Superior radical scavenging and catalytic carbonization capacities of bioderived assembly modified ammonium polyphosphate as a mono-component intumescent flame retardant for epoxy resin

Combining biobased resources for fabricating intumescent flame retardant (IFR) systems is an promising approach for producing completely green flame retardants. Herein, ammonium polyphosphate (APP) particles were used as templates in the loading of an ATNi assembly on the basis of the electrostatic interactions among tannic acid (TA), adenine, and Ni2+ for the production of an all-in-one IFR (APP@ATNi). The incorporation of APP@ATNi can form hydrogen bonds in the EP matrix and improve the thermal conductivity and mechanical properties of the composites. When the mass of APP@ATNi reached 15 wt%, the EP composites had an LOI value of 33.5% and a V-0 rating. Total heat release and total smoke production were reduced by 29.1% and 47.2%, respectively. The HRR curves indicated the unique characteristics of the IFR system, and the characterization of condensed and gas phases showed that APP@ATNi formed a protective char layer. The bioderived assembly scavenged oxygen free radicals, catalyzed the formation of the char layer, and generated nonflammable gas, which protected the EP matrix during the combustion process. This study provides guidelines for designing bioderived IFR systems and is expected to promote the application of biobased resources in flame retardant production.

Automated summary

This study utilized APP@ATNi to prepare a multifunctional IFR system, enhancing the flame retardancy of composites and reducing smoke production and heat release during combustion, providing guidance for the design of bio-sourced flame retardant systems.