Composition–property engineering of bio-derived UV-curable acrylate oligoester resins for tunable mechanics in 3D printing†

Liquid Crystal Display (LCD) mask projection stereolithography (MPSL) is a 3D printing technology that enables the fabrication of complex, high-resolution structures; however, the mechanical properties of MPSL 3D printed objects are often limited by the resins used. This study focuses on developing and characterizing bio-based polyester UV-curable resins with tunable mechanical properties optimized for MPSL. Bio-based polyester resins were synthesized by direct esterification and a polycondensation reaction of itaconic and/or succinic acids with 1,2-propane-, 1,4-butane-, and/or 1,8-octanediols, followed by blending with triethylene glycol dimethacrylate. The bio-renewable nature of the resin components provides several advantages over traditional petroleum-derived resins. The diacid and diol monomers come from renewable feedstocks such as corn, soybean, and vegetable oils rather than finite fossil fuel reserves. Furthermore, bio-renewable materials lower dependence on petrochemicals and increase the sustainability of 3D printing. The effects of the diacid structure and diol chain length on resin properties were systematically investigated. Chemical characteristics were investigated by NMR and FTIR, suggesting successful synthesis of the desired bio-based polyesters. By varying the molecular design, diacid, and diol building blocks, the molecular weight, crosslink density, and mechanical performance were tailored. The liquid resins were characterized by gel permeation chromatography and rheological measurements, and solid UV-cured objects were characterized by static and dynamic tensile testing. Rheological studies confirmed that all resin formulations displayed shear-thinning behaviour, ideal for MPSL printing. Mechanical testing revealed that varying diacid and diol components could modulate tensile elastic modulus and elongation at break from 0.1 to 1.0 GPa and 3.5 to 8.5%, respectively. Printability was assessed by printing a resolution test structure on a LCD 3D printer equipped with a 405 nm LED source. This ability to tailor the properties of bio-based polyester resins by molecular design provides an avenue for fabricating high-performance MPSL-printed objects targeted for specific applications, ranging from prototypes to end-use products.