Bio-based epoxy resin composites reinforced with surface-modified cellulose fabrics: Coupled enhancement of flame...

Cellulose-based cotton fabrics (COF) offer great potential for reinforcing sustainable resin matrix composites, but their intrinsic flammability limits practical applications. In this study, an effective flame-retardant coating composed of 3-aminopropyl triethoxysilane (APTES), oxidized carbon nanohorns (oSWCNHs), and ammonium polyphosphate (APP) was successfully fabricated on the surface of cotton fabrics via a facile layer-by-layer (LBL) assembly. The surface modification effectively regulated the interfacial interactions of cellulose by introducing hydrogen bonding and ionic interactions. Bio-based epoxy composites reinforced with the modified cellulose fabrics exhibited remarkable fire resistance, with the composite containing four bilayers of APTES/oSWCNHs/APP (EP/MF@4BL) achieving a limiting oxygen index (LOI) value of 29.3 ± 0.2 % and a V-0 rating in the UL-94 V test. Cone calorimeter tests revealed that, compared with neat epoxy resin, EP/MF@4BL showed notable decreases in pHRR (-42 %), THR (-53 %), TSP (-56 %), and back-surface temperature (-69 %), confirming the synergistic improvement in flame retardancy and thermal insulation. Mechanically, the incorporation of APTES and oSWCNHs enhanced the internal compatibility of the composites, as evidenced by increased short-beam strength and shear modulus. A customized setup was further employed to study the coupled mechanism between flame retardancy and mechanical behavior under simultaneous tensile loading and heat exposure, revealing that the coating acts as both a thermal barrier and structural stabilizer. This work presents a sustainable strategy for developing natural cellulose-reinforced bio-based composites with coupled enhancement in fire safety and mechanical performance.