Construction of transition metal aromatic-sulfide polyphosphazene heterostructured nanowires for synergistic flame retardancy and smoke suppression

To efficiently enhance the fire safety of epoxy resin (EP), a novel core–shell organic–inorganic hybrid nanowires based on copper aromatic-sulfide and polyphosphazene heterostructure were designed and synthesized via a two-step synthesis, including the synthesis of 2,4-dichlorothiophenol-Cu (Cl-Cu) nanowires and the in-situ coating of poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) on Cl-Cu nanowires ([email protected]). With only 0.5 wt% of [email protected] nanowires, the limited oxide index (LOI) of EP was increased to a maximum of 27.4 %. The combustion performance of EP with 0.5 wt% [email protected] nanowires investigated by cone calorimeter tests showed that the peak of heat release rate (PHRR), and total smoke production (TSP) decreased by 24.50 %, and 22.73 %, respectively, and the residue mass increased by 135.82 %. Moreover, 0.5 wt% addition of [email protected] nanowires dramatically enhanced the tensile strength of EP by 34.9 %, elongation at the break by 27.6 %, and impact strength by 14.2 % due to the unique 1D organic–inorganic nanowire structure. It was inferred that [email protected] nanowires possessed significant synergistic effect on the improvement of flame retardancy, smoke suppression and mechanical strength.