Interface construction of phosphorus-based hybrid with micro/nano hierarchical structure toward intumescent flame-retardant epoxy resins with robust mechanical properties

•Phosphorus-based hybrid with micro/nano hierarchical structure was constructed.•EP containing phosphorus-based hybrid showed high fire safety.•EP with phosphorus-based hybrid possessed comparable glass transition temperatures.•The mechanical properties of EP with phosphorus-based hybrid were superior to EP. The facile strategy for constructing phosphorus-based hybrid (APP@Zn-PT) is proposed to the simultaneous optimization of flame-retardant properties and mechanical properties of epoxy resins (EP), which is a long-term concern for the intumescent flame-retardant systems. Herein, APP@Zn-PT was fabricated via the assembly of nano-sheet phosphorus-containing triazole-zinc complex (Zn-PT) on the surface of ammonium polyphosphate micro-particles (APP). Notably, EP modified with APP@Zn-PT synchronously displayed highly fire-safe performance and excellent mechanical properties, which is seldom found in the traditionally intumescent flame-retardant EP systems. In the presence of 7 wt% APP@Zn-PT, EP acquired a high limiting oxygen index (LOI) of 31.1 %, and succeeded to meet the requirement for a UL-94 V-0 rating. Meanwhile, the results of cone calorimeter test (CCT) showed that the crucial parameters involving smoke production and heat release of EP/APP@Zn-PT presented significant decrease, that total smoke production (TSP) was dropped from 55.7 m2 of EP to 36.2 m2, and the peak of heat release rate (PHRR) was decreased from 1156 to 384 kW/m2. In addition, the interfacial interaction of APP@Zn-PT in epoxy matrix was improved as compared to APP due to the embedment of nano-sheet Zn-PT, which possessed reinforcing effect as well, and thereby the mechanical performances of EP/APP@Zn-PT were superior to neat EP and EP/APP. Generally, this work lays a foundation for the construction of phosphorus-based micro-nano hybrids, showing a great potential in high-performance polymers for practical application.