Silane-grafted black phosphorus nanosheets via ball milling: Simultaneously enhanced flame retardancy and mechanical properties in polyurea composites
Qingshi Meng, Xinyu Liu, Shuangshan Li, Kai Wang, Lei Chen, Bin Wu, Sensen Han
Abstract
Conventional strategies for enhancing polymer flame retardancy face an intractable trade-off: high-loading additives inevitably sacrifice mechanical integrity and processability. To address this challenge, this study employed a novel silane coupling agent, (3-Isocyanatopropyl) trimethoxy silane (3IT), synthesizing modified black phosphorus nanosheets (M-BP) through a low-pollution mechanochemical approach using ball-milling grafting. Covalent surface engineering established covalent bonds and hydrogen bonds, enhancing interfacial bonding in BP/PUA composites. M-BP exhibited a markedly higher char yield (34.7 % at 700 °C) than neat BP, confirming that 3IT modification effectively improved BP's thermal stability and char-forming ability. As a result, when incorporated into the PUA matrix, the M-BP/PUA composite achieved approximately 9.5 times higher char residue than neat PUA, accompanied by reductions of 17.9 % in peak heat release rate (PHRR) and 8.5 % in total heat release (THR). The resultant M-BP/PUA composite preserved BP's excellent flame retardancy while exhibiting an 18.2 % increase in tensile strength, 6.6 % increase in impact strength, a 78.8 % increase in maximum tear force, and 94.7 % improvement in puncture resistance compared to unmodified BP composites. This research provides an innovative way for designing multifunctional flame retardants and creating high-performance polymers with high thermal stability, low flammability, and excellent mechanical properties, holding significant potential for practical applications.