Correlation between dynamic mechanical properties and infrared spectra of HTPB propellant during aging

The characteristic absorption peaks of the infrared spectrum correspond to different functional groups and chemical bonds. The infrared qualitative analysis of the functional groups can be carried out by analyzing the position of the characteristic peaks of the spectrum, and the quantitative analysis of the functional groups can be carried out by analyzing the peaks. In order to study the aging performance of hydroxyl-terminated polybutadiene (HTPB) propellants from the perspective of infrared spectrum, HTPB propellants under accelerated aging at 70℃ were tested for both their dynamic mechanical properties and Fourier transform infrared spectrum. The loss factor curves, tanδ, obtained from dynamic thermomechanical analysis (DMA) were used for analyzing the aging rule of dynamic mechanical properties. For infrared spectrum, spectral subtraction was used to get the characteristics peak during aging process, by which the corresponding functional groups can be found to analyze the aging mechanism. Further, in order to quantitatively characterize the aging of HTPB propellant by using infrared spectra, second derivative data conversion was used to eliminate the interfering factors on spectrum such as ambient temperature and instrument. The correlation between peak value of peak α in loss factor curve and infrared spectra was analyzed, then. The results show that peaks at wavenumber 3600cm^-1-3100cm^-1(-OH), 1186cm^-1(C-O-C), 885cm^-1(epoxy structures) and 1650cm^-1(C=O) of FTIR spectrum second-order derivative have high linear correlation to peak value of peak α. The conclusion obtained from the correlation analysis is consistent with the oxidative crosslinking mechanism in the aging process of HTPB, which confirms the feasibility of quantitative characterization of propellant aging by infrared spectrum.