Poly(dimethyl siloxane)-grafted black phosphorus nanosheets as filler to enhance moisture-resistance and flame-retardancy of thermoplastic polyurethane

Abstract

Towards simultaneously improving the moist ambient stability and flame retardancy efficiency of black phosphorus (BP) nanosheets, cross-linked polydimethylsiloxane (PDMS) is simultaneously synthesized and grafted onto the surface of BP nanosheets, thus obtaining hydrophobicity to shield the water molecule and synergistic flame retardant effect. Compared to badly damaged morphology of pure BP nanosheets, the well-ordered crystal structure confirms that PDMS-BP nanosheets are moist-environmentally stable. With the grafting of PDMS, BP nanosheets present higher flame retardancy efficiency to thermoplastic polyurethane (TPU). The reductions of 59.6% and 14.3% are presented in peak heat release rate (PHRR) and total heat release (THR) of TPU resin, compared with pure TPU. The CO2 and CO produced by resin combustion are also decreased by 42.8% and 29.3%, indicating lower gas toxicity. Based on the morphology observation and element analysis of char residue, the synergistic effect between phosphorus and silicon elements is responsible for the flame retardancy improvement. Such a route simultaneously provides a valuable reference for moist-environmentally unstable nanomaterials and develops the practical application of BP nanosheets in polymer composites fields.