Optimization of instrument response and resolution of standard- and high-speed power compensation DSC |
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Authors: | M F J Pijpers V B F Mathot |
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Institution: | (1) SciTe, Ridder Vosstraat 6, 6162 AX Geleen, The Netherlands;(2) Laboratory of Macromolecular Structural Chemistry, Division of Molecular and Nanomaterials, Department of Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200F, 3001 Heverlee, Belgium |
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Abstract: | Normally, for Standard DSC, the PerkinElmer power-compensation setting is the low dynamic range mode (LDRM). In this mode,
a noise filter is applied to decrease the noise-to-signal ratio, which concomitantly gives rise to a delay in time of the
signal measured. In case the signal is expected to be of high intensity — experienced for instance at high scan rates using
High Performance DSC (HPer DSC) — the noise filtering could be diminished by which the associated delay in time would be less,
leading to a faster response of the instrument, also resulting in an improved resolution. In fact, such can be realized using
the faster noise filter of the high dynamic range mode (HDRM) available for the Pyris 1 and Diamond DSCs, which DSCs are both
equipped with the HyperDSCTM technique (HyperDSC being the commercial version of HPer DSC). The improvement in response is maximal for high rates like
100–500°C min−1 but even at low rates like 10°C min−1 it is still significant. Thus, taking advantage of HDRM, low-molar substances like indium and 4,4′-azoxyanisole show appreciable
increasing height-to-width ratios for signals caused by crystallization, melting and the crystal <>liquid crystal transition
respectively. Another advantage, the faster realization of steady state after the starting of the DSC, is of help in case
of overlapping starting and transition signals during dynamic crystallization and melting, and during isothermal crystallization
as elucidated for a HDPE. For 4,4′-azoxyanisole and for an ethylene-propylene copolymer having a broad melting range, it is
shown that such faster response leads to a still better resolution with respect to temperature, even at high scan rates.
Thus, the peaks belonging to the crystal-to-liquid crystal and the liquid crystal-to-isotropic liquid transitions of 4,4′-azoxyanisole
were completely resolved while a thermal fractionation of the copolymer by the successive self-nucleation and annealing (SSA)
technique with good resolution has been realized, both using rates as high as 200°C min−1. |
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Keywords: | annealing cooling rate crystallization fast scanning rate heating rate high performance DSC (HPer DSC) high-speed calorimetry HyperDSCTM melting noise filter power compensation resolution sensitivity thermal fractionation thermal lag |
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