Superior thermal stability and smoke suppression of epoxy resin composites with graphene/LDH phosphorus-rich hybrids

In this article, graphene/LDH phosphorus-rich triple hybrid was prepared by a mild method and used to effectively improve the thermal stability and smoke suppression of epoxy resin (EP). The graphene was firstly reacted with hexamethylenediamine (HA) and followed by the treatment with the layered double hydroxide (LDH) and NaH₂PO₄ solutions. Compared to the unmodified graphene, the initial decomposition temperature of the triple hybrids increases significantly from 168.6 to 292.5°C. The residual carbon content is greatly improved and the residual mass is up to 84.1%. Elemental analysis reveals the content of phosphorus in EP composites is as high as 10 wt%. In flame retardancy tests, the peak heat release rate of the EP composite with 5 wt% graphene/LDH phosphorus-rich hybrids decreases to 786.15 KW/m², 41.19% drastic reduction compared to that of EP. These results indicate that the triple functionalization process effectively expands the interval distribution of heat release and makes the heat release process more gradual and spread flames smaller. The smoke production rate and total smoke production rate of EP composite with 5 wt% graphene/LDH phosphorus-rich hybrids are 0.32 m²/s and 40.91 m², which are significantly reduced by 65.22 and 57.83%, respectively. This gentle and efficient process provides a new approach to multi-functional design to improve the thermal stability and smoke suppression of resin-based composites.