Renewable Methacrylate Resins for 3D Printing Containing Dynamic Hydroxyester Linkages for Reprocessability

Abstract

To facilitate the ongoing transition toward a circular economy, renewable 3D print materials that are both sustainable and competitive must be accessible. However, the growing demand for bio-based thermosetting resins, which are used as ink for vat photopolymerization, gives rise to environmental concerns in terms of plastic waste management. Therefore, photocurable materials that are renewable and recyclable at the same time are needed. In this work, a mechanically robust and reprocessable 3D printed photopolymer is developed from renewable feedstock. Reaction of malic acid with glycidyl methacrylate introduces both methacrylate moieties that can undergo photopolymerization in the 3D printer, and β-hydroxyester linkages that can act as dynamic crosslinks via bond exchange reactions. By combining modified malic acid with reactive diluents, a photoinitiator, and phosphate catalyst, three distinct resins are formulated, resulting in bio-based contents ranging from 43% to 49%. The formulations demonstrate good layer fusion and accurate print quality, while the 3D printed specimens are robust and thermally stable. Notably, the printed object with shortest relaxation time displayed Arrhenius flow behavior with an activation energy of 36.0 kJ mol⁻¹, and its mechanical performance is maintained after being recycled three times. This contributes to the end-of-life perspective of photocurable resins in additive manufacturing.