Abstract
Current evidence shows that while the generation of nanocomposite structures within polymers often leads to significant improvements in fire performance as measured in terms of reduced peak heat release rates, reductions in the ease of ignition and times to extinguishment are not observed. This is particularly the case when nanoparticles such as functionalized montmorillonite clays alone are present in polymers such as polypropylene, polystyrene and polyamides 6 and 6.6. Improvements in flame retardancy have been observed only when nanoparticulate species are present with conventional flame retardant additives. Such combinations may result in either enhanced overall flame retardancy as determined by conventional test methods, such UL94 or LOI, or alternatively a desired level may be achieved at lower than normal levels of conventional flame retardant with accompanying cost savings and matrix property retention.
However, in order to achieve optimal results, the introduction of nanoparticulate species into a polymer matrix must neither reduce its dispersability via degradation of the functionalizing organophilic components nor influence the polymer processability in terms of adversely changing rheological behavior. Given these conditions, commercial exploitation has been achieved principally in the development of ethylene vinyl acetate (EVA)‐based cable sheathings having desired levels of flame retardancy in which significantly reduced levels of the conventional alumina trihydrate retardant are present together with low levels (1‐5%) of dispersed nanoclay. Commercial compounded polypropylene‐based nanocomposites are also available and have been used to produce injection‐molded electrical enclosing media.
While research has been undertaken mainly at experimental levels only, results suggest that combinations of nanodispersed clays and more conventional flame retardants dispersed at the microscale may enable other potential improved flame retardant applications to be realised in the areas of films, fibers, textiles, coatings, foams and composites. However, much of this reviewed work has yielded only indicative results and requires further significant development if the full potential of nanodispersed particulates is to be achieved.