ENHANCEMENT IN THE FIRE RESISTANT EFFICIENCY OF EPOXY RESIN BY SYNERGISTIC EFFECT BETWEEN METAL-ORGANIC FRAMEWORKS AND POLYETHYLENEIMINEMODIFIED AMMONIUM POLYPHOSPHATE

Abstract

Two metal-organic frameworks (MOFs), including ZIF-67 and ZIF-8, were successfully synthesized through self-assembly of organic bridging ligands and transition metal ions. Additionally, the MOFs were introduced into an intumescent flame-retardant epoxy composite containing polyethyleneimine-modified ammoniumpolyphosphate (APP@PEI). The synergistic effects between MOFs and APP@PEI on the flame retardancy and thermal stability of the epoxy matrix were found. Speciallythe incorporation of ZIF-8 provied a superior enhancement in the fire resistance of the composite. The nanocomposite loading 3 wt% ZIF-8 and 7 wt% APP@PEI passeda V-0 rating in the UL-94 vertical burning test with a limiting oxygen index value of 30.3%. The formation of thermally stable metal phosphate compounds played acrucial role in improving the condensed-phase flame retardant efficiency of the nanocomposites, which reinforced the surface structure of the char layer to become morecontinuous and compact. Moreover, tensile and impact tests revealed that the presence of MOFs significantly improved the mechanical properties of the composite containing APP@PEI. This combination offered a promising approach for developing high-performance intumescent flame-retardant epoxy materials.