Enhanced flame retardancy and thermal stability in flexible polyurethane foam through synergistic core-shell structured DBDPE@PMA particles

Abstract

This research presents the synthesis of core–shell structured flame retardant particles, DBDPE@PMA, which combines the flame-retardant and toughening functions. These particles utilize decabromodiphenyl ethane (DBDPE) as the core and a copolymer of methyl methacrylate and acrylic acid (MMA-AA) as the shell, which are created via emulsion polymerization. The process involved an initial reaction of DBDPE@PMA with isocyanate, followed by foaming with polyether polyol to fabricate flame retardant, and the flexible polyurethane foam (P/D-FPUF) was thermally insulated. The study examined the influence of DBDPE@PMA on the flame retardancy properties of flexible polyurethane foam. Scanning electron microscopy confirmed the encapsulation of DBDPE by the polymer, resulting in a core–shell composite particle. The interaction between the carboxylic groups (–COOH) on the DBDPE@PMA shell and isocyanate enhanced the interfacial bonding, thereby increasing the foam's apparent density and ensuring better integration with the polyurethane matrix. However, DBDPE@PMA had aggregates on the foam matrix bubble holes, resulting in uneven bubble holes. DBDPE@PMA markedly improved the flame retardancy and thermal stability of the foam, compared to both pure polyurethane and foam containing solely DBDPE (10D-FPUF). The oxygen index value of the foam with 20% DBDPE@PMA (20P/D-FPUF) reached 33.6%, with UL-94 horizontal and Vertical burning level tests achieving the highest classifications. The char residue after thermal degradation increased significantly from 1.93% in pure foam to 5.06%. While the smoke density level rose, the duration to peak smoke density was prolonged to 78 s, offering an enhanced margin for evacuation during the initial stages of a fire.

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