Nanocomposites and conventional flame retardants

For the past several years there was hope that the formation of a nanocomposite alone would permit one to impart fire retardancy to a polymer in all combustion conditions. Flame retardancy is achieved with nanocomposites alone, but not enough for an ignition resistance test such as the limiting oxygen index (LOI) and the UL-94 vertical burning test (ANSI//ASTM D-635/77). 

Cone calorimeter results show a reduction in the combustion rate of nanocomposites with respect to the polymer matrix, while in other tests, such as the UL-94, a self extinguishing behaviour is required to pass the test. The UL-94 test is, indeed, a qualitative pass/fail test performed on a plastic sample (125 x 

With the exeeption of a PA6 nanoeomposite that aehieved a V-0 rating, no other nanoeomposites showed a self-extinguishing behaviour and at least slower burning times are observed for some of the samples. Nowadays it is unclear which measured parameter in the eone ealorimeter experiments controls performance in the UL-94 test. 

The advantage of this approaeh is the possibility to reaeh a desirable flame retardant effeet with a lower amount of halogenated compound. Moreover, the addition of metal oxides, sueh as AO, to halogenated fire retardants increases their effieieney through the formation of antimony trihalide, a volatile product that slows reactions in the flame, even tiiough the oxide itself has no effect. In 

6MMT +H + 6NaCl + Sb203 6MMT +Na + SbClj + SHjO 

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