Thermal analysis methods applications

Another thermal analysis method available for catalyst characterization is microcalorimetiy, which is based on the measurement of the heat generated or consumed when a gas adsorbs and reacts on the surface of a solid [66-68], This information can be used, for instance, to determine the relative stability among different phases of a solid [69], Microcalorimetiy is also applicable in the measurement of the strengths and distribution of acidic or basic sites as well as for the characterization of metal-based catalysts [66-68], For instance, Figure 1.10 presents microcalorimetry data for ammonia adsorption on H-ZSM-5 and H-mordenite zeolites [70], clearly illustrating the differences in both acid strength (indicated by the different initial adsorption heats) and total number of acidic sites (measured by the total ammonia uptake) between the two catalysts. 

Extraction and Thermal-Optical Carbon Analysis Methods Application to Diesel Vehicle Exhaust Aerosol, Environ. Sci. Tech-noi, 18, 231-234 (1984). 

Thermal analysis methods are widely used in all fields of pharmaceutics. They are unique for the characterization of single compounds. The information correlated with the thermodynamic phase diagrams is extremely helpful for rational preformulation and development of new delivery systems. Very rapid and requiring only very small samples of material, these methods are applicable in development and also in production for quality control. The combination with spectroscopic and crystallographic data will allow better insight in complex phase changes behavior. 

The use of thermal analysis techniques has increased rapidly in the past ten years and their field of application is widening continuously. This new book provides an overview of the principal thermal analysis methods and their application in major areas of importance, and will bring the reader up-to-date with the latest advances in the field. Special Publication No. 117 Hardcover viii+296 pages ISBN 0 85186 375 2... 

Bidstrup, W. Senturia, S. (1987) Society of Plastics Engineers ANTEC 87, pp. 1035-1038. Billingham, N.C., Bott, D.C. Manke, A. S. (1981) Application of thermal analysis methods to oxidation and stabilization of polymers, in Grassie, N. (Ed.) Developments in Polymer Degradation - 3, London Applied Science. 

Table 16.1 Some Applications of Thermal Analysis Methods...

Thermal analysis methods can be broadly defined as analytical techniques that study the behaviour of materials as a function of temperature [1]. These are rapidly expanding in both breadth (number of thermal analysis-associated techniques) and in depth (increased applications). Conventional thermal analysis techniques include DSC, DTA, TGA, thermomechanical analysis, and dynamic mechanical analysis (DMA). Thermal analysis of a material can be either destructive or non-destructive, but in almost all cases subtle and dramatic changes accompany the introduction of thermal energy. Thermal analysis can offer advantages over other analytical techniques including variability with respect to application of thermal energy (step-wise, cyclic, continuous, etc.), small sample size, the material can be in any solid form - gel, liquid, glass, solid, ease of variability and control of sample preparation, ease and variability of atmosphere, it is relatively rapid, and instrumentation is moderately priced. Most often, thermal analysis data are used in conjunction with results from other techniques. 

Apart from combined TA techniques (on-line or not) the actual trends in thermal analysis are the introduction of modulated and high-resolution techniques, hyphenated thermal analysis methods e.g. TG-FTIR, TG-MS, DSC-XRD, etc.), alternative heating modes, microthermal analysis methods, industrial standardisation and quality control. Modulation means a periodic perturbation of a temperature program. Temperature modulation finds application in DSC, TG, DETA, TMA and uTA. Temperature-modulated techniques, such as Modulated DSC (MDSC ) and Modulated TGA (MTGATM), broaden the insight into the material properties. The use of modulated temperature programs in thermal methods has been reviewed [37,37a]. 

In view of the restrictions in space, it is impractical to review the immense volume of literature that describes the application of thermal analysis methods to textile fibers, yams, and fabrics. The objective of this section is therefore to describe examples of thermal processes in textile materials that have been selected to illustrate the behavior observed in specific samples. Comparison with these examples may help to identify and interpret similar processes and understand the performance of other materials. 

Brown, R. A., and Cassel, B., High Alumina Cements Background and Application of Thermal Analysis Methods, Lab., 9 45-56 (1977)... 

Perkin-Elmer, Thermal Analysis Literature, TA Application Studies Bulletin TAAS-I9, Characterization of Thermosets TAAS-20, Polymer Testing by TMA TAAS-22, Characterization and Quality Control of Engineering Thermoplastics by Thermal Analysis TAAS-25, Applications of TA in the Electrical and Electronic Industries TAAS-26, Applications of TA in the Automotive Industries TAAS-29, Use of Thermal Analysis Method in Eoam Research and Development. ... 

An alternative method of studying the molecular motions of a polymeric chain is to measure the complex permitivity of the sample, mounted as dielectric of a capacitor and subjected to a sinusoidal voltage, which produces polarization of the sample macromolecules. The storage and loss factor of the complex permitivity are related to the dipolar orientations and the corresponding motional processes. The application of the dielectric thermal analysis (DETA) is obviously limited to macromolecules possessing heteroatomic dipoles but, on the other hand, it allows a range of frequency measurement much wider than DMTA and its theoretical foundations are better established. 

A typical method for thermal analysis is to solve the energy equation in hydrodynamic films and the heat conduction equation in solids, simultaneously, along with the other governing equations. To apply this method to mixed lubrication, however, one has to deal with several problems. In addition to the great computational work required, the discontinuity of the hydrodynamic films due to asperity contacts presents a major difficulty to the application. As an alternative, the method of moving point heat source integration has been introduced to conduct thermal analysis in mixed lubrication. 

Table 7.87 shows the main features of on-line micro LC-GC (see also Table 7.86). The technique allows the high sample capacity and wide flexibility of LC to be coupled with the high separation efficiency and the many selective detection techniques available in GC. Detection by MS somewhat improves the reliability of the analysis, but FID is certainly preferable for routine analysis whenever applicable. Some restrictions concern the type of GC columns and eluent choice, especially using LC columns of conventional dimensions. Most LC-GC methods are normal-phase methods. This is partly because organic solvents used as eluents in NPLC are compatible with GC, making coupling simpler. RPLC-GC coupling is demanding water is not a suitable solvent for GC, because it hydrolyses the siloxane bonds in GC columns. On-line RPLC-GC has not yet become routine. LC-GC technology is only applicable to compounds that can be analysed by GC, i.e. volatile, thermally stable solutes. LC-GC is appropriate for complex samples which are difficult or even impossible to analyse by a single chromatographic technique. Present LC-GC methods almost exclusively apply on-column, loop-type or vaporiser interfaces (PTV).

Haines, P. J. Thermal Methods of Analysis Principles, Applications and Problems, Blackie A P, 1995. 

---