High-Strength, Recyclable, and Flame-Retardant Polyurethane Elastomers Enabled by Phosphorus Groups and Hydrogen Bonding

A persistent challenge in thermoplastic polyurethane elastomers (TPUs) used in fire-prone environments is reconciling high flame retardancy with a superior mechanical performance. To address this issue, a phosphorus-rich benzene-containing diol monomer (P-D) was designed and synthesized from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and terephthalaldehyde (TPA). Leveraging the synergistic effects of P-D and multiple hydrogen bonds, we successfully prepared a high-performance polyurethane elastomer, designated PD–PU-3. Compared with the baseline polyurethane (BPU), PD–PU-3 incorporating the P-D monomer exhibited significantly enhanced thermal stability. The incorporation of multiple hydrogen bonds markedly improved mechanical performance, achieving a tensile strength of 31.4 MPa and a toughness of 282.08 MJ·m–3. In terms of flame retardancy, PD–PU-3 exhibited outstanding intrinsic properties, with a limiting oxygen index (LOI) of 29.2% and successful achievement of the UL-94 V-0 rating. Furthermore, PD–PU-3 demonstrated excellent recyclability and favorable processing characteristics. This study provides a strategy for fabricating high-performance, intrinsically flame-retardant polyurethane elastomers with enhanced practical applicability. The developed materials hold broad potential for applications in fire-resistant coatings, aerospace components, and construction fireproofing.