Biomacromolecules and bio-sourced products as flame retardants for textiles: a novel approach toward sustainability.

It is well-known that textiles, if not intrinsically flame retarded, burn vigorously and quickly when exposed to a flame or an irradiative heat source: starting from the 1950s, this detrimental behavior has been overcome by designing suitable and efficient chemical products, i.e. the so-called flame retardants”. These materials, thanks to their structure and chemical compositions, are capable to slow down or even stop the combustion processes, actively working according to different reaction mechanisms occurring in the condensed and/or gas phase surrounding the burning textile substrate. Despite their high efficiency and wide availability on the market, some toxicity issues and the need to utilize low environmental impact alternatives have pushed and are still pushing the academic and industrial community towards the design of new products. In this context, the suitability of selected biomacromolecules (such as nucleic acids and proteins) and bio-sourced products (i.e. phytic acid, tannins and chitosan, among a few to mention), possibly recovered from wastes, crops and byproducts, has started to be thoroughly investigated. In particular, it was found that these “green” products, which typically contain some key flame retardant elements (such as phosphorus, nitrogen, and sulphur), can be effortlessly applied to textiles using standard impregnation/exhaustion procedures or even advanced methods, like the layer-by-layer (LbL) technique. Furthermore, this new class of flame retardants is mainly responsible for the development of a stable protective carbonaceous residue on the burning textile, as a result to the application of a heat flux or a flame, hence showing high activity in condensed phase. Their first flame retardant use in the textile world dates back to 2013, when a whey protein waterborne coating was, for the first time, successfully applied to cotton: from that time, a significantly increasing number of articles appeared in the scientific literature. This book chapter is aimed at summarizing the progress and the recent advances related to the use of biomacromolecules/bio-sourced products as efficient flame retardants for different fabrics, either natural or synthetic. Besides, the current limitations concerning this specific utilization and some possible future developments will be elucidated.