Table Of ContentDifferential Scanning Calorimetry
Springer-Verlag Berlin Heidelberg GmbH
w.
G. W. H. Hahne, Hemminger,
H.-J. Flammersheim
Differential Scanning
Calorimetry
An Introduction for Practitioners
With 136 Figures and 13 Tables
i
Springer
Dr. G. W. H. Hahne
U niversitat Ulm
Sektion Kalorimetrie
Albert-Einstein-Allee 11
D -89069 Ulm
Dr. W. Hemminger
Physikalisch-Technische Bundesanstalt
Bundesallee 100
D -38116 Braunschweig
Dr. H.-J. Flammersheim
Universitat Jena
Institut fiir Physikalische Chemie
LessingstraBe 10
D -07743 Jena
ISBN 978-3-662-03304-3 ISBN 978-3-662-03302-9 (eBook)
DOI 10 .1 007/978-3-662-03302-9
Library of Congress Cataloging-in-Publication Data
Htlhne. G. W. H. (Giinther. Walther. Heinrich)
Differential scanning calorimetry: an introduction for practitioners / G. W. H. Hohne.
W. Hemminger. H.-J. Flammersheim.
Includes bibliographical references and index.
1. Calorimetry. 1. Hemminger, W. II. Flammersheim, H.-J., III. Title.
QC291.H64 1995 95-20483
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© Springer-Verlag Berlin Heidelberg 1996
Originally published by Springer-Verlag Berlin Heidelberg New York in 1996.
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Preface
Differential Scanning Calorimetry (DSC) is a well established measuring method
which is used on a large scale in different areas of research, development, and
quality inspection and testing. Over a large temperature range, thermal effects can
be quickly identified and the relevant temperature and the characteristic caloric
values determined using substance quantities in the mg range. Measurement values
obtained by DSC allow heat capacity, heat of transition, kinetic data, purity and
glass transition to be determined. DSC curves serve to identify substances, to set up
phase diagrams and to determine degrees of crystallinity.
This book provides, for the first time, an overall description of the most impor
tant applications of Differential Scanning Calorimetry. Prerequisites for reliable
measurement results, optimum evaluation of the measurement curves and esti
mation of the uncertainties of measurement are, however, the knowledge of the
theoretical bases of DSC, a precise calibration of the calorimeter and the correct
analysis of the measurement curve.
The largest part of this book deals with these basic aspects: The theory of DSC
is discussed for both heat flux and power compensated instruments; temperature
calibration and caloric calibration are described on the basis of thermodynamic
principles. Desmearing of the measurement curve in different ways is presented as
a method for evaluating the curves of fast transitions.
The instrumental data which are most important for the characterization of Dif
ferential Scanning Calorimeters are defined, and it is explained how they are
determined experimentally. This enables every potential buyer to ask the man
ufacturer for measured characteristic data which will allow him to compare the dif
ferent instruments available.
We are indebted to S.M. Sarge for a critical examination of the manuscript
and valuable suggestions for improvement and especially to M. J. Richardson for
helping us with the translation.
G. W. H. Hahne
w.
Hemminger
H.-J Flammersheim
Contents
1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 Types of Differential Scanning Calorimeters 7
2.1 The Heat Flux DSC . . . . . . . . . . . . . . . 8
2.1.1 Heat Flux DSC with a Disk-Type Measuring System 8
2.1.2 Heat Flux DSC with a Cylinder-Type Measuring System 11
2.2 The Power Compensation DSC . . . . . . . . . . . . . . 14
3 Theoretical Fundamentals of Differential Scanning
Calorimeters . . . 21
3.1 The Heat Flux DSC 21
3.2 The Power Compensation DSC 38
4 Calibration of Differential Scanning Calorimeters 41
4.1 Aspects of Quality Assurance 41
4.2 Thermodynamic Aspects 42
4.3 Temperature Calibration 43
4.3.1 Calibration Procedure . . 45
4.3.2 Arguments in Support of the Temperature Calibration Procedure 52
4.3.3 Examples of Temperature Calibration 54
4.4 Caloric Calibration .... 61
4.4.1 Heat Flow Rate Calibration . . . 62
4.4.2 Peak Area Calibration . . . . . . 65
4.4.3 Examples of Caloric Calibrations 68
4.5 Conclusions Regarding the Calibration of DSCs 72
4.6 Calibration Substances ............ . 73
