Furfural-based epoxy thermosets and their glass-fiber-reinforced composites: Performance, aging, and recycling

Global plastic production continues to rise, and the vast majority of these materials are still manufactured from fossil-based feedstocks, contributing to growing concerns regarding environmental sustainability and human health. Conventional fossil derived epoxy systems—particularly those based on diglycidyl ether of bisphenol A (DGEBA)—remain among the most widely used in high performance composite applications. These systems are not only unsustainable but also pose significant environmental and end of life challenges. Glass-fiber reinforced DGEBA composites are extensively utilized in sectors such as wind energy, marine, automotive, and electronics, yet their permanent crosslinked networks hinder recycling and often lead to landfill disposal or downcycling. In response, bio based epoxy thermosets are emerging as sustainable alternatives that offer viable options for feedstock replacement.

This thesis explores furfural derived diepoxy monomers that can be synthesized entirely from renewable feedstocks as potential replacements for DGEBA. Two distinct molecular epoxy resin designs with comparable performance were developed: a "diepoxy ether" resembling conventional DGEBA, and a "diepoxy ester". The ester-based epoxy thermoset additionally enables chemical recyclability through mild base catalyzed methanolysis. Corresponding thermosets and glass fiber composites were fabricated, characterized, and evaluated with respect to their properties, recyclability, and aging behavior. In conclusion, the developed bio-based epoxy systems can match or exceed the performance of fossil-based benchmarks, while offering viable end-of-life pathways for fiber-reinforced composites through closed-loop recyclable ester linkages.