Hemp fabric/epoxy composites manufactured by infusion process: Improvement of fire properties promoted by ammonium polyphosphate

The interest for natural fibers as reinforcement in composites is growing for a large number of products also for aeronautic applications, where the flame retardant requirement is fundamental. In this research, ammonium polyphosphate was incorporated as flame retardant into hemp/epoxy biocomposites produced by infusion technology. Cone calorimeter, vertical burning, dynamic mechanical analysis and bending tests were performed in order to study fire and mechanical behavior of the produced biocomposites with different percentage of ammonium polyphosphate. The results showed a decisive improvement of the flame properties; no-effect on their mechanical properties and on the technological feasibility of the process were observed. Therefore, the addition of ammonium polyphosphate enhanced flame retardancy of hemp/epoxy-resin biocomposites without sacrificing their mechanical properties.