Advancing green additive manufacturing: Epoxidized vegetable oils for room-temperature photopolymerization 3D printing

This work reports, for the first time, renewable biobased epoxy formulations specifically designed for conventional VAT 3D printing under low light intensity, at room temperature, and in the complete absence of acrylic monomers. No previous study has described photocurable systems with these combined characteristics. The epoxy monomers were synthesized from three renewable feedstocks—macaw palm, grapeseed, and castor oils—via a green, efficient, and rapid epoxidation route that achieved full conversion of double bonds. Epoxidized macaw palm oil (EMPO), due to its low viscosity, was employed as a reactive diluent in binary formulations. Cationic photopolymerization was initiated through charge transfer complexes (CTCs) formed by either isopropyl-9H-thioxanthen-9-one (ITX) or curcumin (CUR), combined with an iodonium borate photoinitiator. The photocurable systems reached epoxy conversions of 60–78 % within 120 s of irradiation. All formulations exhibited high renewability metrics, with bio-based content >97 %, bio-based carbon >50 %, and gel fractions >99 %. DMA confirmed the influence of epoxidized grapeseed and castor oils on glass transition temperature and crosslinking density. Notably, all ITX-based systems enabled the successful 3D printing of complex structures, establishing a novel route for sustainable, high-performance resins in additive manufacturing.