4.6.1 Calibration Substances for Temperature Calibration 74
4~6.2 Calibration Substances for Heat Flow Rate Calibration 75
4.6.3 Calibration Substances for Peak Area Calibration ... 76
VIII Contents
5 The DSC Curve 81
5.1 Characteristic Tenns 82
5.2 Influencing Parameters .. . . . . . . . . . . . . . . . . . 83
5.3 The Baseline and the Detennination of the Thennodynamic
Functions ......................... . 84
5.4 Desmearing ofthe DSC Curve . . . . . . . . . . . . . . . 89
5.4.1 Correction of the Temperature and Heat Flow Rate Indicated 91
5.4.2 Subtraction of the Baseline ........... . 92
5.4.3 Calculation of the True Flow Rate into the Sample 92
5.4.4 Advanced Desmearing 96
5.4.5 Further Calculations 102
5.5 Interpretation and Presentation 103
6 Applications of Differential Scanning Calorimetry . . . . . . . 105
6.1 General Applications Without Sophisticated Evaluation
of the Measured Curve ............. . 105
6.1.1 Identification of Substances, the Phase Behavior 105
6.1.2 Detennination of Phase Diagrams ....... . 111
6.1.3 Safety Aspects ................. . 113
6.1.4 Characterization of Polymers by Thennal Analysis;
Effects of Origin and Thennal History . . . . . . . . . . . . . 114
6.1.5 Detennination of the Degree of Crystallinity . . . . . . . . . . 115
6.2 Applications Requiring a Detailed Evaluation ofthe Measured
Curve ................ . 118
6.2.1 Measurements ofthe Heat Capacity 118
6.2.1.1 The "Classical" Three Step Procedure 119
6.2.1.2 The "Absolute" Dual Step Method .. 124
6.2.1.3 A Variation of the Classical Technique 124
6.2.1.4 A Discontinuous Procedure . . . . . . 127
6.2.1.5 Detennination Using the Dual DSC 129
6.2.1.6 General Precautions for the Minimization of Erors 129
6.2.1.7 Typical Applications of Heat Capacity Measurements 130
6.2.1.8 Heat Capacity Measurements with Temperature Modulated DSC 132
6.2.2 The Investigation of Reactions .. 132
6.2.2.1 Detennination of Heats of rEaction 133
6.2.2.2 Kinetic Investigations ...... . 139
6.2.2.2.1 Introduction and Definitions .. . 139
6.2.2.2.2 Experimental Preconditions for a Reliable Kinetic Analysis 141
6.2.2.2.3 Isothennal or Non-isothennal Reaction Mode? ..... . 143
6.2.2.2.4 Thennal Activation of the Sample or Activation by High Energy
Radiation ............................ . 146
6.2.2.2.5 Remarks on the Influence of Different Phases ......... . 149
6.2.2.2.6 Evaluation of Overall Rate Laws and Fonnal Kinetic Parameters 149
Contents IX
6.2.2.2.7 Determination of the True Reaction Mechanism 152
6.2.2.2.8 Selected Examples ............. 153
6.2.3 The Glass Transition Process . . . . . . . . . . 160
6.2.3.1 The Phenomenology of the Glass Transition . . 160
6.2.3.2 The Nature ofthe Glass Transition and Consequences
for DSC-Measurements . . . . . . . . . . . . . . . . 161
6.2.3.3 Definition and Determination of the Glass Transition
Temperature 1'g .................... 163
6.2.3.3.1 Conventional Glass Transition Temperatures . . . . . 163
6.2.3.3.2 The Thermodynamically Defined Glass Transition Temperature 165
6.2.3.4 Applications of Glass Transition Measurements ........ 171
7 Evaluation of the Performance of a Differential Scanning
Calorimeter ................ . 181
7.1 Characterization of the Complete Instrument 181
7.2 Characterization of the Measuring System .. 181
7.3 Characterization of the Results of a Measurement 186
7.4 Check List for DSCs 188
Appendix 1 189
Appendix 2 193
References 211
Subject Index 217
List of Symbols
A area, pre-exponential factor
C heat capacity, electric capacity
E energy
H enthalpy
K factor (calibration), coefficient
L thermal conductance
P electric power
Q heat
R resistance (thermal, electric), gas constant
S entropy
T temperature
U internal energy, voltage
V volume
W work, electric energy
a coefficient, apparatus function
c specific heat capacity
d distance
electric current
k proportionality factor, calibration factor, rate constant
I length, distance
m mass
n reaction order
p pressure
r rate of reaction
t time
w weight fraction
x mole fraction
a degree of reaction
f3 heating rate
r expansivity coefficient
E emissivity
A. thermal conductivity
v stoichiometric number
CP heat flow rate
p density
standard deviation
(1
'f time constant
X compressibility
~ extent of reaction, composition, conversion
