Bio-based additive manufacturing materials: An in-depth structure-property relationship study of UV-curing polyesters from itaconic acid

A series of bio-based polyester derived from itaconic acid was synthesized as alternative binder resin to polyester acrylates in UV-curing additive manufacturing processes. Different diols and dicarboxylic acids from both petrochemical and renewable resources were combined to create polyester structures that have not been previously described. Employing these monomers allowed for the synthesis of novel polyester resins with a bio-based content from 56 to 100%. The influence of the different chemical structures (double bond density, flexibility, aromatic content, etc.) of these itaconic acid-based materials on the physicochemical properties was thoroughly investigated for the first time. Subsequently, formulations derived from these polyesters were prepared and processed on a digital light processing (DLP)-machine to obtain test specimen. Mechanical and thermal characterization of cured parts revealed a dependency of the properties on both choice of monomers and crosslink density. Cyclic structures in the polyester resin resulted in very rigid materials with glass transition temperatures up to 97 °C and tensile modulus of 2400 MPa. The incorporation of longer aliphatic chains on the other hand gave rise to flexible materials with an elongation at break up to 50%. Hence, the materials described herein allow for additive manufacturing materials with tunable properties and an overall bio-based content up to 85%.