High-performance epoxy resin with flame-retardant, transparent, and ultraviolet shielding properties based on a vanillin-based multifunctional macromolecule.

Flame-retardant epoxy resins with tough, transparent, ultraviolet shielding, and low dielectric properties have fascinating prospects in electronic and electrical applications, but it is still challenging at present. In this work, a bio-based macromolecule was synthesized from vanillin (a lignin derivative), phenyl dichlorophosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO), and poly(propylene glycol) bis(2-aminopropyl ether). The bio-based macromolecule, namely, MFR, was designed and added to the epoxy resin (EP). The cured EP containing 15 wt% MFR (i.e., EP/MFR15) exhibits excellent flame retardancy with an Underwriter Laboratory 94 (UL-94) V-0 rating and a limiting oxygen index (LOI) of 29.2 %. Furthermore, the peak heat release rate (PHRR) and total heat release rate (THR) are drastically reduced by 59.5 % and 40.7 %, respectively. Meanwhile, EP/MFR15 shows 20.3 % and 43.8 % improvements in tensile strength and toughness, respectively. Moreover, MFR simultaneously endows EP with accessional ultraviolet shielding performance and low dielectric constant without sacrificing transparency. This work provides a promising strategy for fabricating a bio-based macromolecular flame retardant and preparing a high-performance EP composite with versatile properties.