Flame retarding and reinforcing modification of ramie/polybenzoxazine composites by surface treatment of ramie fabric

Ramie fabrics were firstly treated with amino functional silane coupling agent. Then the layer-by-layer self-assemble technique was used to develop flame retardant coating on flexible and porous ramie fabrics through the electronegativity of ammonium polyphosphate (APP) and the electropositivity of polyethyleneimine (PEI). The content of the coating was measured to be 13.8 wt.%. The flame retardant ramie/polybenzoxazine composites were prepared with APP/PEI treated ramie fabrics as reinforcement. The self-assembly of the flame retardant coating on the fabric surface endowed the composites with self-extinguishing ability, and the treated composites can reach UL-94 V-0 rating during the vertical flame tests. Moreover, the interfacial adhesion of the treated composites has been enhanced. In consequence, its tensile and flexural properties have been improved and the treated composites show much higher strength and toughness compared with the untreated composites.