Microencapsulation Technology Derived Flame Retarded Rigid Polyurethane Foam Composite With Superior Mechanical Property and Water Resistance

ABSTRACT Currently, traditional flame‐retardant‐modified rigid polyurethane foam (RPUF) suffers from poor mechanical properties, flame‐retardant migration, and insufficient environmental resistance due to issues in water resistance and compatibility during use. This work employs microencapsulation technology to modify pyrophosphate piperazine (PAPP), successfully preparing polyurethane‐coated flame retardant (PUPAPP), which is then incorporated into the RPUF matrix by a one‐step fully aqueous foaming technique to produce high‐performance RPUF composites. The encapsulation of the PU shell significantly improves the dispersion and compatibility of PAPP in the matrix, resulting in superior mechanical properties of the RPUF/PUPAPP composite compared with the RPUF/PAPP system. Additionally, the migration of PAPP is effectively suppressed, reducing the oxygen index decline rate by 37% after immersion. Furthermore, adding 50 parts of PUPAPP increases the limited oxygen index (LOI) value of the RPUF/PUPAPP composite to 22.9 vol%, achieving UL‐94 V‐0 grade. In addition, the utilization of PUPAPP increases the initial decomposition temperature of the RPUF composite by 32°C, promotes the formation of a dense char layer, and reduces the peak heat release rate by 28.6%. This work provides insights for the development of functionalized flame retardants and high‐performance RPUF composites.