Enhancement of Flame Retardancy, Mechanical Properties, and Hydrolysis Resistance of TPU by Phosphoramide Aggregates

In this study, a polymeric flame retardant named TPOP was synthesized from POP and triglycidyl isocyanurate and applied to TPU. Compared with POP, TPOP provided better flame retardancy, achieving a higher LOI of 26.8% for TPU/15TPOP. After soaking in hot water at 85°C for 192 h, TPU/15TPOP also showed superior retention of flame retardancy. Cone calorimetry tests (CCTs) showed that 15% TPOP reduced the PHRR, THR, and TSR of TPU by 63.1%, 53.1%, and 23.4%, respectively, and increased the char yield from 6% to 30.5%. A denser and more continuous char layer observed in SEM images, along with improved thermal insulation and a lower back‐side temperature revealed by infrared thermal imaging, confirmed the enhanced condensed‐phase barrier effect of TPOP. Moreover, incorporating TPOP raises the tensile strength from 33.7 to 36.5 MPa while maintaining elongation. The transparency of TPU was also well preserved, with the composite showing 63.2% transmittance and 3.9% haze after the addition of TPOP.