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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 935-954 
    ISSN: 1572-8943
    Keywords: calorimetry ; dielectric ; glass transition ; modulated DSC ; polymers ; relaxation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The results from temperature modulated DSC in the glass transition region of amorphous and semicrystalline polymers are described with the linear response approach. The real and the imaginary part of the complex heat capacity are discussed. The findings are compared with those of dielectric spectroscopy. The frequency dependent glass transition temperature can be fitted with a VFT-equation. The transition frequencies are decreased by 0.5 to 1 orders of magnitude compared to dielectric measurements. Cooling rates from standard DSC are transformed into frequencies. The glass transition temperatures are also approximated by the VFT-fit from the temperature modulated measurements. The differences in the shape of the curves from amorphous and semicrystalline samples are discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 50 (1997), S. 547-558 
    ISSN: 1572-8943
    Keywords: indium ; melting ; temperature calibration ; TMDSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The melting and crystallization of a sharply melting standard has been explored for the calibration of temperature-modulated differential scanning calorimetry, TMDSC. Modulated temperature and heat flow have been followed during melting and crystallization of indium. It is observed that indium does not supercool as long as crystal nuclei remain in the sample when analyzing quasi-isothermally with a small modulation amplitude. For standard differential scanning calorimetry, DSC, the melting and crystallization temperatures of indium are sufficiently different not to permit its use for calibration on cooling, unless special analysis modes are applied. For TMDSC with an underlying heating rate of 0.2 K min−1 and a modulation amplitude of 0.5–1.5 K at periods of 30–90 s, the extrapolated onsets of melting and freezing were within 0.1 K of the known melting temperature of indium. Further work is needed to separate the effects originating from loss of steady state between sample and sensor on the one hand and from supercooling on the other.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 1013-1026 
    ISSN: 1572-8943
    Keywords: activation energy ; calorimetry ; glass transition ; heat capacity ; heat flow calorimeter ; hole theory ; irreversible thermodynamics ; TMDSC ; modulated calorimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Temperature-modulated differential scanning calorimetry (TMDSC) is based on heat flow and represents a linear system for the measurement of heat capacity. As long as the measurements are carried out close to steady state and only a negligible temperature gradient exists within the sample, quantitative data can be gathered as a function of modulation frequency. Applied to the glass transition, such measurements permit the determination the kinetic parameters of the material. Based on either the hole theory of liquids or irreversible thermodynamics, the necessary equations are derived to describe the apparent heat capacity as a function of frequency.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 1081-1088 
    ISSN: 1572-8943
    Keywords: asymmetry correction ; calibration ; heat flux calorimeter ; heat capacity ; power compensated calorimeter ; temperature modulated differential scanning calorimetry ; TMDSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The quality of measurement of heat capacity by differential scanning calorimetry (DSC) is based on the symmetry of the twin calorimeters. This symmetry is of particular importance for the temperature-modulated DSC (TMDSC) since positive and negative deviations from symmetry cannot be distinguished in the most popular analysis methods. Three different DSC instruments capable of modulation have been calibrated for asymmetry using standard non-modulated measurements and a simple method is described that avoids potentially large errors when using the reversing heat capacity as the measured quantity. It consists of overcompensating the temperature-dependent asymmetry by increasing the mass of the sample pan.
    Type of Medium: Electronic Resource
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