Environmental challenges and perspectives in the development of nanocomposites for enhanced flame-retardant properties

Various types of nanoparticles have been proved their interest as essential components in many flame retardant (FR) systems. Their mechanisms of action with respect to the fire reaction of polymers are diverse, but they often exert a barrier effect, limiting the mass transfer between the residual material and the heat source. They can interestingly be combined with FRs, leading to specific mechanisms of flame retardancy, and for various combinations, synergistic effects can be achieved. The development of emerging FR systems with nanoparticles will be driven by the ability of the industry to upscale possible complex processes of synthesis or modification of these nanoparticles. Beyond fire performance, the economic impact of such processes has to be considered as well as the durability of the materials, regarding aging phenomena and the ability to be reprocessed via recycling procedures. Moreover, emerging FR systems based on new engineering nanoparticles have to prove their lack of toxicological impacts on human health. Life cycle assessments (LCAs) done on polymer nanocomposites indicate that they present nonnegligible environmental impacts, even with “green” polymers as matrices. Complete data on FR nanoparticles are still missing to perform reliable and comprehensive LCAs of any system. Moreover, complex synthesis or modification of nanoparticles may entail elevated consumption of energy and nonrenewable resources.