Polyphosphazenes combustion

A major feature of the polyphosphazene skeleton is its ability to resist fire and combustion due to the inorganic elements constitutive of its structure [44,387, 388,459,460]. Moreover, the action of skeletal nitrogen and phosphorus atoms can be enhanced by inserting additional inorganic elements (F, Cl, Br, J, B, metals, etc.) in the substituent groups [459,460]. 

Elastomers. The most advanced applications from a commercial viewpoint are found in the use of polyphosphazenes as elastomers that remain flexible at low temperatures, are resistant to hot oil and hydrauhc fluids, and resist combustion. Polymers with both trifluoroethoxy and heptafluorobutoxy side groups were originally developed for aerospace and automotive applications, but other elastomers that bear both trifluoroethoxy and organosilicon side groups are now... 

A 1980 Naval Research Laboratory report provides data on the toxic combustion products evolved by burning polyphosphazene foams, with and without fire retardants. Toxicants produced were CO, CO2, 2-chlorobutane, 1-chlorobutane, benzene, toluene, and trichloroethylene (for foams not coated with fire-retardant paints) (11). 

Ratings of Some Polyphosphazene and Pol)mrethane Foams," Journal of Combustion Toxicology, 8 282-259 (November... 

The presence of phosphorus in the polymer backbone has a veiy practical consequence, quite apart from the structural issues. Phosphorus is one of the most important elements that prevent the combustion of organic materials. The presence of both phosphorus and nitrogen is synergistic. Thus, the phosphorus-nitrogen backbone in polyphosphazenes ensures that many poly(organophosphazenes) are not only nonflammable but also quench combustion of other compounds with which they are in contact. The mechanism of this fire suppression is believed to be both an interruption of the free radical processes that occur in a flame and the formation of an intumescent char that shields the material from the ingress of oxygen. 

Resistance to combustion is an aspect where nearly all polyphosphazenes are superior to their all-organic counterparts or poly(organosiloxanes). Small molecule phosphorus compounds have long been employed as fire-retardant additives for other... 

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