Introducing Students to Thermogravimetry Coupled with Fourier Transform Infrared Spectroscopy

Thermogravimetry coupled with Fourier transform infrared spectroscopy (TG-FTIR) is a useful technique for the thermal and structural characterization of materials at academic and research levels. This paper describes an experiment for chemistry students to understand the use of TG-FTIR for advanced qualitative and quantitative thermal analysis using a natural compound as a sample. In the classroom, students learned about the fundamental principle of thermal analysis, TG-FTIR instrumentation, and different applications of this coupled technique for materials characterization. In the laboratory, students received a description of each part of the TG-FTIR system, as well as how to tune the system and to develop a method. The primary objective of the experiment was to guide them in the interpretation of results including thermograms, infrared spectra, DSC, and Gram Schmidt (GS) curves. For this, students prepared and analyzed cellulose fibers extracted from pineapple leaves and a mixture of them with sodium hydroxide (NaOH) and monoethanolamine (MEA). Students were initially instructed to study the TG, DSC, and Gram Schmidt curves and to identify the temperatures at which the most significant mass changes occurred. Then, they focused on analyzing the infrared spectra obtained at each temperature range. This practice allowed them to identify the gases emitted during fiber decomposition and the volatile character of the MEA as well as to corroborate the MEA presence in the fiber/MEA mixture. This procedure can be adapted to guide students in the analysis of pure substances and mixtures.