UV-Curing Additive Manufacturing of Bio-Based Thermosets: Effect of Diluent Concentration on Printing and Material Properties of Itaconic Acid-Based Materials

In the quest toward sustainable thermosets, researchhas been conductedon various polymer classes like epoxy, benzoxazines, acryl-/methacrylates,etc. One particular group that can also be utilized as sustainableinks for additive manufacturing is itaconic acid-based unsaturatedpolyester resins. However, due to increased viscosity of the resins,the use of reactive diluents is required to increase their processability.While research has focused on creating different polymeric structuresto expand the possible applications, the required amount of diluenthas not received equal attention. In this work, a group of itaconicacid-based polyesters was synthesized to create a series of formulationswith different reactive diluent contents. The physicochemical propertiesof the prepared formulations, along with their reactivity toward UVlight, were assessed via photo-differential scanning calorimetry (photo-DSC),real-time attenuated total reflectance (RT-ATR), and photorheologymeasurements. The same formulations were then used to fabricate testspecimens via digital light processing (DLP) three-dimensional (3D)printing, which were examined as to their thermomechanical propertiesby means of dynamic mechanical analysis (DMA) and thermogravimetricanalysis (TGA) measurements.