Mxene nanohybrids assembled with phytic acid-modified UiO-66 toward mechanically reinforced, fire-resistant and Smoke-suppressed epoxy composites

Abstract

Given the good structural and compositional characteristics, there are considerable trends towards optimizing the architectures of two-dimensional materials to work for high-performance flame-retardant polymeric materials. Herein, considering the promising features of Ti₃C₂T_x MXene, phytic acid-modified UiO-66 (PA-UIO) was self-assembled onto MXene nanosheets (MXene/PA-UIO) using electrostatic interactions. The resulting nanohybrids presented good interfacial interactions and dispersion in epoxy matrix, opening up the possibility of simultaneously improving the mechanical and flame-retardant properties of the composites. Consequently, epoxy composites with 2 wt% MXene/PA-UIO achieved elevated mechanical properties and enhanced thermal properties, reflected by the increased storage modulus and tensile strength, as well as the declined rate of mass loss (R_max, 28.3% reduction rate). Also, the addition of MXene/PA-UIO nanohybrids led to the drops in peak heat release rate (PHRR), peak smoke production rate (PSPR), peak CO production rate (PCOP) and peak CO₂ production rate (PCO₂P) of 32.0%, 36.5%, 33.8% and 38.6% respectively, compared to those of pure epoxy. Meanwhile, a smoke factor (SF) with 47% drop rate was obtained, accompanied by significantly decreased gas-phase products, verifying the superior heat-reducing, smoke-suppressing and toxic fume-attenuating effects of the nanohybrids. The synergistic effects between MXene and PA-UIO realized the “3-in-1” fire-safety epoxy nanocomposites in mechanical properties, flame retardancy and smoke/toxic fume-suppressing effects. The performance enhancement was mainly attributed to the dehydration charring of phosphorus-containing acid, catalytic charring of transition metal derivatives, quenching effects of phosphorus radicals and dilution of non-flammable gases, as well as the barrier effects of the nanosheets.