ABSTRACT To address the flammability issue of rigid polyurethane foam (RPUF) and the resource utilization challenge of OG sludge from converters, this study innovatively introduced melamine polyphosphate (MPP) and OG sludge to construct a synergistic flame retardant system, successfully preparing RPUF/OG/MPP composite materials. And its thermal stability, physical properties and combustion performance were systematically studied. Meanwhile, its PHRR and smoke factor (SF) decreased by 42.73% and 48.24%, respectively. Analysis of the char layer reveals that the RPUF composite with OG sludge forms a dense and continuous carbon layer during combustion, which can effectively inhibit heat transfer and flammable gas diffusion. Based on this, a plausible gas‐phase/condensed‐phase synergistic flame‐retardant mechanism for RPUF/MPP/OG composites is proposed. This research not only enhances the flame‐retardant performance of RPUF but also achieves resource utilization of OG sludge solid waste, offering a feasible approach to address the dual challenges of material flammability and solid waste management. It holds broad application prospects in building insulation materials and resource recycling sectors.
Zhang et al. (2026) studied this question.