Source thermogravimetric analysis

Chemical reactivity test data produced by employers or obtained from other sources (e.g., differential scanning calorimetry, thermogravimetric analysis, accelerating rate calorimetry). 

A thermocouple. Interfaced with the Hewlett-Packard 2116C computer, was employed to sense the temperature during the course of the thermogravimetric analysis. This probe was attached to the TG in order to monitor the actual temperature of the sample during each run. During sample analysis, the TG-jet separator connection was wrapped with heating tape and maintained at a temperature of 125 C while the jet separator oven was maintained at 135 C. The MS-jet separator transfer line was also wrapped with heat tape and maintained at 165 C while the source temperature was held at 230 C. 

Figure 2.5 Thermogravimetric analysis of solvent-cast a-chitin films. Wet chitin (solid line), dry chitin first scan (dashed line), and dry annealed chitin second scan (dash-dotted line) from 20 to 250 °C. Note that above 210 °C a-chitin thermally decomposes. A construction of tangent lines is operationally used to determine the onset of degradation (circa >210 °C). Source Reproduced with permission from Gonzalez-Campos JB, Prokhorov E, Luna-Barcenas G, Mendoza-Galvan A, Sanchez IC, Nuno-Donlucas SM, Garcia-Gaitan B, Kovalenko Y. J Polym Sci B Polym Phys 2009 47 932 [5]. Copyright 2009 John Wiley and Sons, Inc.

While the properties just described are utilized in specific kinds of experiments, the two most common properties studied as temperature is increased are mass and enthalpy. The change in mass as the temperature increases is produced by the loss of volatile products. Therefore, this technique is referred to as thermogravimetric analysis (TGA). Although the design of instruments will not be reviewed here, the basic components are a sensitive microbalance and a heat source that surrounds the sample and allows it to be heated at the desired rate. 

Figure 1.13 Thermogravimetric analysis of interlayers and composites. Source ...

The technique can also be used for studying the kinetics of chemical reactions, e.g., oxidation and decomposition. The conversion of a measured heat of fusion can be converted to a % crystallinity provided, of course, the heat of fusion for the 100% crystalline polymer is known. An example of a thermogram is shown in Figure 1. Refer to Thermal Analysis and Thermogravimetric Analysis. (Source Cheremisinoff, N.P. Polymer Characterization Laboratory Techniques and Analysis Noyes Publishers, New Jersey, 1996). 

The gases evolved during thermogravimetric analysis may be analyzed by mass spectrometry. A typical installation consists of a quadrupole mass spectrometer, fitted with an enclosed ion source, and sampling the effluent from a thermal analyzer via a heated capillary inlet with by-pass. 

Mansaray KG, Ghaly AE (1998) Thermogravimetric analysis of rice husk in an air atmosphere. Energy Sources 20 653-663... 

The nature of this source of waste plasterboard means that some degree of impurities and contaminants is inevitable. Thermogravimetric analysis (TGA) of materials was carried out using a PerkinElmer Pyris 1 theniiogravimetric analyser. The thermograph (Figure 3) confiims the presence of impurities in the PG. The loss of mass at >200° C implies the presence of a number of impurities and contaminants in the gypsum. 

Figure 12.1 Rheological changes in epoxy-amine resin during cure (a) thermogravimetric analysis, and (b) transitions as defined by e" curves. Source ...

Figure 2.2 Thermogravimetric analysis curves for polyethylenes in a nitrogen atmosphere ( ) purified polyethylene and (O) unpurified polyethylene. Source Author s own files...

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