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

The benefits of coupling a Fourier transform infrared (FTIR) spectrometer t o a thermogravimetric analyzer (TGA) are well known. FTIR spectroscopy prov ides information about the evolved gases that can lead to a better understa nding of the thermal behavior of the sample. The combination of the two tec hniques can give both qualitative and quantitative information about therma l decomposition and reaction mechanisms. One of the current limitations of TGA-FTIR is the temperature of the transf er line and the gas cell in the infrared spectrometer. The temperature of t he interface to the FTIR cannot be as high as the temperature that can be a chieved 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 des cribed for performing TGA-FTIR measurements at reduced pressures, which sig nificantly improves the gas Row characteristics of the system for high boil ing compounds. It is shown that reduced pressure also minimizes sample carr yover, and reduces or eliminates trapping of material in the transfer line. Data are also presented that show that using the pressure as an experiment al parameter can yield additional information about the structure of a samp le, and about the thermal decomposition process. (C) 2001 Elsevier Science B.V. All rights reserved.