Fundamental thermal analysis

C. B. Murphy, Analytical reviews 1972/Fundamentals Thermal analysis. Anal. Chem. 44(5), 513R-524R (1972). 

The requirement of dimensional consistency places a number of constraints on the form of the functional relation between variables in a problem and forms the basis of the technique of dimensional analysis which enables the variables in a problem to be grouped into the form of dimensionless groups. Since the dimensions of the physical quantities may be expressed in terms of a number of fundamentals, usually mass, length, and time, and sometimes temperature and thermal energy, the requirement of dimensional consistency must be satisfied in respect of each of the fundamentals. Dimensional analysis gives no information about the form of the functions, nor does it provide any means of evaluating numerical proportionality constants. 

Collectively, the thermal analysis techniques can be used to compare different batches of gunpowder and its constituents or to make more fundamental studies of, for example, the stability of the explosive under various physical or chemical conditions. 

Urszula Domahska has been professor. Faculty of Chemistry, Warsaw University of Technology since February 1995. She has been the Head of the Physical Chemistry Division since September 1991 and vice director of the Institute of Fundamental Chemistry (1988-1990). She had long-term scientific visits as visiting professor Laboratoire De Thermodynamique Ft D Analyse Chimique, University of Metz, France University of Turku, Finland Faculty of Science, Department of Chemistry, University of Natal, South Africa Department of Chemical Engineering, Louisiana State University, United States. Her interests have included such areas of physical chemistry as thermodynamics, especially thermodynamics of phase equilibria, VLE, LLE, SLE, high-pressure SLE, separation science, calorimetry, correlation and prediction of physical-chemical properties, and ionic liquids. She is a member of the Polish Chemical Society member of the Polish Association of Calorimetry and Thermal Analysis member of lUPAC Commission on Solubility member of International Association of Chemical Thermodynamics and scientific advisor at the Journal of Chemical Engineering Data. 

T. Hatakeyama and F. X. Quinn, Thermal Analysis Fundamentals and Applications to Polymer Science, Chap. 4, Wiley, New York, 1994. 

Hatakeyama, T. and FIX. Quinn Thermal Analysis. Fundamentals and Applications to Polymer Science, 2nd Edition, John Wiley, Sons, Inc., New York, NY, 1999. 

Most research papers concerned with pharmaceutical microcalorimetry can usually be found in the pharmaceutical journals International Journal of Pharmaceutics (Elsevier Science Publishers BV, Amsterdam) and Pharmaceutical Research (Plenum Publishing Corporation, New York) while more fundamental work will be found in Thermochimica Acta (Elsevier Science Publishers BV, Amsterdam). Excellent reviews of the field of thermal analysis have been published every two years in the fundamental reviews issue of Analytical Chemistry by the late D Dollimore, most recently in 1998 (43). 

Differential Thermal Analysis. V.I. Fundamental Aspects. Ed. Mackenzie R. C. London and New York Academic Press, 1970. 

Giron, D. (1997). Thermal analysis of drugs and drug products. In Encyclopedia of pharmaceutical technology, Vol. 15 Thermal analysis of drugs and drug products to unit processes in pharmacy fundamentals (ed. J. Swarbrick and J. C. Boylan), pp. 1-79. Marcel Dekker, New York. [242, 243, 250, 253]... 

Basic Mechanisms. Finally, further work is necessary on fundamental mechanisms of individual fire retardants. These mechanisms are a function of the particular chemicals involved and the environmental conditions of the fire exposure. There is a need to establish common methods and conditions for determining these mechanisms in order to compare different treatments. This would give us a better understanding of how these compounds work in action and would provide a more efficient approach for formulating fire-retardant systems than a trial and error approach. Correlations also need to be established between rapid precise thermal analysis methods and standard combustion tests. Retardant formulations could be evaluated initially on smaller (research and development size) samples. The more promising treatments could be tested for flame-spread index, heat release rate, and toxic smoke production. 

