FIRE RETARDANCY OF TEXTILES THROUGH SURFACE ENGINEERING METHODS: RECENT ADVANCES

Flame retardants (FRs) for textiles have undergone and still undergo a significant evolution toward the fulfillment of the recent EU and USA directives that are imposing the use of low impact, high sustainable products, as well as the seeking for very efficient, low cost systems that could replace halogenated chemicals at an industrial scale. In this context, new phosphorus and nitrogen flame retardants have been synthesized, demonstrating their availability as suitable FR products for both natural and synthetic fibers/fabrics. In parallel, the strong development of nanomaterials and nanotechnology has opened new pathways for successfully exploiting their nano-size in order to achieve outstanding thermal, mechanical, electrical, barrier, …, features in the designed nanocomposite structures, which the nanomaterials have been embedded in. Among the different potential combinations of nanostructures with flame retardants products possessing environmentally-friendly features, some surface engineering methods have been designed at a lab scale, showing a good potential and in some cases the possibility of up-scaling at least at pre-industrial level. In particular, the use of Layer by Layer nanoarchitectures and of sol-gel derived nanoparticles and nanocoatings for conferring flame retardant features to different types of fabrics has been thoroughly investigated. Although the setup of these two surface engineering methods is quite different, their common peculiarity refers to the possibility of locating the flame retardant “product” specifically on the textile surface, where it is primarily needed: indeed, the surface is the place where the degradation of the polymer starts to occur, as a consequence of the exposure to a heat flux or of a flame application. Therefore, the proposed surface engineering approaches can effectively limit or stop the fire propagation, avoiding, at the same time, an overcharge of the FR additive within the polymer substrate and without changing the bulk properties of this latter. The present work is aimed at summarizing the recent attempts for conferring fire retardant features to both natural and synthetic fabrics (namely, cotton, polyester and their blends), trying to exploit the aforementioned surface engineering approaches at a lab scale. More specifically, an overall view of the Layer by Layer and of sol-gel methods will be given; then, some examples of flame retarded textiles will be described. In addition, some of the potentialities associated with the use of suitable biomacromolecules (namely proteins and nucleic acids) as novel low-environmental impact flame retardant additives in surface engineering methods will be presented. Finally, the current limitations of the proposed surface engineering technologies will be briefly summarized.