Graphitic carbon nitride/phosphorus-rich aluminum phosphinates hybrids as smoke suppressants and flame retardants for...

Graphitic carbon nitride/organic aluminum hypophosphites (g-C₃N₄/OAHPi) hybrids, i.e., CPDCPAHPi and CBPODAHPi, were synthesized by esterification and salification reactions, and then incorporated into polystyrene (PS) to prepare composites through a melt blending method. Structure and morphology characterizations demonstrated the successful synthesis of PDCPAHPi, BPODAHPi and their hybrids. The g-C₃N₄ protected OAHPi from external heat and thus improved the thermal stability of OAHPi. Combining g-C₃N₄ with OAHPi contributed to reduction in peak of heat release rate, total heat release and smoke production rate of PS matrix. Reduced smoke released has also been demonstrated by smoke density chamber testing. Additionally, introduction of the hybrids led to decreased release of flammable aromatic compounds. These properties improvement could be attributed to gas phase action and physical barrier effect in condensed phase: phosphorus-containing low-energy radicals generated from OAHPi effectively captured high-energy free-radicals evolved from PS; g-C₃N₄ nanosheets retarded the permeation of heat and the escape of volatile degradation products. Therefore, g-C₃N₄/OAHPi hybrids will provide a potential strategy to reduce the fire hazards of PS.