Novel organophosphonate-decorated WS2 nanosheets towards flame retardancy and mechanical enhancement of epoxy resin

By noncovalently surface-modifying 2D WS 2 nanosheets (WC) with in situ generated iron ethylenediamine tetramethylene phosphonate (FeP), novel organophosphonate-decorated nanosheets (WC@FeP) were designed and prepared. Combining the physical barrier effects of WC nanosheets with the catalytic charring activity of FeP, WC@FeP improved the flame retardancy of the epoxy resin (EP), including heat inhibition and smoke suppression. Compared with those of neat EP, the EP composites containing 8 wt% of the WC@FeP (EP/8WC@FeP) passed a UL94 V-0 rating with a LOI value increased from 22.5 to 29.5 vol%. Furthermore, the peak heat release rate (PHRR), total heat release rate (THR), and total smoke release (TSP) of EP/8WC@FeP were remarkably reduced by 58.2%, 25.1%, and 44.5%, respectively. In addition, thanks to the large aspect ratio of the decorated nanosheets with flexible-but-tough nature, WC@FeP effectively enhanced the mechanical properties of the composites, in which the tensile strength and modulus of EP/8WC@FeP were enhanced by 23% and 24%, respectively, without sacrificing the toughness. Taking advantage of these features, the surface organo-decoration of 2D nanosheets broadens their applications in polymeric materials.