Recent advances in carbon-based nanomaterials for flame retardant polymers and composites

Abstract An urgent need is to reduce the flammability of polymers and manage their toxic thermal decomposition products. Although conventional halogenated, metallic and phosphorus-based flame retardants (FRs) proved effective, they are known to cause major damage to human health and the environment. Containing carbon nanomaterials as new flame retarding additives, polymer nanocomposites have displayed high flame retardance, mechanical performance and electrical and thermal conductivity – a feat unmatched by conventional FRs. In this article we review very recent advances in carbon nanomaterials as FRs for polymers and composites as well as new understanding of the underpinning flame retarding mechanisms. Carbon nanomaterials, i.e. graphene, carbon nanotubes and carbon black are discussed as alternatives to conventional fillers for their effectiveness in improving the polymers' flammability, mechanical properties and conductivity. The synergy between carbon-based nanofillers and conventional FRs is comprehensively reviewed, concluding that adding small fractions of carbon nanomaterials with conventional FRs into polymers can synergistically improve flame retardancy resulting multifunctionalities such as thermal and electrical conductivity, without compromising the polymers’ mechanical performance. Combining carbon nanomaterials, chemically or physically, with other compounds or nanoadditives containing P and N elements can create significant synergies and thus opportunities to develop multifunctional polymers and composites with superior flame-retardant properties.