Construction of a core-shell structure compound: Ammonium polyphosphate wrapped by rare earth compound to achieve superior smoke and toxic gases suppression for flame retardant flexible polyurethane foam composites

To expand the application and the added value of rare earth compounds, it was utilized to enhance fire safety of flexible polyurethane foam (FPUF) in furniture field. La2Sn2O7 with pyrochlore structure was utilized to wrap ammonium polyphosphate (APP), forming a novel core-shell structure compound (LAPP) and used in FPUF. Compared to pure FPUF, the peak of heat release (PHRR) and peak of smoke production rate (PSPR) of FPUF composites were reduced by 37.5% and 33.3%, respectively. Moreover, the released toxic gases (such as, CO, CO2, NO and NO2) during combustion were dramatically decreased. This is due to the LAPP not only exerted the combustion catalysis toxic gases and smoke reduction effect, but also enhanced the char residue with high quality and quantity. Therefore, to make full use of China's rare earth resources, it provides a facile and effective strategy to fabricate polymer composites with high fire safety for the furniture field.