Tough, high-strength, flame-retardant and recyclable polyurethane elastomers based on dynamic borate acid esters
Tiantian Zhang, Siqi Huo, Guofeng Ye, Cheng Wang, Qi Zhang, Zhitian Liu
Abstract
With the wide application of polyurethane elastomers , it is necessary to develop recyclable, fire-retardant polyurethane elastomers with great mechanical properties to comply with industrial requirements. Herein, we fabricated a flame-retardant, recyclable, strong yet tough polyurethane elastomer (PIDB-1) based on dynamic borate acid esters. The introduction of phosphaphenanthrene and boron-containing groups endow PIDB-1 with great flame retardancy, as reflected by it achieving the vertical burning (UL-94) V -0 rating. The PIDB-1 film shows high visible light transmittance, and its transmittance reaches 90 % at the wavelength of 800 to 900 nm. The tensile strength of PIDB-1 is 54.9 MPa, and its toughness reaches 207.8 kJ/m 3 , indicative of superior mechanical properties. Meanwhile, the dynamic borate acid esters allow the PIDB-1 elastomer to possess physical and chemical recyclability. When using PIDB-1 as a polymer matrix for carbon fiber-reinforced polymer composites , the carbon fibers can be fully recycled. This work provides an integrated design strategy for creating transparent, flame-retardant, recyclable polyurethane elastomers combining high strength and toughness based on dynamic borate ester bonds, which is expected to find wide applications in different industries.