Flame Retardancy Properties of Clay–Polymer Nanocomposites
Résumé
The majority of this chapter on nanocomposites and flame retardancy is related to layered silicates or phyllosilicates, usually called clays. The clay family is very varied, but the scientific literature on polymer nanocomposites concerns mainly 2:1 silicates, particularly the family of smectites, and predominantly organomodified montmorillonites. From the pioneering work of NIST and Cornell University in the 1990s, many studies have been performed on these materials, as with other kinds of nanoparticles, to highlight their potential as flame retardants. A lot of work has been performed on the development of surface and interfacial modifications of clays to disperse them in polymers to achieve nanostructures. This led to investigations into the processing of clay nanocomposites to improve their reaction to fire. Research work has also been carried out on the understanding of the mechanisms of the fire-retardant action of organomodified layered silicates regarding surface modifications and interactions with other possible components used to improve the fire retardancy of polymers. Moreover, in relation to investigations concerning mechanisms, the research into synergistic effects in multicomponent systems represents a significant part of the literature devoted to clays and flame retardancy. This last topic is particularly important for companies since they have tried to replace halogenated compounds in many applications, such as in cables or in the transportation area. In fact, since the incorporation of clays, even organomodified does not meet fire standards such as vertical UL 94 V at the level V0 for thin specimens, therefore a large panel of combinations was investigated, leading in some cases to very complex compositions.