Thermal degradation behavior and mechanism of polybenzoxazine based on bisphenol-S and methylamine

The thermal degradation behavior of polybenzoxazine based on bisphenol-S/methylamine was studied by Fourier transform infrared spectroscopy, thermogravimetry–mass spectrometry, and differential thermal analysis in air and in inert atmospheres, respectively. A multi-step mass loss process is observed in the non-isothermal degradation in air and in inert atmospheres, and the char yield is about 54 % at 800 °C in nitrogen, whereas almost no degradation residue is remained at 660 °C in air. The main gaseous products are SO2, SO, and CO2 corresponding to the scission of the aromatic C–S bond and the Mannich bridge structure. The onset of the aromatic C–S bond scission is at 315 °C, and the reaction ends at 630 °C. The cleavage of the C–N and aromatic C–C bonds in the Mannich bridge structure takes place in the temperature range of 330–660 °C.