Thermal degradation and flame retardancy of microencapsulated ammonium polyphosphate in rigid polyurethane foam

Microencapsulated ammonium polyphosphate MFAPP or VMFAPP with shell of melamine–formaldehyde or poly (vinyl alcohol)–melamine–formaldehyde resin was prepared by in situ polymerization, respectively. The flame-retardant performance of rigid polyurethane foam (PU) containing MFAPP or VMFAPP was analyzed by limiting oxygen index and UL-94 test. Thermal degradation behaviors of PUAPP, PUMFAPP and PUVMFAPP were studied using TG and TG–FTIR. Above results indicated that VMFAPP and MFAPP have better water resistance and flame retardancy compared with ammonium polyphosphate (APP) in PU composites. Flame-retardant properties of PUMFAPP and PUVMFAPP composites were rarely changed after hot water treatment. Due to better compatibility and the presence of active groups on the surface of APP, microencapsulation demonstrated a positive effect on the mechanical property of PU composites.