Phosphazene compounds are a class of compounds with P and N as the basic skeleton, and there is a good synergy between the two elements. Alfa Chemistry provides you with environmentally friendly phosphazene flame retardants, including inorganic phosphazene compounds and organic polyphosphazene flame retardants.
Mainly include cyclotriphosphazenes, such as hexachlorocyclotriphosphazene, hexaphenoxy cyclotriphosphazene, etc.
Mainly include linear polyphosphazenes and cyclic cross-linked polyphosphazenes. Currently, polyphosphazene has not been commercialized, and Alfa Chemistry provides custom synthesis services.
The flame retardant mechanism of phosphazene compound flame retardants (PFRs) is the comprehensive effect of multiple pathways.
PFRs absorb heat during thermal decomposition.
PFRs can be thermally decomposed to generate phosphoric acid, metaphosphoric acid and polyphosphoric acid, which form a non-volatile protective film on the surface of the polymer material to isolate the air.
PFRs releases carbon dioxide, ammonia, nitrogen, water vapor and other gases after heating, diluting oxygen, so as to achieve flame retardant synergy.
PO· groups are formed during combustion, which can combine with H·, HO· active groups to inhibit the flame.
The general schematic diagram of flame retardant mechanism of polyphosphazenes 
Microencapsulated Phosphazene Flame Retardant
Lijie Qu et al. developed a phosphorus-nitrogen-silicon synergistic flame retardant Si(H) microcapsule system for improving the flame retardancy of epoxy resins (EP). In this work, the microcapsule flame retardant takes silica as the shell, hexaphenoxycyclotriphosphazene as the core, and forms a cross-linked network with EP, thus realizing the ideal of low addition amount and high flame retardancy performance. 
Formation of Si(H) microcapsules and cross-linked network of EP composites 
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