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The preparation of fire-safe and high-performance carbon fiber reinforced composites with reprocessable resin matrix and recyclable reinforced fibers is of great importance and particularly urgent to solve the current overreliance on petrochemical resources for composite raw materials. Herein, we propose an effective strategy to simultaneously solve the flammability and nonrecyclability of the epoxy resin-based composites, in the form of fire-safe and catalyst-free dynamic transesterification networks by introducing a phosphaphenanthrene-derived diol as a multifunctional modifier for transesterification without using any toxic catalysts. In this strategy, the phosphaphenanthrene moieties enhanced the fire safety; while the hydroxy groups promoted the construction of catalyst-free dynamic transesterification networks. To our delight, the generated epoxy resin and its composite exhibit excellent mechanical properties, high thermal stability, fire safety, fast repairability and malleability. Furthermore, the resin matrix can be dissolved as the low-mass diol molecules participate in bond exchange reactions to achieve CFs with nearly 100% recyclability. [ABSTRACT FROM AUTHOR]

Fire hazard and waste crisis are two challenges for thermosets, particularly for epoxy resins (EPs) possessing the largest market share therein; yet it is beset with difficulties to solve the challenges simultaneously. Herein, a commercialized phosphorus-containing diol named diethyl bis(2-hydroxyethyl)aminomethylphosphonate (DAP) with "trinity" structures containing phosphonate ester, primary hydroxyls and tertiary amine was applied in an epoxy-anhydride curing system to achieve the catalyst-free mixed transesterification within the adaptable carboxylate/phosphonate networks. The phosphonate structure in DAP was covalently bonded into the epoxy vitrimers (EVs), endowing the EVs with intrinsic fire safety. In detail, the peak heat release rate (PHRR), total heat release (THR), total smoke production (TSP) and maximum smoke density (Ds max) values were considerably reduced by 62.0%, 73.6%, 78.9% and 70.8%, respectively. Meanwhile, owing to the self-catalytic tertiary amine and highly reactive primary hydroxyls from DAP, the mixed transesterification within the adaptable carboxylate/phosphonate networks was accelerated, endowing facile reprocessibility and malleability of the vitrimers, which were further degraded into low-mass molecules by simple alcoholysis. Killing two birds with one stone, this work provided a promising and feasible way to make sustainable and fire-safe thermosetting polymers with comprehensive properties. [Display omitted] • Catalyst-free adaptable carboxylate/phosphonate networks were used to construct intrinsically fire-safe epoxy vitrimers. • The vitrimers exhibited observable suppression on heat, smoke and toxic gas during burning. • The vitrimers showed desirable malleability without sacrificing intrinsic fire safety. • Degradation of the vitrimers was achieved via simple alcoholysis, showing multi-path recyclability. [ABSTRACT FROM AUTHOR]

Flame retardancy and recyclability are two important issues in the research field of thermosets, particularly for epoxy resin (EP) with the biggest market share. It is of great importance, but rarely achievable, to integrate these properties simultaneously into EP. Herein, we report a facile way to prepare intrinsically flame-retardant epoxy vitrimers combining rapid recycling and multiple shape memory effects by introducing dynamic ester-linkages with catalytic transesterification activity into the crosslinking networks of EP. The flame-retardant epoxy vitrimers exhibited high T g (∼110.7 °C), desirable thermal stability and excellent flame retardancy with UL-94 V-0 rating, and high LOI of ∼34%. Also, the value of the peak heat release rate (PHRR) and the total heat release (THR) showed 63% and 32% reduction, respectively. Meanwhile, flame-retardant epoxy vitrimers showed high malleability that could be reprocessed in 15 min at 200 °C without sacrificing the mechanical properties and flame retardancy. Moreover, the dynamic transesterification network allowed flame-retardant EP to access multiple shape memory effect. The design of flame-retardant epoxy vitrimers provide a prime example to foster the cyclic utilization of flame-retardant thermosetting polymers. [Display omitted] • A facile strategy was proposed to prepare intrinsically flame-retardant epoxy vitrimers. • The epoxy vitrimers owned high T g , desirable thermal stability and excellent flame retardancy. • The epoxy vitrimers displayed fast recyclability (∼15 min) without loss in flame retardancy and mechanical properties. • The multiple shape memory performance of the epoxy vitrimers was easily manipulated. [ABSTRACT FROM AUTHOR]