High-Strength, Flame-Retardant, UV-Resistant Polyurethane Elastomers Realized by Synergizing Nitrogen-Phosphorus-Containing Ligands and Cerium Oxide Nanoparticles

High fire safety, aging resistance, and excellent mechanical properties are particularly important for polyurethane elastomers in electronic encapsulation and membrane materials. Here, we synthesized a polyurethane elastomer material with enhanced mechanical properties, as well as better fire safety and UV aging resistance through the design of nitrogen and phosphorus-containing elemental chain extenders (BFPP and AHMT) and the incorporation of cerium oxide nanoparticles. Sample APU-BFPP-4 spiked with 1.25% AHMT, 2.5% BHPP, and 5% cerium oxide nanoparticles can pass the UL-94 V-0 rating and the LOI increases to 27.5%. The PHRR and THR of the APU-BFPP composites were lower than those of PU by 6.42% and 14.56%, respectively. Meanwhile, the addition of cerium oxide nanoparticles can effectively improve the UV shielding and mechanical properties of polyurethanes; the APU-BFPP composites can achieve 100% UV shielding in the full UV band, and the mechanical properties can reach 30 MPa. In order to investigate the flame-retardant mechanism, the condensed phase and gas phases of PU elastomer combustion have been analyzed; the results showed that the flame-retardant mode of the APU-BFPP composites was mainly dominated by the trapping of fuel free radicals and the carbon layer blocking effect. Compared with the flame-retardant PU composites that have been reported, APU-BFPP composites have achieved a better balance between efficient flame retardancy, UV protection properties, and good mechanical properties, which makes it perform well in electronic encapsulation and membrane materials.