Bio-sourced alternatives to diglycidyl ether of bisphenol A in epoxy–amine thermosets

Since the 1940s, bisphenol A (BPA) has been used in the plastic industry, reaching production of 10 Mt in 2022. More than 30% of the produced BPA is used in the production of epoxy resins. Decades of research has now provided enough evidence that BPA has endocrine-disrupting activity. Hence, it is an urgent matter to replace BPA in the production of epoxy resins. In the past years, considerable efforts have been put into finding alternatives to the toxic BPA. However, not only does the diglycidyl ether of BPA exhibit high polymerization reactivity, but also the presence of aromatic rings confers interesting thermomechanical resistance to epoxy networks therefrom. Hence, these properties are also expected from potential alternatives to BPA. In this review, first, the elements leading to toxicity of BPA are explained and then thorough accounts of possible bio-sourced aromatic alternatives to BPA are gathered. The reported synthetic routes for each of these alternatives and their toxicity are described. Also, their use in synthesis of epoxy resins and how the new alternatives influence the mechanical properties are discussed. This is a concise summary of the structure–property and structure–toxicity relationship for possible bio-sourced substitutes of BPA in synthesis of epoxy resins.