Cobalt/copper coordinated organic-inorganic hybrid fibrous phosphorus-nitrogen flame retardant: Simultaneously improving fire safety, deicing and mechanical properties for thermoplastic polyurethane

Abstract

Thermoplastic polyurethane (TPU), a commonly used cable wrapping material for new energy vehicles and charging stations but faces the limitation of high fire hazard. However, conventional synthesis strategies of flame retardants (FRs) often fail to achieve the enhancement of the combination of fundamental properties of TPU, including flame retardancy, melt dropping resistance, stretchability, and toughness, which are necessary for practical applications. Herein, a novel strategy for the synthesis of a cobalt/copper coordinated organic-inorganic hybrid fibrous phosphorus-nitrogen FR (CoCu/P–N) inspired by supramolecular aggregates is proposed and used as an additive for TPU. TPU composites containing CoCu/P–N (TPU-CoCu/P–N) exhibited remarkable improvements in fire safety, melt dripping resistance, mechanical properties, and deicing performance. Cone calorimeter tests (CCT) revealed that TPU-6CoCu/P–N achieved substantial reductions in peak heat release rate (pHRR), total smoke production (TSP), and total carbon monoxide production (TCOP) values by 65.2 %, 74.2 %, and 59.3 %, respectively, compared to pure TPU. Notably, only 2 wt% CoCu/P–N enabled TPU composite to achieve UL-94 V-0 rating. Additionally, ice on the surface of TPU-6CoCu/P–N melted and slid off significantly faster. Furthermore, TPU-6CoCu/P–N demonstrated a high tensile strength of 36.48 MPa and an elongation at break of 878.94 %. Through comprehensive characterization and analysis, the underlying mechanisms responsible for the enhanced multifunctional performance of TPU-CoCu/P–N were elucidated. This work provides valuable insights and strategies for the design of advanced FRs, contributing to the development of safer high-performance TPU composites.