Enhanced flame retardancy and smoke suppression of thermoplastic polyurethane membrane via “two-phase” synergistic effect

Abstract

The design and development of thermoplastic polyurethane (TPU) membranes with both flame retardancy and smoke suppressing properties has become a hot and difficult research topic. In this work, a novel TPU membrane with enhanced flame retardancy and smoke suppression (PL-D-G-TPU) was constructed by electrospinning technology using phytic anhydride (PL), daidzein (D) and graphite (G). The resulting composite fibers of PL-D-G-TPU exhibited a smooth surface and uniform pore size distribution. It was worth noting that the peak heat release rate and total smoke release of PL-D-G-TPU were 54 kW/m² and 0.32 m², respectively, which reduced by 65.82 % and 33.33 % compared with TPU, meeting the requirements of refractory materials. This is due to the synergistic catalytic effect between phosphoric acid or polyphosphate derived from PL and graphite resulted in the generation of a significant amount of dense and stable residual carbon in the matrix. It hindered the transfer of oxygen, toxic smoke and heat, which retarded the degree of combustion and the release of smoke. Additionally, daidzein released H• and quenched gas phase oxygen-containing free radicals to promote the cycle regeneration of PO• during the decomposition of PL, which jointly inhibited combustion. Subsequently, its potential effects in packaging and textile industries were discussed to expand application fields. Therefore, this work presents a simple, green and innovative strategy to simultaneously improve the flame retardancy and smoke suppressing properties of TPU membranes, thereby expanding their potential industrial applications.