The use of reduced pressure to expand the capabilities of TGA–FTIR

The benefits of coupling a Fourier transform infrared (FTIR) spectrometer to a thermogravimetric analyzer (TGA) are well known. FTIR spectroscopy provides information about the evolved gases that can lead to a better understanding of the thermal behavior of the sample. The combination of the two techniques can give both qualitative and quantitative information about thermal decomposition and reaction mechanisms. One of the current limitations of TGA–FTIR is the temperature of the transfer line and the gas cell in the infrared spectrometer. The temperature of the interface to the FTIR cannot be as high as the temperature that can be achieved in the furnace, and this leads to possible trapping of high boiling compounds that are evolved from the sample. In this paper, a system is described for performing TGA–FTIR measurements at reduced pressures, which significantly improves the gas flow characteristics of the system for high boiling compounds. It is shown that reduced pressure also minimizes sample carryover, and reduces or eliminates trapping of material in the transfer line. Data are also presented that show that using the pressure as an experimental parameter can yield additional information about the structure of a sample, and about the thermal decomposition process.