A fully degradable epoxy resin based on a nontoxic triphenol derived from diphenolic acid and eugenol

Abstract

The high toxicity of bisphenol A (BPA) is a major concern in the epoxy industry, but the challenge remains in developing bio-based alternatives to BPA that ensure human safety while providing superior mechanical properties and degradability in epoxy resins. In this study, a bio-based triphenol called DPA–EG ester (DEE) is synthesized from diphenolic acid (DPA) and eugenol (EG). Safety assessments for both cytotoxicity and endocrine toxicity demonstrate significantly lower toxic levels than BPA. Compared to the diglycidyl ether of bisphenol A (DGEBA), its epoxide derivative, DEE–EP, exhibits advantages in terms of higher T_g, enhanced toughness, and remarkable degradability in acidic conditions. After being cured with 4,4′-diaminodiphenyl sulfone (DDS), the DEE–EP resin achieved a higher T_g of 181 °C compared to DGEBA, which resulted in a T_g of 168 °C. Additionally, when DEE–EP is cured with succinic anhydride (SA), the resulting resin can be completely degraded under acidic conditions, suggesting great potential for efficient recycling of carbon fiber (CF) fabrics from composites. The unique molecular structure of DEE–EP is responsible for its advantages, as the hydroxyl group forms degradable ester bonds and the three phenyl glycidyl ether structures increase cross-linking density and rigidity in the network. This work presents a promising alternative to BPA, offering low toxicity, high toughness, and excellent degradability, thereby contributing to the development of sustainable bio-based epoxy resins with superior performance.