Rückblick GEFTA Jahrestagung 1999

Monitoring of thermal decomposition processes with TGA/SDTA/FTIR

Frank Hoffmann
Mettler-Toledo GmbH, Gießen



The current frontier in thermal analysis methods lies in the application of combined techniques. Chemical analysis of volatile components produced during a TG experiment increases the usefulness of mass loss data. Additional information on thermal effects can be received by means of simultaneous DTA measurements. Like a puzzle, summarized results will lead to information about the reaction dynamic of thermal decomposition process, too.

The coupling system TGA/SDTA 851e (METTLER TOLEDO) and Protege 460 (Nicolet Instrument) provides a optimized interface between the two instruments. It allows the assignment of evolved components to decomposition steps detected by TG within one experiment. Evolved gas atmosphere can be analyzed and identified into single components by computer-assisted analysis. Calibration of the SDTA signal with a cp-standard material like sapphire or a heat of fusion standard like indium in a second run will result quantitative information on heat of reaction and transition.

For measurements on novel flooring materials regarding fireproof behavior, a sample of vinyl flooring was investigated by means of simultaneous TGA/SDTA/FTIR experiments. Investigations covered a range up to 823 K. The SDTA-signal was calibrated with a sapphire reference for quantitative results on heat of reaction. Within the range of 4000 cm-1 to 400 cm-1 the FTIR-data were collected while heating up the sample.

The results will be discussed regarding thermal stability, heats of reaction and dynamic of the decomposition process. The separation of overlapping effects while heating up the sample will be shown. Finally, the discussion will lead to a characterization of the decomposition mechanism.

Furthermore, the efficiency of the coupling system will be shown on the characterization of elastomers, used in automotive industry related to quality control. Online TG/FTIR results on thermal decomposition of 2 different materials covering a range up to 1173 K will be presented and discussed with regard to analysis of additives, desorption behavior and competitive analysis.

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