P-N hybrids modified with MXene encapsulation significantly improve fire safety properties of rigid polyurethane foams

In recent years, P-N based hybrids flame retardants have received more and more attention in the field of fire safety due to their synergistic effect in the gas and condensed phases, which makes it easy to achieve efficient flame retardancy. However, their flame retardant mechanism in the gas phase rests more on the increase of non-flammable gases than on the conversion of harmful gases to harmless gases, and their hybrids are often not sufficiently stable. Therefore, in this study, P-N hybrids were encapsulated and modified using MXene, which has high thermal stability and outstanding catalytic ability, to prepare a novel flame-retardant hybrid, MDAPP, which was incorporated into rigid polyurethane foam (RPUF) to achieve more efficient fire safety performance. The results showed that MDAPP significantly enhanced the fire safety properties of RPUF composites. Specifically, RPUF-2.0MDAPP resulted in 40.98%, 63.16, and 60.00% decreases in total heat release (THR), total smoke release (TSP), and CO production rate (COPR) of RPUF, respectively. Moreover, the system also achieves synergistic flame retardant effects in the gas and condensed phases. At the same time, RPUF-2.0MDAPP has excellent thermal shielding performance, with a temperature reduction of 88.14% compared to RPUF in a fire source heating test when placed in a vertical position. In addition, the compressive strength and hydrophobicity of RPUF-2.0MDAPP have been improved to ensure its longevity in complex environments. This study proposes a solution to the problem of reducing the fire risk of RPUFs and promotes the widespread use of RPUF.