Silane-functional benzoxazine: synthesis, polymerization kinetics and thermal stability

A benzoxazine with siloxane and phenyl sulfone units (BS-b) is synthesized by using aminopropyltriethoxysilane, 4, 4'-dihydroxydiphenylsulfone and paraformaldehyde as precursors via Mannich condensation. Then the hydrolysis and polycondensation reactions of siloxane units are performed and benzoxazine bearing polysiloxanes (BS-PSO) is obtained. The ring-opening polymerization reactions of both BS-b and BS-PSO are studied by FTIR and differential scanning calorimetry (DSC) in nonisothermal conditions. The kinetics of the polymerization of BS-b is found to be well described by using an nth-order kinetic model for n = 0.7 (activation energy = 141 kJ∙mol−1). The BS-PSO is also used to modify bisphenol-A-based benzoxazines (BA-a), and the morphological structure and thermal properties of the copolymer are investigated. The thermogravimetric analysis results indicate that the silane-functional polybenzoxazines display enhanced initial decomposition temperature and char yields in comparison with the poly(BA-a). These results are believed to be important for the development of new flame-retardant laminates.