The Flame‐Retardant System Composed of Silane‐Modified DOPO and Melamine Towards Enhancing Flame Retardancy, Thermal, and Mechanical Properties of Rigid Polyurethane Foam

ABSTRACT A DOPO modified with a silane coupling agent (DOPO‐Si) was prepared, and combined with melamine (MA) to form a flame‐retardant system, which was added to rigid polyurethane foam (RPUF) to enhance its flame‐retardant, thermal, and mechanical properties. This study aimed to develop a new flame‐retardant system that can not only ensure flame‐retardant efficiency but also improve mechanical properties due to its good dispersibility. After introducing the flame‐retardant system into the RPUF, the thermogravimetric analysis results showed that the initial decomposition temperature of RPUF‐4 increased by 3.72%, and the activation energy increased by 42.5 kJ/mol. Compared with pure RPUF, the peak heat release rate (PHRR) and total heat release (THR) of RPUF‐4 decrease by 28.53% and 18.54%, respectively. The limiting oxygen index (LOI) reaches 24.50%, meeting the UL‐94 V‐1 rating. Due to the good compatibility between DOPO‐Si and the RPUF, the compressive strength and energy absorption efficiency of the modified RPUF were both improved. This study highlighted the excellent dispersibility and synergistic flame‐retardant efficiency of DOPO‐Si and MA, providing new possibilities for the application of new flame‐retardant systems.