A bio-based dual-effect iron-derived supermolecule enabling fire-safe and mechanically reinforced epoxy

A balanced enhancement of anti-flammability, smoke suppression and mechanical property of thermosetting epoxy merely via a phosphorus/nitrogen-free catalytic mode was a vigorous challenge. To attain this goal, we put forward a simultaneous optimizing strategy via integrating the vapor/condensed-phase sensitive dual-effect iron-catalytic structures into polymeric supermolecule. A radical co -polymerization was executed on specific host-guest vinyl cyclodextrin/ferrocene (VCD@Ferr) and co-monomer acrylic acid, followed by a complexation with Fe 3+ to synthesize a bio-based iron-derived supermolecule (VCD@Ferr-AA-Fe). Various characterizations verified the target structure. An incorporation of merely 2 wt% VCD@Ferr-AA-Fe4:1 (iron loading 0.085 wt%) resulted in a UL-94 V-1 and a LOI of 27.9 % with total smoke production and peak smoke production rate decreased by 31.3 % and 33.6 %, respectively. A series of experiments evidenced a presence of intra-molecular synergistic effect between VCD@Ferr and AA-Fe component. In a proposed mechanism, iron ions of VCD@Ferr-AA-Fe4:1 coordinated with degraded products of epoxy to increase the melt viscosity, followed by a combined catalytic charring behavior. Additionally, the released ferrocene participated into the vapor-phase flame inhibition and smoke suppression. Besides, flexural and unnotched impact strength were respectively increased by 37.3 % and 39.5 % without a loss of tensile strength. Prospectively, a bio-based dual-effect structure exploited a P/N-free highly efficient route towards fire-safe polymers.