High-Performance TPE-S Modified by a Flame-Retardant System Based on Black Phosphorus Nanosheets

Few-layer black phosphorus nanosheets (BPs) combined with melamine cyanurate and poly(phenylene oxide) were used to prepare a flame-retardant thermoplastic elastomer based on polystyrene (TPE-S) for the first time. Compared with neat TPE-S, BP-modified TPE-S with a phosphorus content of 7.98% (TPE-S/BP-7.98) passed the UL-94 vertical burning V-0 rating, and the limiting oxygen index value increased to 24.0%. The peak heat release rate (PHRR), total heat release, and the average combustion effective heat of TPE-S/BP-7.98 were decreased by 61.8, 26.0, and 35.3%, respectively. The time to PHRR was increased from 90 s (neat TPE-S) to 170 s. Scanning electron microscopy of frozen fracture sections showed favorable compatibility and dispersibility of BPs in TPE-S. In addition, the introduction of BPs showed the most negligible effect on the mechanical properties of TPE-S compared with other flame retardants (aluminum hypophosphite and red phosphorus).