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 A degrees C in nitrogen, whereas almost no degradation residue is remained at 660 A degrees 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 A degrees C, and the reaction ends at 630 A degrees 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 A degrees C.