Enhanced Flame retardancy of flax-biocomposites for the construction market

Biocomposites are made of natural fibers which are an attractive alternative to conventional synthetic fibers such as glass or carbon fibers not only because their intrinsic properties but also because their contribution to more sustainable materials. However, natural fibres are flammable and the biocomposites need to be protected against fire for safety reasons but also to meet the strictest EU regulations of the transport and construction sectors.  Thermosetting composites need high loadings of flame retardant additives to achieve satisfactory results in terms of flammability.  However, high levels of flame retardants lead to significant deterioration in mechanical properties. This work explores the possibility of reducing the flammability of flax-biopolyester composites with potential uses in transport and construction sectors through the combination of several novel fire retardant additives which are halogen free and are considered environmentally friendly. Cone calorimeter tests indicate that proper combinations of FR additives reduced HRR and MARHE values up to a 60% delaying the ignition time with respect to the unfilled material. These results were achieved at concentrations much lower than with traditional solutions. However the addition of dimethyl propyl phosphonate (PMPP) to the resin formulation with ATH and APP failed to demonstrate any significant synergistic effect at reducing the HRR