Construction of 2D/1D Hybrids through Hyperbranched Polyphosphoramide toward Improving Mechanical and Flame-Retarding Properties of Epoxy Composites

It is a great challenge to achieve good flame retardancy with no mechanical deterioration for polymeric composites and further amplify their application. Herein, carbon nanotubes@hyperbranched polyphosphoramide@MoS 2 (CNT@HBPPA@MoS 2 ) hybrids were facilely fabricated by connecting one-dimensional (1D) CNT and two-dimensional (2D) MoS 2 with hyperbranched polyphosphoramide (HBPPA) via in situ polymerization. The hybrids exhibited a low maximum mass loss rate (0.83%/min) and a high char yield (78.6 wt %) at 700 °C. The incorporation of 4% hybrids endowed the relating epoxy (EP) composite with the best flame retardancy (LOI of 30.5% and UL-94 rating of V-1) and the lowest fire risk (decreased peak heat release rate (PHRR) of 49.1%, total smoke product (TSP) of 29.5%, and CO yield (COY) of 29.2%). The gas- and condensed-phase analysis revealed cooperative flame retardant mechanisms including fuel diluting effect, reinforced barrier effect, and catalytic and intumescent charring function. Meanwhile, the tensile strength, elongation at break, and impact strength of the above EP composites increased by 34.6, 11.9, and 5.9%, respectively. Thus, the simultaneous enhancement in both fire safety and mechanical properties of EP composites was successfully achieved by facile hybridization of 1D/2D nanomaterials through reactive hyperbranched polymers, which provides valuable inspiration for developing high-performance polymeric composites.