Facile fabrication of organically modified boron nitride nanosheets and its effect on the thermal stability, flame retardant, and mechanical properties of thermoplastic polyurethane

Although hexagonal boron nitride (h-BN) has presented a potential prospect in polymer composite fields, undesirable interfacial interaction with polymer matrix that generates serious aggregation of nanomaterials has suppressed its enhancement effect. Moreover, the chemically inert surface of h-BN also makes the commonly used approach that improves the interfacial interaction between nanofillers and polymeric matrix invalid. Herein, the functionalized modification of chemically inert h-BN was successfully fabricated by the adsorption of cetyl-trimethylammonium bromide, with electrostatic interactions. The obtained h-BN (cetyl-trimethylammonium bromide-BN) was well characterized by systematic tests and then added into thermoplastic polyurethane (TPU) matrix. The inclusion of functionalized h-BN can dramatically improve thermal stability, flame retardant, and mechanical properties of TPU composites. With the incorporation of as low as 4.0 wt% nanofillers, maximal value of heat release rate and total heat release of TPU were reduced by 57.5% and 17.8%, compared with those of pure TPU, respectively. Moreover, tensile strength of TPU composite with a loading of 2.0 wt% was increased by 79.3% in comparison with that of neat TPU. The facile functionalized approach of chemically inert h-BN paves the way for promising applications of h-BN in the development of flame retardant polymer materials.