Thermochimica Acta

Items from 1 to 20 out of 22 results

article

Time dependence of the complex heat capacity at the melting temperature of polyethylene crystals

Y. Saruyama

Thermochimica Acta > 2001 > 377 > 1-2 > 151-158

Time dependence of the complex heat capacity of polyethylene crystals was measured at several temperatures between 80 and 130 ^o C using light heating modulated temperature DSC. Time dependence could be expressed as a sum of fast and slow components. The fast component had the complex value and decayed within a few minutes. On the other hand, the slow component had the real value and decreased...

article

The application of temperature-modulated DSC to the glass transition region - II. Effect of a distribution of relaxation times

J.M. Hutchinson, S. Montserrat

Thermochimica Acta > 2001 > 377 > 1-2 > 63-84

An analysis of temperature-modulated differential scanning calorimetry (TMDSC) in the glass transition region is presented. It extends an earlier and simpler model by introducing a distribution of relaxation times, characterised by a Kohlrausch-Williams-Watts (KWW) stretched exponential parameter β, in addition to the usual kinetic parameters of relaxation, namely the Tool-Narayanaswamy-Moynihan (TNM)...

article

Preface

Christoph Schick, Günther W.H. Höhne

Thermochimica Acta > 2001 > 377 > 1-2 > ix

article

Temperature-modulated differential scanning calorimetric measurements on nascent ultra-high molecular mass polyethylene

G.W.H. Höhne, L. Kurelec

Thermochimica Acta > 2001 > 377 > 1-2 > 141-150

Temperature-modulated differential scanning calorimetric (TMDSC) measurements on nascent ultra-high molecular mass polyethylene (UHMMPE) in scanning as well as quasi-isothermal mode are presented. From these measurements, a special irreversible relaxation process in the pre-melting region can be separated, which only occur on the first heating of the nascent material. The frequency dependence of this...

article

A new light driven spectrometer for the determination of complex heat capacities and conductivities by combination of effusivity and diffusivity measurements

Thomas Albrecht, Simon Armbruster, Brend Stühn, Kersten Vogel, more

Thermochimica Acta > 2001 > 377 > 1-2 > 159-172

We describe the construction, performance and first application of a spectrometer for measurements of frequency-dependent complex thermal diffusivities and effusivities. Knowledge of these quantities enables the complex dynamic specific heat and the thermal conductivity to be calculated. The technique uses the properties of thermal waves initiated at the surface of plate-like samples by the absorption...

article

Development of the front-detection photopyroelectric (FPPE) configuration for thermophysical study of glass-forming liquids

M. Chirtoc, E.H. Bentefour, C. Glorieux, J. Thoen

Thermochimica Acta > 2001 > 377 > 1-2 > 105-112

We report on the first frequency-dependent measurements of thermal effusivity of glass-forming liquids using the photopyroelectric (PPE) method. The advantage is higher modulation frequency capability than with previously reported methods. On the basis of our present results (up to 30kHz), we find in the dispersion temperature region of glycerol a clear frequency-dependence of the real part and a...

article

Enthalpy and dielectric relaxation in the glass transition region of polypropylene glycol

I.K. Moon, Y.H. Jeong, T. Furukawa

Thermochimica Acta > 2001 > 377 > 1-2 > 97-104

We investigated enthalpy and dielectric relaxation behaviors in the glass transition region of polypropylene glycol of molecular weight 1000 and 4000 by measuring both dynamic heat capacity and dielectric susceptibility as a function of frequency and temperature. The data at each temperature were fitted to the Kohlrausch-Williams-Watt (KWW) relaxation function, and the relaxation time, the shape parameter...

article

Equilibrium, nonequilibrium, and nonlinear enthalpy relaxation in a supercooled ionic liquid [Ca(NO ₃ ) ₂ ] ₀ _. ₄ (KNO ₃ ) ₀ _. ₆

I.K. Moon, Y.H. Jeong

Thermochimica Acta > 2001 > 377 > 1-2 > 51-61

We investigated extensively equilibrium, nonequilibrium, and nonlinear aspects of the enthalpy relaxation in a supercooled liquid [Ca(NO ₃ ) ₂ ] ₀ _. ₄ (KNO ₃ ) ₀ _. ₆ . The equilibrium properties of relaxation, which are described in the framework of linear response theory, were determined from the frequency-dependent heat capacity measurements...

article

Application of an extended Tool-Narayanaswamy-Moynihan model - Part 1. Description of vitrification and complex heat capacity measured by temperature-modulated DSC

Stefan Weyer, Mikhail Merzlyakov, Christoph Schick

Thermochimica Acta > 2001 > 377 > 1-2 > 85-96

Complex heat capacity in equilibrium can be considered as a compliance in the scheme of linear response. Nevertheless, often the Tool-Narayanaswamy-Moynihan (TNM) or the Kovacs-Aklonis-Hutchinson-Ramos (KAHR) models are used to describe complex as well as total heat capacity in the glass transition region. This is attractive because the TNM-KAHR models take into account the dependence of the relaxation...

