Harnessing MOF-derived homogeneous hierarchical nickel phyllosilicate for epoxy composites: breaking the dilemma between flame retardancy and mechanical and tribological properties via co-deploying polyphosphazene and DOPO

Abstract

Epoxy resin (EP) is a widely utilized thermosetting resin in structural and functional materials; however, achieving a delicate balance between flame retardancy and stress-sensitive properties remains a significant challenge. Herein, a multifunctional flameretardant strategy was rationally designed by incorporating polyphosphazene-decorated hierarchical nickel phyllosilicate (NiPS@PZN) as a reinforcing and wear-resistant filler while 9,10-dihydro-9-oxa-10-phospaphenanthrene-10-oxide (DOPO) as a flame-retardant synergist. Results demonstrate that the synergistic incorporation of NiPS@PZN and DOPO (1:1 mass ratio) at a total loading of 6% endows the EP composites with a UL-94 V-0 rating and elevates the limited oxygen index to 26.6%. This hybrid system also suppresses the total heat release, total smoke production, and carbon dioxide production by 10.4%, 23.2%, and 26.8%, respectively. The formation of a continuous and dense char layer confirms a dual-phase flame-retardant mechanism involving both condensed and gaseous phases. Moreover, the synergistic effect of NiPS@PZN and DOPO facilitates the concurrent optimization of mechanical and tribological properties, remarkably increasing the tensile strength to 103.5 MPa and achieving a minimum wear rate of 1.78 × 10⁻⁵ mm³ · N⁻¹ · m⁻¹. This study offers a viable pathway for the rational design of multifunctional additives and the fabrication of high-performance composites.