High-efficient fire-safe epoxy enabled by bio-based atomic-level catalytic engineering

Abstract

It is a considerable challenge to synchronically attain a pronounced fire safety of polymers with reinforced multifunctions solely via a simple catalysis manipulation. The host–guest complex (CD@Ferr) was relatively greenly elaborated to concurrently incorporate atomic-level catalysis and bio-based flexible charring precursor. A delayed release of ferrocene to above 150 °C was evidenced due to a weak trapping effect. 2 wt% CD@Ferr (i.e., an unprecedentedly low iron loading of 0.008 wt%) endowed epoxy with UL-94V-0 rating and limiting oxygen index of 28.3%, together with a reduced total smoke production by 20.3%. Through a systematic mechanism investigation, a portion of ferrocene generated iron radicals to participate in a condensed-phase macro-radical quenching. The resultant atomic-level irons vigorously catalyzed a polyaromatic reaction of rigid-flexible epoxy/cyclodextrin precursors. In parallel, some ferrocene released into vapor phase was conversed to iron radicals for quenching H·/HO·. The evolved atomic-level iron compounds remarkably catalyzed the thermal oxidation of soot in the vapor phase. Intriguingly, a synchronically enhanced tensile strength and impact toughness by respective 30.4% and 85.8% were observed with an increased glass transition temperature by 24 °C owing to the weak hydrogen-bond interplay between β-CD and epoxy. Prospectively, a P/N/Si-free dual-phase successive atomic-level catalysis exploits a novel roadmap towards high-efficient fire safety and multifunctionality.