High performance, recyclable and sustainable by design natural polyphenol-based epoxy polyester thermosets

Abstract

Renewable flavonoid and phlorotannin extracts were used as building blocks to synthesize biobased tris-epoxy monomers and further to design and develop sustainable thermosetting resins. The triglycidyl ethers of phloroglucinol and naringenin were combined and crosslinked with a series of anhydrides, four of them being bio-based. The thermosetting resins’ reactivity has been studied, as well as the influence of the chemical structure of anhydride crosslinkers allowing us to obtain highly crosslinked networks with high performance. The designed thermosets show high glass transition values (134–199 °C), high storage moduli at 25 °C (2.7–3.5 GPa), and high crosslinking densities and gel content (>99%). These polyaromatic thermosets are characterized by high mechanical strength and toughness (Young's moduli ∼1.26–1.68 GPa), and they proved to be high heat-resistant materials (LOI ∼28–33%). The sustainability aspect could be related to a particularly important feature of these thermosets, their ability to be chemically recycled by bond exchange reactions. Therefore, the polyaromatic thermosets developed in this study demonstrate important characteristics recommending them as environmentally friendly alternatives to petroleum-based epoxy resins used in various industries such as civil, automotive, marine, aerospace, and space.