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

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/PSi₂) 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/PSi₂ 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.