Phosphazenes as Fire Retardants

A big increase in the number of patent applications on this topic is apparent. The area has been reviewed,177-178 and it is clear that the alkoxycyclophosphazenes find the widest range of applications, particularly in improving the flame resistance of rayon179-188 and polyurethanes.189-191 Phenoxy-substituted phosphazenes have attracted less attention.192-194 Oligomeric chlorocyclophosphazenes also have 

Kajiwara, A. Sakamoto, and H. Saito, Angew. makromol. Chem., 1975,46,63 Chem. Abs., 

Cermak, R. Kopecny, J. Kroupa, J. Kunicky, and A. Novetny, Nehorlavost. Plast. Hurot, Dreva Text., 1974, 85 Chem. Abs., 1975, 83, 80036). 

8 Molecular Structures of Phosphazenes Determined by A-Ray Diffraction Methods  

ClC N CN=PPh3 II V NMe2 Plane containing C—N—P coplanar with triazene ring, P=N 1.622(5) A, C—N—P angle 121° 205 

It is remarkable that the increase in activity in this area noted last year has been sustained, considering that phosphazenes are relatively expensive as fire retardants. Various aspects of this topic have been reviewed, including the concept of N—P synergism in flame retardants. As usual, most interest centres on the propoxy- and aryloxy-cyclophosphazenes and the flame resistance of 

Structure re-examined. P—1.59(2) A L P—N—P 122(1) . Position of benzene in clathrate not defmed exactly because of the tumbling effect 

Ni has square-planar arrangement of bonds. NAtom is co-ordinated to Ni. Non-planar, with long adjacent bonds to P of 1.649,1.635 A. Preparation described in ref. 195 

Bridged at 2,4- rather than 2,6-positions. Ring has crown-saddle conformation 

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