article

Author Index

Thermochimica Acta > 2001 > 377 > 1-2 > 211-212

article

Nucleotide-induced changes in muscle fibres studied by DSC and TMDSC

D. Lõrinczy, F. Könczöl, L. Farkas, J. Belagyi, more

Thermochimica Acta > 2001 > 377 > 1-2 > 205-210

Differential scanning calorimetry (DSC) was used in conventional and temperature-modulated mode to study the energetics of myosin in skeletal muscle fibres in different states of the actomyosin ATPase cycle. Psoas muscle fibres from rabbit were used in the experiments with and without the presence of nucleotides (ATP, ADP, AMP-PNP) and ATP or ADP+orthovanadate.In the complex DSC pattern, the higher...

article

Modern calorimetry: going beyond tradition

Yoon-Hee Jeong

Thermochimica Acta > 2001 > 377 > 1-2 > 1-7

Calorimetry has been a traditional tool for obtaining invaluable thermodynamic information of matter, the free energy. We describe recent efforts to go beyond this traditional calorimetry. After introducing dynamic heat capacity, we present the various experimental methods to measure it. Applications and future prospects are also given.

article

Volume Contents

Thermochimica Acta > 2001 > 377 > 1-2 > 217

article

Simultaneous measurements of complex heat capacity and complex thermal conductivity by two-channel AC calorimeter

A.A. Minakov, S.A. Adamovsky, C. Schick

Thermochimica Acta > 2001 > 377 > 1-2 > 173-182

The new capabilities of the advanced two-channel AC calorimetry, when working at frequencies above quasi-static limit, were shown. The idea of the method was to use the information about the phases and the amplitudes of the temperature oscillations on both sides of a plate-like sample for direct simultaneous determination of the complex heat capacity C(ω) and the complex thermal conductivity λ(ω),...

article

Simultaneous multi-frequency TMDSC measurements

M. Merzlyakov, C. Schick

Thermochimica Acta > 2001 > 377 > 1-2 > 193-204

We presented a study of advantages and limitations of different temperature-time profiles for simultaneous multi-frequency TMDSC measurements. Theoretical consideration was followed by some experimental examples. We showed that the optimal program temperature should contain sharp steps. In experiments higher harmonics of heat flow rate up to 100th were detected which means simultaneous covering two...

article

Frequency dependent heat capacity in the cure of epoxy resins

G. Van Assche, B. Van Mele, Y. Saruyama

Thermochimica Acta > 2001 > 377 > 1-2 > 125-130

Different temperature modulated differential scanning calorimetry (TMDSC) approaches were explored for studying the frequency dependence of the vitrification phenomenon during the cure of a thermosetting epoxy resin. All approaches show the expected decrease in vitrification time with increasing frequency. Light (heating) (temperature) modulated DSC (LMDSC), developed by Saruyama, offers the advantage...

article

Measurement of heat capacity to gain information about time scales of molecular motion from pico to megaseconds

B. Wunderlich, M. Pyda, J. Pak, R. Androsch

Thermochimica Acta > 2001 > 377 > 1-2 > 9-33

Molecular motion has primarily a time scale of picoseconds. Quantum mechanical models of small-amplitude vibrations and local, large-amplitude motions can be fitted quantitatively to equilibrium heat capacities. Macroscopic calorimetry, thus yields indirectly the characteristic frequencies of molecular motion in the range of 10 ¹ ¹ -10 ¹ ³ Hz. At lower temperature, much of...

article

Adiabatic calorimeter as an ultra-low frequency spectrometer: interplay between phase and glass transitions in solids

H. Suga

Thermochimica Acta > 2001 > 377 > 1-2 > 35-49

Principle and procedure of an adiabatic calorimeter used for an ultra-low frequency spectrometer was described in detail. Structural relaxation in glass-forming liquids and vapor-quenched non-crystalline solids were compared in terms of the Kohlrausch-Williams-Watts' (KWW) empirical equation and the fictive temperature. Kinetic parameters for the structural recovery were analyzed by using the Adam-Gibbs...

article

Subject Index

Thermochimica Acta > 2001 > 377 > 1-2 > 213-216

article

Glass transition cooperativity from heat capacity spectroscopy-temperature dependence and experimental uncertainties

H. Huth, M. Beiner, S. Weyer, M. Merzlyakov, more

Thermochimica Acta > 2001 > 377 > 1-2 > 113-124

The influence of experimental uncertainties of calorimetric parameters from heat capacity spectroscopy on the temperature-dependent glass transition cooperativity N _α from the fluctuation approach is studied. Glass transition parameters from 3ω method and temperature modulated DSC are compared. The influence of the stationary temperature field on the output of the 3ω method is studied. Special...