The measurement of temperature is one of the fundamental means of assessing the properties of a system, going back to the simple method of putting one s hand on or in a system such as a pool of water. It is useful to consider this apparently trivial example in more detail as many of the principles of thermal analysis may be understood in this way. In reality, what is being performed is a comparison of the hotness of the water to that of the body (or more specifically that of the skin). This leads to two of the underpinning concepts of thermal analysis. The first is that we make measurements of thermal... 

The field of thermal analysis is extremely wide due to versatility of the methods and hence there is a considerable body of literature available on the topic. The interested reader is referred to texts that outline the fundamentals of thermal methods in more detail (1-4) and also two books that deal specifically with thermal analysis of pharmaceutical systems (5 6). 

Using differential scanning calorimetry (DSC) (or, less directly, differential thermal analysis (DTA)) (see Section 2.8.5., above) it is possible to measure several of the thermodynamic properties of solids and of solid state reactions. The DSC response is directly proportional to the heat capacity, Cp, of the sample, so that by use of a calibrant it is possible to obtain values of this fundamental thermodynamic property, at a particular temperature, or as an average over a specified temperature range. Other thermodynamic properties are readily derived from such measurements ... 

Theory and kinetic analysis (38 entries). Many aspects of the theory of kinetic analysis were discussed (27 entries). Some papers were specifically concerned with discrimination of fit of data between alternative kinetic expressions or with constant reaction rate thermal analysis. Other articles (11 entries) were concerned with aspects of the fundamental theory of the subject and with the compensation effect. The content of papers concerned with kinetic analyses appeared to accept the common basis of the applicability of the rate equations listed in Table 3.3. 

The fundamental research work was subvided into 3 parts [ 6o ] - thermogravimetric analysis (TGA) and differential thermal analysis (PTA) of minute samples (5 50 mg) of the material to be studied. Both techniques yield information on the rate of thermal decomposition, the heat of reaction, the kinetic parameters of this process (pseudo-order and activation energy) and the amount of residue. The analysis of the evolving product has been monitored by means of gas chromatography. High temperature oxidation of the residue allows to compare the reactivity of the carbonized residue. ... 

Figure 10.3 DTA curve for a polymer sample under a constant heating rate. (Reproduced with permission from T. Hatakeyama and F.X. Quinn, Thermal Analysis Fundamentals and Applications to Polymer Science, 2nd ed., John Wiley Sons Ltd, Chichester. 1999 John Wiley Sons Ltd.)...

It is generally acknowledged that DSC is the pre-eminent thermal analysis technique and that it has progressively become the established technique for the study of the thermal behavior of polymeric materials. Conventional DSC correlates thermal power with heat capacity and the integral thereof to energy and entropy. Thus, DSC has been applied to determine heat capacities of a wide range of materials. Conventional DSC is able to determine heat capacity to an uncertainty of 1-2% tmDSC is able to measure this parameter to an uncertainty of less than 1% with reproducible reliability. It is the temperature modulation feature of tmDSC which has confirmed this technique as the most versatile and most reliable of the thermal analysis techniques. Its versatility is further qualified by its ability to characterize the thermal behavior of materials without the need to have a detailed knowledge of the fundamental theoretical principles which underscore the basis of the technique. 

Differenhal scanning calorimetry (DSC) conshtutes one of the most widely used techniques for the study of polymers, parhcularly those systems that crystallize. Although the term DSC is used in conjunchon with many different instruments, fundamentally, these can be divided into two categories heat flow instruments based upon differenhal thermal analysis (DTA) and those which are true power compensated instruments. 

R.M. Cotta, S. Kakag, M.D. Mikhailov, F.V. Castellos, and C.R. (Tardoso, Transient flow and thermal analysis in microfluidics, Microscale Heat Transfer-Fundamentals and Applications in Biological Systems and MEMS, edited by... 

The fundamental equations for differential thermal analysis have been derived in section 2 namely,... 

Erom the practical point of view, fundamental information on the processability of polymers is usually obtained through thermal analysis, which provides knowledge of the main polymer transitions (melting and glass-to-rubber transition to the crystalline and amorphous phases, respectively). In addition to the well-established calorimetric techniques, experimental methods capable of revealing the motional phenomena occurring in the solid state have attracted increasing attention. 

---