Thermoanalytical techniques

Thermal analysis helps in measuring the various physical properties of the polymers. In this technique, a polymer sample is subjected to a controlled temperature program in a specific atmosphere and properties are measured as a function of temperature. The controlled temperature program may involve either isothermal or linear rise or fall of temperature. The most common thermoanalytical techniques are (1) differential scanning analysis (DSC), (2) thermomechanical analysis (TMA), and (3) thermogravimetry (TG). 

Thermoanalytical techniques such as differential scanning calorimetry (DSC) and thermogravi-metric analysis (TGA) have also been widely used to study rubber oxidation [24—27]. The oxidative stability of mbbers and the effectiveness of various antioxidants can be evaluated with DSC based on the heat change (oxidation exotherm) during oxidation, the activation energy of oxidation, the isothermal induction time, the onset temperamre of oxidation, and the oxidation peak temperature. 

First-order phase transitions can be detected by various thermoanalytical techniques, such as DSC, thermogravimetric analysis (TGA), and thermomechanical analysis (TMA) [31]. Phase transitions leading to visual changes can be detected by optical methods such as microscopy [3], Solid-solid transitions involving a change in the crystal structure can be detected by X-ray diffraction [32] or infrared spectroscopy [33], A combination of these techniques is usually employed to study the phase transitions in organic solids such as drugs. 

On the basis of this study of the preignition, ignition combustion reactions of Black Powder by thermoanalytical techniques, Campbell and Weingarten (Ref 1) proposed that the preignition reaction (1) is between S KN03, which is sufficiently exothermal to activate the propagative combustion reaction between charcoal ... 

An overview of the analytical techniques most frequently used that provide molecular and crystalline structure is illustrated in Scheme 1.8. Basically, they can be grouped into histochemical and immunological methods, diffraction, spectroscopic, spectrometric, chromatographic, and thermoanalytical techniques. 

Table 3.5 Various thermoanalytical techniques for thermal analysis.

Bart and co-workers [25] and others [34, 101, 163] have reviewed the application of TG-MS for the study of polymeric materials, thermoplastics, thermosets and elastomers. This thermoanalytical technique is used for the structural characterisation of homopolymers, copolymers, polymeric blends and composites and finds application in the detection of monomeric residuals, solvents, additives, (toxic) degradation products, etc. Information is... 

H2) Freeman, S., and B. Carroll The application of Thermoanalytical techniques to reaction kinetics. The Thermogravimetric Evaluation of the Kinetics of the Decomposition of Calcium Oxalate Monohydrate. J. Phys. Chem. 62, 394/ 397 (1958). 

Giron, D. (2001), Investigations of polymorphism and pseudopolymorphism in pharmaceuticals by combined thermoanalytical techniques, J. Thermal Anal. Calor., 64, 37-... 

If a physical property of a sample is measured during heating as a function of temperature, the technique is commonly named a thermoanalytical technique. 

Analytical pyrolysis is considered somehow apart from the other thermoanalytical techniques such as thermometry, calorimetry, thermogravimetry, differential thermal analysis, etc. In contrast to analytical pyrolysis, thermoanalytical techniques are not usually concerned with the chemical nature of the reaction products during heating. Certainly, some overlap exists between analytical pyrolysis and other thermoanalytical techniques. The study of the kinetics of the pyrolysis process, for example, was found to provide useful information about the samples and it is part of a series of pyrolytic studies (e.g. [6-8]). Also, during thermoanalytical measurements, analysis of the decomposition products can be done. This does not transform that particular thermoanalysis into analytical pyrolysis (e.g. [9]). A typical example is the analysis of the gases evolved during a chemical reaction as a function of temperature, known as EGA (evolved gas analysis). 

These examples are sufficient to clearly reveal the pre-eminence of DSC as the thermoanalytical technique of choice in materials science. 

Solid compounds, solid solutions, and solid mixtures can be differentiated through X-ray diffraction powder analysis and DSC, or other thermoanalytical techniques as mentioned in Sections 2,4.2 and 2.5.2. 

Microthermal analysis is a recently introduced thermoanalytical technique that combines the principles of scanning probe microscopy with thermal analysis via replacement of the probe tip with a thermistor. This allows samples to be spatially scanned in terms of both topography and thermal conductivity, whereby placing the probe on a specific region of a sample and heating, it is possible to perform localized thermal analysis experiments on those regions. 

Nebuloni M. [Thermoanalytic techniques for the study of pharmaceutical products]. Boll Chim Parm 1990 Mar 129(3) 87-96. Italian. 

Thermoptometry is defined as a family of thermoanalytical techniques in which an optical property of the sample is monitored against time or temperature, while the temperature of the sample, in a specified atmosphere, is programmed. Two established examples are thermomicroscopy (observation under a microscope) and thermoluminescence (1). Thermomicroscopy is also referred to as thermal microscopy, optical thermal analysis, hot-stage microscopy (HSM), or fusion methods. 

Mike Reading, Ph.D., is internationally recognized for his work on the development of novel thermoanalytical techniques. After receiving a B.Sc. and Ph.D. at Salford University and doing postdoctoral work in France (the CNRS center for calorimetry and thermodynamics, Marseilles), he worked with ICI until 1997. He left to join the IPTME at Loughborough University where he was director of the Advanced Thermal Methods Group. In 2004 he moved to the University of East Anglia to take up a chair in pharmaceutical characterization science. 

Th e thermoanalytical techniques have been used with great success in the field of synthetic fibers, and have been applied to studies of cellulose. For the latter, pyrolysis Avas found to be best conducted in a nitrogen atmosphere, to avoid the poor curves caused by overlapping reactions that occur in an oxidizing atmosphere. The effect of various potential fire-retardants on the thermal degradation of cellulose has also been studied successfully in this way. However, in the starch field, unfortunately, these valuable techniques have not yet been applied with sufficient care and attention paid to those complicating factors already outlined. 

In addition to the above IPGCS system, other thermoanalytical techniques were used also in this work. This includes a conventional pyrolysis-GC-mass spectrometry system which consists of a CDS Pyro-probe 100, a Perkin-Elmer 990 GC, and a Hitachi-Perkin-Elmer RMV 66 mass spectrometer, as well as a duPont 900 thermal analyzer. 

DSC, and dynamical mechanical thermal analysis (DMTA) have emerged as powerful thermoanalytical techniques to monitor physical and chemical changes in both natural and synthetic polymers. 

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