Layer-by-layer assembled flame-retardant architecture toward high-performance carbon fiber composite

Abstract

Fire safety is a permanent challenge in carbon fiber (CF) epoxy resin (EP) composites, which largely restrict their application especially in high-performance fields with flame-retardant demands. Herein, an effective flame-retardant architecture consisting of branched polyethyleneimine (PEI) and ammonium polyphosphate (APP) was successfully fabricated on CFs surface through the facile layer-by-layer (LbL) assembly to achieve a bilayer polyelectrolytes coated CF (BL@CF), which did not only endow excellent flame retardance to the relevant composites (EP/(BL@CF)) with no additional flame retardants, but also maintained desirable mechanical properties. The as-prepared BL@CF were characterized by SEM-EDX, XPS and XRD, indicating that PEI/APP coating was successfully deposited on CFs surface with no damage to the structure of CF. The phosphorus-containing PEI/APP coating imparted high fire safety to the composite, exhibiting a high limiting oxygen index (LOI) value of 41.0%, V-0 rating in UL-94 V test with only 6 deposited bilayers on CFs, and the decrease of peak-heat release rate (PHRR) and total heat release (THR) by 33.5% and 22.5%, respectively, obtained from cone calorimetry. Moreover, thanks to the increased surface roughness and chemical bonds between BL@CF and EP matrix, satisfactory mechanical properties and glass transition temperature of the composite were obtained. Taking these advantages, this facile manufacturing method from layer-by-layer assembly toward superior flame retardance and favorable mechanical properties can bring more chances for advanced composites.