Pyrolysis of hybrid polyurethane inorganic thermal insulation: thermogravimetric analysis and FTIR spectra

Purpose. The purpose of this work is to study the process of thermal decomposition (pyrolysis) of two samples of a hybrid organic-inorganic (OIH) heat-insulating material based on data obtained by thermogravimetric analysis and IR-Fourier spectrometry. The goal set predetermined the following research tasks: to find out the basic chemical structure of the OIH samples (by functional groups), to study the order of processes in materials when heated in nitrogen, to calculate the activation energy, the pre-exponential factor, to determine the pyrolysis mechanism. Methods. The methods of thermogravimetric analysis and IR-Fourier spectrometry were used in the work. Samples for spectrometric analysis were prepared in the process of thermogravimetric tests using the “freezing” experiment method. Results and discussion. The paper studies the structural features of two samples of hybrid polyurethane inorganic (OIH) thermal insulation material and traces the physicochemical processes that occur when they are heated under dynamic conditions in a nitrogen atmosphere up to 750 °C. The multi-stage nature of the pyrolysis of the OIH material is shown. The pyrolysis of the first sample is a threestage process. For the second sample, decomposition proceeds in two stages. All stages are endothermic. This indicates the predominance of energy costs for breaking bonds between the organic and inorganic parts and other conclusions. It has been established that the pyrolysis of OIH samples at all stages is carried out according to the mechanism of nucleation and the growth of nuclei (active centers of destruction). Analysis of the IR spectra of the samples showed that both samples were prepared using Desmodur aliphatic isocyanates. Conclusions. The paper studies the chemical structure and physicochemical changes when heating the new group of materials — hybrid organic-inorganic (OIH) heat-insulating materials. The article is a continuation of a team of authors systematic study of a thermal behavior of modern types of polymer thermal insulation.