Materials engineering for surface-confined flame retardancy

Polymer materials flammability represents a major limitation to their use and hence to the development of most polymer-based advanced technologies. Environmental and safety concerns are leading to progressive phasing out of versatile and effective halogen-based fire retardants which, so far, ensured a satisfactory polymer fire hazard control. Among the intensive efforts which are being made to develop new, environmentally safe, polymer fire protection approaches, the recognition of the paramount role played by the polymer surface during combustion and the exploitation of the new nanotechnologies developed for polymer surface engineering offer a promising perspective for polymer fire retardance. Indeed, heat transfer to the polymer and diffusion to the gas phase of polymer degradation combustible volatiles, which both fuel the combustion, occur across the polymer surface which characteristics regulate the polymer combustion process. It is shown that by engineering the polymer material surface by intumescent coatings or layer by layer nano-deposition or by oxidic nanostructures sol-gel synthesis, polymer combustion can be conveniently slowed down to extinguishment, complying fire safety rules of specific applications, through the creation of a surface barrier to heat and mass transfer across the polymer surface.