Preparation and characterization of microencapsulated ammonium polyphosphate with polyurethane shell by in situ polymerization and its flame retardance in polyurethane

Microencapsulated ammonium polyphosphate (APP) with polyurethane (MCAPP) was prepared by in situ polymerization of pentaerythtritol (PER) and toluene‐2,4‐diisocyanate (TDI) in the presence of added APP. MCAPP was then incorporated into polyurethane (PU) to obtain flame retarded PU/MCAPP. Fourier transform infrared (FT‐IR) and X‐ray photoelectron spectroscopy (XPS) showed that APP was encapsulated by a layer of PU. It found that the optimal reaction time was 8 hr and microencapsulation led to an improvement in water leaching from scanning electron microscopy (SEM) and determination of water resistance. Thermal degradation of flame retarded PU was also investigated by thermogravimetric analysis (TGA). UL‐94 test and SEM were performed before and after water treatment at 75°C for seven days, and the results showed that PU loading of 30% MCAPP can maintain the V‐0 level, due to the shield effect of microencapsulation.