Flame‐retardant behavior of a phosphorus/silicon compound on polycarbonate

A phosphorus/silicon flame retardant, MVC‐DOPO, was synthesized from 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) and 2,4,6,8‐tetra‐methyl‐2,4,6,8‐tetra‐vinyl‐cyclo‐tetrasiloxane (MVC) via addition reaction. Its flame‐retardant effect on polycarbonate (PC) was investigated. The phosphorus/silicon flame retardant increased the limited oxygen index and UL‐94 rating and reduced the heat release rate and total heat release of DOPO‐MVC/PC composites during combustion, indicating the excellent flame‐retardant effect of MVC‐DOPO on PC. MVC‐DOPO inhibited the burning intensity of PC material in the gaseous phase and promoted the formation of a more viscous residue in the condensed phase. Through releasing phosphorus‐containing pieces and phenoxy radicals from the phosphaphenanthrene group, MVC‐DOPO quenched the combustion chain reaction in the gaseous phase; through promoting formation of a more viscous residue and a dense char layer from the main actions of the cyclotetrasiloxane group, MVC‐DOPO reduced fuel release and generated a barrier effect in the condensed phase. Hence, MVC‐DOPO effectively exerted a flame‐retardant effect on PC material in both the gaseous and condensed phases during combustion.