Epoxy polymer using tannic acid as the green crosslinker, exhibiting globally enhanced mechanical, insulating and thermally conductive properties

Epoxy resin polymers are characteristic of outstanding mechanical and insulating performances, establishing them as critical insulating components in modern electronic devices and power systems. Bio-based polyphenol organics, a substitute for petroleum-based anhydride to cure epoxy resins, can restrict the waste of non-recyclable petroleum resources, meeting the current demand for sustainable development. However, due to rapidly developing industrial demands, such epoxy polymers using bio-based organics as curing agents need further exploration to realize excellent comprehensive properties. Herein, epoxy resin with significantly high crosslink density and few intermolecular defects has been successfully prepared using 1,4-butanediol diglycidyl ether-modified tannic acid as the green crosslinker. The most outstanding comprehensive properties have been realized by adjusting the mass ratio of 1,4-butanediol diglycidyl ether to bisphenol-A epoxy resin to 3: 10. Specifically, the tensile strength, elongation at break, breakdown strength and intrinsic thermal conductivity of tannic acid cross-linked epoxy resin reached 67.6 MPa, 5.4%, 29.8 kV/mm and 0.59 W/(m·K), respectively, globally higher compared with epoxy/anhydride system, which is attributed to the tighter molecular structure, fewer molecular entanglements and less internal defects. Therefore, this work provides a simple and feasible method for preparing tannic acid cross-linked epoxy resin polymers with excellent comprehensive properties, offering potential application value.