Fecha de publicación: -- Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE A lanthanum-assisted core–shell intumescent flame retardant integrates acid, gas, carbon, and catalytic functions within a single particle. At 15 wt% loading, polypropylene achieves UL-94 V-0 performance and retains this rating after 72 h water immersion, while markedly reducing heat release and maintaining tensile strength through enhanced interfacial compatibility and condensed-phase char protection.

ABSTRACT
Polypropylene (PP) is widely used in polymer products, but its high flammability and the poor resistance to water exposure of ammonium polyphosphate (APP)-based flame-retardant systems limit broader applications. Herein, a lanthanum-assisted core–shell flame retardant (LAPP@M) was fabricated by La3+ modification of APP followed by microencapsulation with an HDI-cross-linked β-cyclodextrin shell. The hybrid structure integrates acid source, gas source, bio-based carbon source, and catalytic functionality within one particle. Structural analyses confirmed the formation of a La-modified APP core and organic shell, which changed the particle surface from hydrophilic to hydrophobic. With only 15 wt% LAPP@M, PP achieved a UL-94 V-0 rating and an LOI of 29.5%, and retained the V-0 rating after 72 h of static water immersion, demonstrating improved short-term resistance of the flame-retardant performance to water exposure. Cone calorimetry showed that the peak heat release rate and total heat release were reduced by 75.2% and 26.3%, respectively, relative to neat PP. Char analysis, Raman spectroscopy, TG-FTIR, and TGA revealed that La promoted condensed-phase charring, while the β-cyclodextrin shell improved water resistance, interfacial compatibility, and char formation. This work provides an effective particle-engineering strategy for flame-retardant PP composites with improved resistance to short-term water exposure.