Construction of an organic iron phosphate/graphite carbon nitride hybrid system for improved fire safety of epoxy resin

Abstract

Enhancing the fire safety of epoxy resin (EP) is crucial due to its widespread but inherent flammability, necessitating the integration of additive flame retardants (FRs) that are effective in small quantities and exhibit efficient flame retardancy. This study constructed a novel, efficient FR by synthesizing organic iron phosphate (ATMP-Fe) and loading it on graphitic carbon nitride (g-C3N4). The resulting hybrid flame retardant (ATMP-Fe/g-C3N4) was added to EP in minimal amount to bolster its flame retardancy and safety features. Incorporating a mere 3 wt% of ATMP-Fe/g-C3N4 into EP significantly improved its flame retardancy and thermal stability. This was evidenced by an increase in the limiting oxygen index from 25.5% for EP to 30.1%, achieving a V-1 rating in the UL-94 test, and producing a 22.0 wt% char residue. Moreover, there was a substantial reduction in peak heat release rate, total heat release, and total smoke production by 36.3%, 27.5%, and 39.3%, respectively. The reduction in pyrolysis products, along with the formation of a dense and stable char layer facilitated by the synergistic effects of phosphorus and iron elements, significantly improved the fire safety of EP. Additionally, the enhanced hydrophobicity, mechanical properties, and electrical conductivity of the EP/3ATMP-Fe/g-C3N4 composite suggested potential for wider application of EP in various fields.