Natural fiber reinforced expandable graphite filled composites: Evaluation of the flame retardancy, thermal and mechanical performances

Expandable graphite (EG) weighing 3 wt%, 5 wt% and 7 wt% was incorporated into 20 wt% natural fiber (NF) reinforced epoxy and these composites were characterized using Bunsen burner test, bomb calorimeter, thermogravimetric analysis, dynamic mechanical analysis, combined confocal Raman-Atomic Force Microscope, tensile test, scanning electron microscopy and energy dispersive X-ray method. Two formulations with 3 wt% and 5 wt% EG coating were produced to investigate their flame retardancy in comparison to that of EG filled composites. Increasing EG fillers in the composites significantly improved the fire resistivity and thermal properties, this, however, was found to reduce the mechanical properties. When EG particles were used as intumescent coating, at least 5 wt% content of EG was necessary to provide the sufficient self-extinguishing properties. Chemical treatment of the NFs could considerably enhance the mechanical performances. The morphology of composites, graphite particles and their char were investigated.