A benzimidazolyl-substituted cyclotriphosphazene and its application in benzoxazine: Curing behaviors, thermal properties, and fire safety

In this study, a well-designed benzimidazolyl-substituted cyclotriphosphazene (BICP) was used as a versatile additive to enhance the integrated performances of bisphenol A-aniline based benzoxazine (BA-a). Our results showed that the BA-a/BICP systems possessed lower curing temperature than virgin BA-a due to the catalytic action of tertiary amines in BICP. Moreover, the thermal resistance of BA-a/BICP thermosets was better than that of BA-a thermoset because of the rigid structure and high thermal stability of BICP. The introduction of BICP significantly enhanced the fire safety of BA-a. For instance, the limiting oxygen index and UL-94 rating of BA-a/BICP-11 sample with 11 wt% of BICP were up to 35.2% and V-0. Compared with BA-a, the total smoke production and peak smoke production rate of BA-a/BICP-17 sample with 17 wt% of BICP were reduced by 36.5% and 39.3%, respectively. The improved fire safety of BA-a/BICP sample was mainly due to the condensed-phase effect of BICP. This work provides a simple strategy for the development of advanced benzoxazine resins with low curing temperature, great thermal properties, and superior fire safety. Graphical