The last two decades have witnessed a significant growth in using bioderived materials, driven by the necessity of replacing fossil-derived precursors, reducing the fossil fuel consumption, and lowering the global environmental impact. This is possible thanks to the availability of abundant resources from biomasses and the development of optimized technologies based on the principles of sustainability and circular economy. Herein, we report on the synthesis and characterization of new carbohydrate-derived epoxy resins. In particular, 2,5-bis[(oxiran-2-ylmethoxy)methyl]furan has been synthesized and cured with methyl nadic anhydride. The effect of different initiators was studied, in order to identify the most efficient curable formulations. A series of resins was then prepared varying the epoxide−anhydride ratios. The results gathered from physicochemical, mechanical, morphological analyses have demonstrated that the produced furan-based thermosets have the potential to be proposed as sustainable alternatives to the traditional, bisphenol A-containing epoxy resins.

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Epoxy resins are widely used in a variety of application fields, thanks to their good mechanical strength, chemical resistance and adhesion to several substrates. Nowadays, the quite majority of epoxy resins are based on derivatives of bisphenol A (BPA), which poses serious health concerns. This issue is pushing the research towards suitable bio-based alternatives to this product, being furan-based epoxies very promising in this respect. In a previous work, 2,5-bis[(oxiran-2-ylmethoxy)methyl]furan (BOMF) was cured with methyl nadic anhydride (MNA), and successfully used as tinplate coating. Herein, in a view of increasing the sustainability of these epoxy resins, we have replaced MNA with maleic anhydride (MA), which can be derived from vegetable feedstocks, thus obtaining a fully bio-based epoxy resin. This latter has then been used as adhesive for carbon fiber-reinforced thermosetting plastics (CFRP). The curing process of the resin was monitored by differential scanning calorimetry (DSC) and chemo-rheological analysis. The results highlighted the significantly higher reactivity of BOMF towards MA compared to the diglycidyl ether of BPA (DGEBA). The crosslinked samples were characterized in their thermal, mechanical and adhesive properties. In comparison to DGEBA/MA and BOMF/MNA, BOMF/MA showed higher ultimate strain and slightly lower glass transition temperature, tensile modulus and ultimate strength. Interestingly, BOMF/MA displayed outstanding adhesive strength on CFRP joints, outperforming the DGEBA-based counterpart by three times. Indeed, by properly selecting the anhydride curing agent, a highly ductile fully bio-based material was developed for high performance adhesive applications. The overall results demonstrate that the properties of BOMF-based epoxy resins can be tailored to meet technical and safety requirements of downstream applications, representing a sustainable alternative to traditional systems containing DGEBA.

The potential of furan-based epoxy thermosets as a greener alternative to diglycidyl ether of Bisphenol A (DGEBA)-based resins has been demonstrated in recent literature. Therefore, a deep investigation of the curing behaviour of these systems may allow their use for industrial applications. In this work, the curing mechanism of 2,5-bis[(oxiran-2-ylmethoxy)methyl]furan (BOMF) with methyl nadic anhydride (MNA) in the presence of 2-methylimidazole as a catalyst is analyzed. In particular, three systems characterized by different epoxy/anhydride molar ratios are investigated. The curing kinetics are studied through differential scanning calorimetry, both in isothermal and non-isothermal modes. The total heat of reaction of the epoxy resin as well as its activation energy are estimated by the non-isothermal measurements, while the fitting of isothermal data with Kamal’s autocatalytic model provides the kinetic parameters. The results are discussed as a function of the resin composition. The global activation energy for the curing process of BOMF/MNA resins is in the range 72–79 kJ/mol, depending on both the model used and the sample composition; higher values are experienced by the system with balanced stoichiometry. By the fitting of the isothermal analysis, it emerged that the order of reaction is not only dependent on the temperature, but also on the composition, even though the values range between 0.31 and 1.24.