Facile Synthesis of a Bio‐Based Macromolecule Endowing Epoxy Resin With Charming Flame‐Retardant, Transparent, and Ultraviolet Shielding Properties

ABSTRACT Developing epoxy resin (EP) with satisfactory comprehensive properties has significant prospects in high‐tech industries, but achieving this goal remains a significant challenge. In this work, a macromolecular flame retardant (PSi) was synthesized using vanillin, phenylphosphonic dichloride (PPDC), 9,10‐dihydro‐9‐oxa‐10‐phospha‐phenanthrene 10‐oxide (DOPO), and 1,3‐bis(aminopropyl)tetramethyldisiloxane (DAPTMS). PSi was subsequently utilized to fabricate high‐performance EP. The EP with 2 wt% PSi (i.e., EP/PSi 2 ) exhibits satisfactory flame‐retardant performance. It achieves a V‐0 rating in the Underwriters Laboratories‐94 (UL‐94) test with a limiting oxygen index (LOI) of 29.2%. The peak heat release rate (PHRR) and total heat release (THR) decreased by ~14.7% and ~9.6%, respectively. Compared to the unmodified EP, the tensile strength and impact strength of EP/PSi 2 increase by ~9.0% and ~67.5%, respectively, while maintaining a high glass transition temperature ( T g ). Moreover, the incorporation of PSi significantly enhances the UV‐shielding properties of EP without sacrificing its transparency. This work provides an integrated strategy for developing an efficient vanillin‐based flame retardant. The fabricated flame‐retardant EP exhibits mechanical robustness, transparency, and UV‐shielding properties with significant prospects for broad industrial applications.