Degradation thermal analysis techniques

A comprehensive review of compositional and failure analysis of polymers, which includes many further examples of analysis of contaminants, inclusions, chemical attack, degradation, etc., was published in 2000 [2], It includes details on methodologies, sampling, and sample preparation, and microscopy, infrared spectroscopy, and thermal analysis techniques. 

While physicochemical and spectroscopic techniques elucidate valuable physical and structural information, thermal analysis techniques offer an additional approach to characterize NOM with respect to thermal stability, thermal transitions, and even interactions with solvents. Information such as thermal degradation temperature (or peak temperature), glass transition temperature, heat capacity, thermal expansion coefficient, and enthalpy can be readily obtained from thermal analysis these properties, when correlated with structural information, may serve to provide additional insights into NOM s environmental reactivity. 

Whereas Redfern [57] has pointed out the advantages of simultaneous thermal analysis techniques (particularly TG-DSC and TG-DTA) over techniques conducted singly, an even more complete thermal profile is provided when a thermal analyser is coupled to some form of gas analyser (MS or FTIR). Mohler and co-workers [51] have reported TG-DSC-MS of the thermal decomposition of the vulcanisation accelerator tetramethyl thiuram disulphide (TMTD) in rubber degradation of TMTD starts at about 155 °C, as evidenced by m/z 76 (CS2) and 44 (radical of the secondary dimethylamine). 

Many advances have been made in development of P-DSC and other thermal analysis techniques in the study of oxidation reactions in fatty derivatives such as biodiesel. Kinetic parameters and phase transitions associated with oxidative degradation may be rapidly and accurately determined. However, the applicability of P-DSC may be limited in analysis of fuel formu-... 

DSC is a thermal analysis technique that is used to measure the temperatures and energy flows related to transitions in materials as a function of time and temperature.These measurements provide qualitative and quantitative information about physical and chemical changes that involve endothermic or exothermic processes or changes in heat capacity. Any event, such as loss of solvent, phase transitions, crystallization temperature, melting point, and degradation temperature of the plastic sample, result in a change in the temperature of the sample. The systems available cover a wide temperature range, e g., -60°Cto>l,500°C. 

Abou El Naga, H. H. et al Testing Thermooxidation Stability for Industrial Oil via Thermal Analysis Techniques. 6. Int. Kolloquium. Technische Akademie Esslingen, Jan. 1988. [4-27] Zeman, A. et al. The DSC Cell - A Versatile Tool to Study Thermal-Oxidative Degradation of Lubricants and Related Problems. Thermochimica Acta 80 (1984) p. 1-9. 

Thermal properties Thermal properties are the properties of materials that change with temperature. They are studied by thermal analysis techniques, which include DSC, thermogravimetric analysis (TGA), differential thermal analysis (DTA), thermomechanical analysis (TMA), dynamic mechanical analysis (DMA)/dynamic mechanical thermal analysis (DMTA), dielectric thermal analysis, etc. As is well known, TGA/DTA and DSC are the two most widely used methods to determine the thermal properties of polymer nanocomposites. TGA can demonstrate the thermal stability, the onset of degradation, and the percentage of silica incorporated in the polymer matrix. DSC can be... 

Dobkowski, Z. Thermal analysis techniques for characterization of polymer materials. Polymer Degradation and Stability, 2006, 91(3), 488 93. 

Thermal analysis techniques are used to study the properties of polymers, blends and composites and to determine the kinetic parameters of their stability and degradation processes.Here the property of a sample is continuously measured as the sample is programmed through a predetermined temperature profile. Among the most common techniques are thermogravimetry (TG) and differential scanning calorimetry (DSC). Dynamic mechanical analysis (DMA) and dielectric spectroscopy are essentially extensions of thermal analysis that can reveal more subtle transitions with temperature as they affect the complex modulus or the dielectric function of the material. 

Thermogravimetric analysis (TGA) is the most widely used thermal analysis technique, although other techniques such as differential scanning calorimetry (DSC) and differential thermal analysis (DTA) have also been used for polymer blends (see Table 8.1). In this section, we will limit our discussion to TGA, as its results (such as onset degradation temperature, degradation rate, and kinetic parameters) are most indicative of the fire performance of materials in fires. 

Table 5.1 Thermal analysis techniques and the principal parameters used to study the effects of (bio)degradation on the physical and chemical properties of polymers. 

Many physical and chemical processes are involved in the degradation of sealants and adhesives. Thermal analysis techniques have been used to characterize polymeric adhesives and sealant formulations and also to study the proeesses of degradation when they are exposed to natural elements. The applieation of techniques such as TG, DSC, DTG, Dynamic Mechanical Analysis, Dynamic Mechanical Thermal Analysis, Thermomechanical Analysis, and Dynamic Load Thermomechanical Analysis for such materials has been discussed in Ch. 14. 

Polymer and Other Degradation Studies Using Thermal Analysis Techniques... 

In Py-GC/MS the ability to analyze such small quantities of material, importantly allows degradation and off-gassing processes to be studied in a non-diffusion-limited regime. This feature is in contrcist to the limitations of bulk thermal analysis techniques. The Py-GC/MS is typically employed in a rapid bcdhstic mode (40-1200°C, 500-1000°C/min) providing hi-fidehty, in-depth chemiccil speciation data from the degradation of complex orgcuiic materials such as silicones. 

This final degradative step in the thermal analysis can, of course, be replaced by some other analytical technique. Of course, water and possibly other volatile additives may have been lost. A novel approach which has been suggested involves trapping temperature fractions (e.g., 100-300 300-400 etc.) from the heated effluent of a TGS-1 (or possibly of a modified DSC-2), on a substrate such as a charcoal or silica gel filter, removal by heat or solvent and running gas chromatography on the degradation products. 

Thermal analysis is a group of techniques in which a physical property of a substance is measured as a function of temperature when the sample is subjected to a controlled temperature program. Single techniques, such as thermogravimetry (TG), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), dielectric thermal analysis, etc., provide important information on the thermal behaviour of materials. However, for polymer characterisation, for instance in case of degradation, further analysis is required, particularly because all of the techniques listed above mainly describe materials only from a physical point of view. A hyphenated thermal analyser is a powerful tool to yield the much-needed additional chemical information. In this paper we will concentrate on simultaneous thermogravimetric techniques. 

Thermogravimetry is a technique that measures the weight change of a sample as a function of temperature or time (time is suitable only when thermal analysis is performed at specified constant temperature increments). The solid or liquid sample is heated or cooled at a selected rate or isothermally maintained at a fixed temperature. TG is used to measure degradation, oxidation, reduction, evaporation, sublimation, and other heat-related changes occurring in polymers. 

Thermal analysis is capable of providing accurate information on the phase transition temperatures, degradation temperatures, heat capacity, and enthalpy of transition of polymers using comparatively simple DTA, DSC, and TG instruments. The measurement time is short compared with other techniques, such as viscoelastic measurement and nuclear magnetic resonance spectroscopy. Moreover, any kind of material, e.g., powders, flakes, films, fibers, and liquids, may be used. The required amount of sample is small, normally in the range of several milligrams. 

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