Pressure-dependent pyrolysis regulation and flame retardancy of polyethylene enabled by MXene/Co3O4 nanohybrids

Polyethylene (PE) exhibits aggravated fire hazards under sub-atmospheric conditions due to pressure-induced alterations in pyrolysis kinetics and volatile-release behavior. In this work, a pressure-adaptive flame-retardant PE composite was constructed by introducing an MXene-anchored Co 3 O 4 nanohybrid. The FRPE-MXene/Co 3 O 4 composite shows superior flame-retardant and thermal stability compared with other systems. Its total heat release (35.4 MJ/m 2 ) is 46.29% lower than pure FRPE (66.0 MJ/m 2 ). The reduced total CO release (0.77 g), 65.99% increase in residual mass, together with an approximately 20% reduction in smoke density, confirms the enhanced carbonization capability and improved fire safety performance of the material. Moreover, the LOI value reaches 29.6 ± 0.48%, higher than FRPE-MXene (27.1 ± 0.63%) and FRPE-Co 3 O 4 (27.8 ± 0.63%), demonstrating the enhanced flame-retardant efficiency of the hybrid filler system. Microscopic and XPS analyses reveal that the nanohybrid facilitates deeper deoxygenation, enhanced aromatization, and the formation of dense, graphitized char, thereby significantly improving the structural integrity of the condensed phase. Conventional flame-retardant polyethylene exhibits unstable pyrolysis and incomplete oxidation under low-pressure (55 kPa) combustion, leading to excessive hydrocarbon release and poor char formation. SVUV-PIMS analysis shows that introducing the MXene/Co 3 O 4 hybrid system effectively suppresses radical-induced chain scission and enhances char formation, thereby improving combustion stability and flame-retardant efficiency under low pressure. These findings establish a dual catalytic-barrier flame-retardant mechanism, wherein MXene enables efficient heat dissipation and volatile confinement, while Co 3 O 4 promotes redox-driven carbonization. This work provides an effective strategy for designing high-performance flame-retardant polymers suited to low-pressure environments.