Volume:
377
Year:
2001

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1-2 (22)

Keywords

GLASS TRANSITION (5)
COMPLEX HEAT CAPACITY (3)
DYNAMIC HEAT CAPACITY (3)
HEAT CAPACITY (3)
AC CALORIMETRY (2)
DSC (2)
ENTHALPY RELAXATION (2)
POLYMERS (2)
TEMPERATURE-MODULATED CALORIMETRY (2)
THERMAL CONDUCTIVITY (2)
ADIABATIC CALORIMETRY (1)
CONFIGURATIONAL ENTROPY (1)
DIELECTRIC RELAXATION (1)
DYNAMIC CALORIMETRY (1)
ENTHALPY (1)
FLUCTUATION DISSIPATION THEOREM (1)
FREQUENCY (1)
GLASS TRANSITION REGION (1)
GLASSY CRYSTALS (1)
GLASSY LIQUIDS (1)
GLYCEROL (1)
HEAT CAPACITY SPECTRUM (1)
HIGHER HARMONICS (1)
KINETIC MODELS (1)
LATENT HEAT (1)
LIGHT HEATING MODULATED TEMPERATURE DSC (1)
LINEAR RESPONSE (1)
MELTING (1)
MODULATION CALORIMETRY (1)
NONLINEAR RELAXATION (1)
NUCLEOTIDES (1)
PHASE TRANSITIONS (1)
PHOTOPYROELECTRIC (PPE) (1)
PHOTOTHERMAL (1)
POLYETHYLENE CRYSTAL (1)
POLYMER MELTING (1)
POLYPROPYLENE GLYCOL (1)
POLYSTYRENE (PS) (1)
RELAXATION (1)
RELAXATION PROCESS (1)
REVERSIBILITY (1)
SKELETAL MUSCLE CONTRACTION (1)
SPECIFIC HEAT CAPACITY (1)
TEMPERATURE DEPENDENCE (1)
TEMPERATURE MODULATED DIFFERENTIAL SCANNING CALORIMETRY (1)
TEMPERATURE MODULATION CALORIMETRY (1)
TEMPERATURE-MODULATED DIFFERENTIAL SCANNING CALORIMETRY (1)
TEMPERATURE-MODULATED DSC (1)
TEMPERATURE-MODULATED DSC (TMDSC) (1)
THERMAL DIFFUSIVITY (1)
THERMAL EFFUSIVITY (1)
THERMAL WAVES (1)
THERMOPHYSICAL PROPERTIES (1)
THERMOSETTING POLYMER (1)
TIME DEPENDENCE (1)
TIME SCALE (1)
TMDSC (1)
TOOL-NARAYANASWAMY-MOYNIHAN MODEL (1)
ULTRA-HIGH MOLECULAR MASS POLYETHYLENE (1)
[PHYSICAL ASTRONOMY CLASSIFICATION SCHEME] 64.70.P (1)
[PHYSICAL ASTRONOMY CLASSIFICATION SCHEME] 66.10.C (1)
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Thermochimica Acta

Time dependence of the complex heat capacity at the melting temperature of polyethylene crystals

The application of temperature-modulated DSC to the glass transition region - II. Effect of a distribution of relaxation times

Preface

Temperature-modulated differential scanning calorimetric measurements on nascent ultra-high molecular mass polyethylene

A new light driven spectrometer for the determination of complex heat capacities and conductivities by combination of effusivity and diffusivity measurements

Development of the front-detection photopyroelectric (FPPE) configuration for thermophysical study of glass-forming liquids

Enthalpy and dielectric relaxation in the glass transition region of polypropylene glycol

Equilibrium, nonequilibrium, and nonlinear enthalpy relaxation in a supercooled ionic liquid [Ca(NO ₃ ) ₂ ] ₀ _. ₄ (KNO ₃ ) ₀ _. ₆

Application of an extended Tool-Narayanaswamy-Moynihan model - Part 1. Description of vitrification and complex heat capacity measured by temperature-modulated DSC

Author Index

Nucleotide-induced changes in muscle fibres studied by DSC and TMDSC

Modern calorimetry: going beyond tradition

Volume Contents

Simultaneous measurements of complex heat capacity and complex thermal conductivity by two-channel AC calorimeter

Simultaneous multi-frequency TMDSC measurements

Frequency dependent heat capacity in the cure of epoxy resins

Measurement of heat capacity to gain information about time scales of molecular motion from pico to megaseconds

Adiabatic calorimeter as an ultra-low frequency spectrometer: interplay between phase and glass transitions in solids

Subject Index

Glass transition cooperativity from heat capacity spectroscopy-temperature dependence and experimental uncertainties

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