Carboxyl group containing aqueous-based polyurethane (PU) is prepared by a conventional method. PU carboxyl group is the reactive site toward an aziridinyl containing post-curing agent for PU curing system. Two compounds are prepared from the substitutions of phosphorus oxychloride with aziridine (TAP) or then with N, N-diethylamine (DDP), respectively. TAP or DDP consists of three or two aziridinyl groups and also contains stable phosphorus-nitrogen bonds. It serves as a post-curing agent and a reactive flame retardant for the aqueous-based PU simultaneously. The mechanical and the physical properties of post-cured PU are modified corresponding to the curing dosage. The thermal stability of the resulted PU is improved and confirmed by thermogravimetric analyzer and dynamic mechanical thermal analyzer. Furthermore, the combustion behaviors of final PU are evaluated by the measurements of limiting oxygen index and cone calorimeter.
Polymer Degradation and Stability 65(3), pp.359-371