Enhancing Toughness and Flame Retardancy of Epoxy Thermosets Using <scp>SEBS</scp> ‐g‐ <scp>PEG</scp> / <scp>DOPO</scp> Blends

ABSTRACT Enhancing the flame retardancy and toughness of epoxy thermosets without compromising glass transition temperature ( T g ) or mechanical strength is a critical challenge. In this study, the graft copolymer, SEBS‐g‐PEG was prepared by chemically grafting polyethylene glycol (PEG) to the terminal blocks of polystyrene‐block‐poly(ethylene‐ co ‐butylene)‐block‐polystyrene (SEBS). These block copolymers (BCPs) along with various loading levels of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) were covalently incorporated into the epoxy thermosets to enhance their properties. The resulting composites exhibited excellent matrix compatibility, achieving up to a 200% improvement in fracture toughness and a 70% increase in flame retardancy at higher DOPO loadings (e.g., 8 wt%) without plasticizing effects. Notably, T g and tensile strength were preserved, enabling balanced high‐performance composites.