Thermal degradation behavior and kinetics of polybenzoxazine based on bisphenol-S and aniline

The thermal degradation behavior of polybenzoxazine based on bisphenol-S/aniline was studied by Fourier transform infrared spectroscopy, thermogravimetry–mass spectrometry, thermogravimetry, and differential thermal analysis. The degradation reaction begins with the detachment of Schiff base, then the scission of aromatic C–S bond, followed by the cleavage of Mannich bridge structure. The scission pathways of the aromatic C–S bond in argon and air are similar, while the degradation pathways of the Mannich bridge structure in both atmospheres are different. The degradation of PBS-a shows two weight loss stages in nitrogen and air, respectively, and the kinetic parameters of the degradation in the first stage were obtained with Flynn–Wall–Ozawa and Coats–Redfern methods. The most probable kinetic mechanism function is a three-dimensional diffusion model in the initial stage in both nitrogen and air.