Light stabilizer and diazo passivation of black phosphorus nanosheets: Covalent functionalization endows air stability and flame retadancy enhancements

Abstract As a new nano flame retardant, black phosphorus (BP) is easy to degrade and oxidize in the presence of water and oxygen, especially in the case of light, this process will be accelerated. In order to delay the oxidative degradation of BP and maintain its structure stability and flame retardant properties, the light stabilizer, free radical quenching type hindered amine is used to improve the ambient stability and the flame retardant efficiency of BP. In this work, BP was modified by diazotization to obtain active chlorine groups, and then the hindered amine light stabilizer was grafted onto the surface of BP through covalent reaction to form functionalized BP (BP-HAN). The fire risk of epoxy resin can be obviously reduced by introducing the BP-HAN into the matrix. The addition of 2 wt% BP-HAN can reduce the PHRR and THR value of epoxy by 56.0% and 48.2%, respectively. In particular, epoxy composites with only 0.5 wt% BP-HAN were able to achieve UL-94V-0 rating with an oxygen index of more than 30. In addition, compared with pure BP nanosheets, the ambient stability of BP modified by hindered amine was significantly improved. This work provides a reference for the application of BP in the field of flame retardant, and simultaneously achieves the improvement of the ambient stability and flame retardant performance of BP.