Preparation of a novel phosphorus–nitrogen flame retardant and its effects on the flame retardancy and physical properties of polyketone

In this study, a novel phosphorus–nitrogen flame retardant (PNFR) was synthesized, and its flame retardancy for polyketone (PK) was systematically investigated. The chemical structure of PNFR was characterized using NMR spectroscopy. The PNFR was considered to generate phosphoric acid, which catalyzed the char formation reaction of PK via condensed‐phase decomposition. When 7 wt% PNFR was incorporated into PK, the limiting oxygen index value was increased from 20.2 to 25.9%. In addition, this PK‐PNFR sample achieved the rating of VTM‐0 because it exhibited self‐extinguishable properties and did not drip when fire was removed from it. As the PNFR content increased, while the initial decomposition temperature decreased, the amount of residual char considerably increased. Thus, the PNFR was thought to impart flame‐retarding ability to PK via superior condensed‐phase mechanism. Additionally, the decrease in melting temperature and enthalpy of fusion was observed after the addition of PNFR, which implied that the PNFR could act as plasticizer for PK.