Development of natural fibre reinforced flame retarded epoxy resin composites

Natural hemp fabric reinforced epoxy resin composites were prepared in flame retarded form. Fabrics were treated in three ways: the first method involved the immersion of preheated fabric into cold phosphoric acid solution (allowing penetration into the capillaries of the fibres) and subsequent neutralization, the second way was a reactive modification carried out with an aminosilane-type coupling agent, while the third treatment combined the sol–gel surface coating with the first method. The introduction of phosphorus into the reinforcing fibres decreased the flammability not only of the hemp fabrics, but also of the epoxy composites made thereof. By applying amine-type phosphorus-containing curing agent (TEDAP) in combination with the treated fabrics, V-0 UL-94 rating was achieved. Composites of unexpectedly improved static and dynamic mechanical properties could be prepared only when the simple phosphorous fibre treatment and reactive flame retardancy was combined.