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Temperature-modulated differential scanning calorimetry (TMDSC) generated with a centrosymmetric saw-tooth oscillation can be considered to be a sinusoidal modulation with multiple frequencies. Different harmonics of the Fourier series of the heat-flow rate and heating rate of a single sawtooth-modulation can be deconvoluted to extract data pertaining to different frequencies. In order to give the higher harmonics similar amplitudes, a complex, but simple-to-program, sawtooth-modulation is generated for the harmonics 1,3,5,7 and 9. In this fashion a single experiment can produce a frequency-dependent analysis under identical thermal history. Application of this method to TMDSC includes the calibration for heat capacity determination of high precision, even if steady state and a negligible temperature gradient are not achieved. The measurement of the frequency (?) dependence of the heat-flow rate (AHF) and sample temperature (ATs) allows to evaluate the expression: CP=AHF/(ATs??)[1+(???)2]0.5 where the relaxation time ? is to be determined empirically from the multiple data generated by the single run. Typical values for the relaxation time for commercial calorimeters are between 3 and 9 s rad-1. Frequency-dependent, apparent reversing heat capacities in the glass transition region and within first-order transition regions may also be analyzed to study local equilibria in globally metastable polymeric solids.
The special technical publication has been compiled from the 15 presentations at a May 2000 Association symposium in Toronto. They cover the fundamentals of the techniques, its use in curing and chemical reactions, measuring the glass transition and melting by modulated and comparative techniques, g
MTDSC provides a step-change increase in the power of calorimetry to characterize virtually all polymer systems including curing systems, blends and semicrystalline polymers. It enables hidden transitions to be revealed, miscibility to be accurately assessed, and phases and interfaces in complex blends to be quantified. It also enables crystallinity in complex systems to be measured and provides new insights into melting behaviour. All of this is achieved by a simple modification of conventional DSC. In 1992 a new calorimetric technique was introduced that superimposed a small modulation on top of the conventional linear temperature program typically used in differential scanning calorimetry. This was combined with a method of data analysis that enabled the sample’s response to the linear component of the temperature program to be separated from its response to the periodic component. In this way, for the first time, a signal equivalent to that of conventional DSC was obtained simultaneously with a measure of the sample’s heat capacity from the modulation. The new information this provided sparked a revolution in scanning calorimetry by enabling new insights to be gained into almost all aspects of polymer characteristics. This book provides both a basic and advanced treatment of the theory of the technique followed by a detailed exposition of its application to reacting systems, blends and semicrystalline polymers by the leaders in all of these fields. It is an essential text for anybody interested in calorimetry or polymer characterization, especially if they have found that conventional DSC cannot help them with their problems.
Thermal analysis is an old technique. It has been neglected to some degree because developments of convenient methods of measurement have been slow and teaching of the understanding of the basics of thermal analysis is often wanting. Flexible, linear macromolecules, also not as accurately simply called polymers, make up the final, third, class of molecules which only was identified in 1920. Polymers have neverbeenfullyintegratedintothedisciplinesofscienceandengineering. Thisbook is designed to teach thermal analysis and the understanding of all materials, flexible macromolecules, as well as those of the small molecules and rigid macromolecules. The macroscopic tool of inquiry is thermal analysis, and the results are linked to microscopic molecular structure and motion. Measurements of heat and mass are the two roots of quantitative science. The macroscopic heat is connected to the microscopic atomic motion, while the macroscopic mass is linked to the microscopic atomic structure. The macroscopic unitsofmeasurementofheatandmassarethejouleandthegram,chosentobeeasily discernable by the human senses. The microscopic units of motion and structure are 12 10 the picosecond (10 seconds) and the ångstrom (10 meters), chosen to fit the atomic scales. One notes a factor of 10,000 between the two atomic units when expressed in “human” units, second and gram—with one gram being equal to one cubic centimeter when considering water. Perhaps this is the reason for the much better understanding and greater interest in the structure of materials, being closer to human experience when compared to molecular motion.
Presents a solid introduction to thermal analysis, methods, instrumentation, calibration, and application along with the necessary theoretical background. Useful to chemists, physicists, materials scientists, and engineers who are new to thermal analysis techniques, and to existing users of thermal analysis who wish expand their experience to new techniques and applications Topics covered include Differential Scanning Calorimetry and Differential Thermal Analysis (DSC/DTA), Thermogravimetry, Thermomechanical Analysis and Dilatometry, Dynamic Mechanical Analysis, Micro-Thermal Analysis, Hot Stage Microscopy, and Instrumentation. Written by experts in the various areas of thermal analysis Relevant and detailed experiments and examples follow each chapter.
An all-in-one reference work covering the essential principles and techniques on thermal behavior and response of polymeric materials This book delivers a detailed understanding of the thermal behavior of polymeric materials evaluated by thermal analysis methods. It covers the most widely applied principles which are used in method development to substantiate what happens upon heating of polymers. It also reviews the key application areas of polymers in materials science. Edited by two experts in the field, the book covers a wide range of specific topics within the aforementioned categories of discussion, such as: Crucial thermal phenomena - glass transition, crystallization behavior and curing kinetics Polymeric materials that have gained considerable interest over the last decade The latest advancements in techniques related to the field, such as modulated temperature DSC and fast scanning calorimetry The recent advances in hyphenated techniques and their applications Polymer chemists, chemical engineers, materials scientists, and process engineers can use this comprehensive reference work to gain clarity on the topics discussed within and learn how to harness them in practical applications across a wide range of disciplines.
The authors show how DSC can be applied to various fields of polymers science where other methods have been unsuccessful. They discuss the ways in which DSC facilitates quantitative studies of the thermodynamic parameters and kinetics of melting, crystallization, liquid-crystallization, and different phase and relaxation transitions.
The monograph presents the various methods of the modulation and of measuring the temperature oscillations. Important applications of the modulation techniques for studying physical phenomena in solids and liquids are considered in depth (equilibrium point defects, phase transitions, superconductors, liquid crystals, biological materials, relaxation phenomena in specific heat, etc).