduction
of differential scanning calorimeters (DSC) in the early 1960s calorimetry became a standard tool in polymer science. The
advantage of DSC compared with other calorimetric techniques lies in the broad dynamic range regarding heating and cooling
rates, including isothermal and temperature-modulated operation. Today 12 orders of magnitude in scanning rate can be covered
by combining different types of DSCs. Rates as low as 1 μK s−1 are possible and at the other extreme heating and cooling at 1 MK s−1 and higher is possible. The broad dynamic range is especially of interest for semicrystalline polymers because they are commonly
far from equilibrium and phase transitions are strongly time (rate) dependent. Nevertheless, there are still several unsolved
problems regarding calorimetry of polymers. I try to address a few of these, for example determination of baseline heat capacity,
which is related to the problem of crystallinity determination by DSC, or the occurrence of multiple melting peaks. Possible
solutions by using advanced calorimetric techniques, for example fast scanning and high frequency AC (temperature-modulated)
calorimetry are discussed. |
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