Highly Bio-Based Photo-Curable Resin Comprising Itaconic Acid and Isosorbide Enhanced by Diethyl Itaconate Suitable for Additive Manufacturing

Abstract Commercial resins used for stereolithography additive manufacturing generally comprise acrylic/methacrylic photo-polymerizable systems, which often pose health concerns, environmental impacts, and unsustainable structural characteristics. This work aims to synthesize an entirely bio-based, photo-curable precursor using itaconic acid as a sustainable alternative to the commonly used free-radical polymerization precursors for additive manufacturing. Two main components, the resin diisosorbide itaconate (DII) and the reactive diluent diethyl itaconate (DEI), were successfully synthesized via Fischer esterification and structurally confirmed by FTIR and 1H NMR. We assembled four systems in total: DII with 0%, 15%, 30%, and 45% DEI to investigate the functional properties of the precursor mixtures. We investigated the rheological profile and photo-curing activity by viscometry and photo-DSC to verify suitability for processing via stereolithography. We successfully prepared photocured specimens to investigate thermo-mechanical properties via DMA and thermal stability via TGA. The conducted measurements confirmed that the DII system with 45% DEI achieved the most optimal viscosity (0.08 Pa·s at 30 °C), a sufficient reactivity (>80% CC conversion after 120 s), the improved storage modulus at 30 °C (E′30 °C = 447 MPa), and the best thermal stability evaluated by the heat-resistance index (TS = 130.3 °C) of all the investigated systems. Finally, DII with 45% DEI was successfully processed by MSLA additive manufacturing to produce a highly bio-based, 3D-printed polymer prototype.