Epoxy resin composites reinforced and fire-retarded by surficially-treated carbon fibers via a tunable and facile process

Construction of carbon fiber (CF)-reinforced epoxy resin (EP) composites with excellent mechanical properties and desired flame retardancy is of particular interests for both academia and industry. In this work, an interfacial treatment strategy is used to address the above issues instead of adding flame retardants into the composites: without additional other flame retardants, EP is fire-retarded and reinforced only by surficially-treated CFs, which are fabricated by quickly soaking CFs in aqueous solution of polyelectrolyte complexes (PEC) consisting of polyethyleneimine (PEI) and ammonium polyphosphate (APP) at room temperature. Both the content and the morphology of the resulting PEC coating are conveniently tuned by adjusting the coating conditions. Without any change in the molding process of the EP/CF composites compared with the conventional process, the phosphorus-containing PEC coating of CF surfaces endows the EP/CF composites with high fire retardancy, exhibiting a high limiting oxygen index of 43%, UL-94 V-0 rating, and a 47% reduction in the peak heat release rate (PHRR) from cone calorimetry tests. Moreover, the PEC coating greatly improved the interaction between CFs and EP matrix, and enhanced the mechanical properties and glass transition temperature of the composite. Therefore, this work presents an effective and facile strategy to develop fiber-reinforced composites with superior fire-retardant and mechanical properties for future massive production.