Enhancing flame retardancy of ethylene-vinyl acetate composites via non-covalent functionalization of black phosphorus nanosheets

The development of flame-retardant polymer materials is essential for reducing fire hazards and protecting lives and property. Black phosphorus shows promise as a flame retardant but suffers from poor dispersion in polymer matrices. This study presents a method for preparing non-covalently functionalized black phosphorus nanosheets (BP) through composite modification with an ionic liquid (IL) and pentaerythritol phosphate (PEPA), forming IPBP, which was incorporated into an ethylene-vinyl acetate (EVA) matrix to improve both mechanical properties and flame resistance. Molecular Dynamics simulations indicate that EVA enhances interfacial interactions between IL, PEPA, and BP, resulting in stronger interaction energies and better diffusion rates. Experimental results confirm that IPBP nanosheets improve BP compatibility with EVA. Combustion tests show that a 1.5 wt.% IPBP/EVA composite achieved a V-0 rating in the UL-94 test, reducing total heat release (THR) and peak heat release rate (PHRR) by 35.9% and 35.5%, respectively. Moreover, the tensile yield stress of IPBP/EVA increased by 23.3% and 10.8% with 0.5 and 1.0 wt.% IPBP, while that with 1.5 wt.% IPBP is comparable to pure EVA resin. This work provides an effective strategy for designing flame retardants to improve the fire resistance of EVA materials.