Preparation of cresyl diphenyl phosphate‐loaded halloysite nanotube composite and its flame retardancy in epoxy resin

Abstract To address the shortcomings of poor thermal stability, easy migration, and over‐plasticization of the liquid organic phosphorus flame retardant, cresyl diphenyl phosphate (CDP), we employed halloysite nanotube (HNT) as a carrier to load CDP, thus forming a novel composite (HNT‐CDP). The results demonstrated that the CDP loaded into HNT channels was 41 wt%. HNT‐CDP composites exhibited higher thermal stability, water resistance, and flame retardancy than mixtures of HNT and CDP in epoxy resin (EP). With a loading of 15 wt%, the limiting oxygen index of EP/HNT‐CDP increased to 48.3 and achieved a V‐0 rating in UL94 tests. Additionally, HNT‐CDP exhibited better inhibitory effects on the peak heat release rate and total heat release of EP, as well as a longer time to ignition, compared with the mixture. Moreover, as opposed to EP/HNT + CDP, EP/HNT‐CDP exhibited a significant 114.5% increase in tensile strength. These excellent thermal, water resistance, and mechanical properties can be primarily attributed to the loading of CDP by HNT channels. HNT effectively utilizes the channel confinement effect to isolate CDP from directly interacting with EP. The outstanding flame retardancy is mainly due to the synergistic effect between HNT and CDP after the formation of the composite.