Preparation of novel and efficient arylphosphonate flame retardants for simultaneously enhancement of fire safety and UV-shielding properties of transparent thermoplastic polyurethane

Thermoplastic polyurethane (TPU) is highly flammable and UV aging, limiting its application in the field of new energy and electronic device. In this work, a novel macromolecular aromatic phosphonate Bis(4-(((diphenylphosphinyl)oxy)methyl)phenyl)phenylphosphonate (DMP) containing both P-C and P=O was successfully prepared by nucleophilic substitution reaction. The DMP was introduced into the TPU matrix to prepare multifunctional TPU composites. Condensed and gas phase analysis have shown that the flame retardant mechanism of DMP was mainly influenced by flame retardant inhibition and the barrier effect of char layer. Only 5 wt% DMP enabled TPU to obtain the UL-94V-0 rating with the LOI of 27.6 %. Compared with pure TPU, the HRR and THR of TPU/5 wt% DMP were decreased by 19.8 % and 13.2 %. Meanwhile, the matching of the melting point for DMP and the processing temperature for TPU increased its dispersion in TPU matrix. Due to the excellent compatibility between DMP and TPU, TPU/DMP composites almost retained their original transparency and ductility. In addition, TPU/DMP composites exhibited excellent UV resistance, obtaining 100 % UV shielding at UV-B wavelengths and up to 97 % UV isolation at UV-A wavelengths. The study introduced a novel approach for preparing multifunctional flame retardant additives, and opened up wide application prospects for high-performance flame retardant TPU composites in emerging fields such as rail transit and electronic packaging.