Nanoclay Based Flame Retardant

This is another important and widely used polymer. Nanocomposites have been prepared based on this rubber mostly for flame-retardancy behavior. Blends with acrylic functional polymer and maleic anhydride-grafted ethylene vinyl acetate (EVA) have also been used both with nanoclays and carbon nanotubes to prepare nanocomposites [65-69]. 

In case of other fillers, the nanofillers can introduce new functionality into the polymer, e.g. electrical conductivity in case of carbon based nanoparticles, barrier properties in case of platelet like nanofillers (nanoclay, expanded graphite), enhancement of mechanical properties, enhanced flame retardancy, and many others. 

Belgian cable company Kabelwerk Eupen has introduced a commercial application for polymer-clay composites to make flame retardant cables. EVA-based cable jackets are combined with the clay materials in what is called a one-pot synthesis extrusion technique. 5% of the nanoclay improves the fire performance of the EVA compound by promoting char formation and delaying degradation. In addition, it prevents dripping of any burning polymer material. 

In the USA the National Institute of Science and Technology has discovered that the dispersion of a very small quantity of carbon nanotubes into PP greatly reduces the flammability of the polymer. An alternative approach to flame resistance is offered by the US PolyOne Corporation which supplies a range of nanoclay-based additives. These Nanoblend additives are claimed to be able to boost the fire resistance of flame-retardant PE and PP. 

Intumescence also has a role in the flame retardancy of textiles7 Recently, Horrocks et al. investigated the inclusion of nanoparticles in combination with intumescent flame retardants in polyamide-6 and polyamide-6,67 They suggest that the incorporation of nanoclay does not necessarily increase the LOI value when evaluated as film samples, but they showed the benefit of using nanoclay in polyamides when combined with APP-based formulations. The efficiency is increased by an average factor of 2. 

Although there have been other attempts to produce nanoclays in the presence of flame retardants in other fiber-forming polymers, such as polypropylene and poly ester,their combined effects in fibers have not been directly observed. In the case of polypropylene, the addition of nanoclay to a flame retardant formulation based on a hindered amine stabilizer and a char-promoting ammonium polyphosphate at concentrations on the order of only about 5% w/w does enhance char... 

---