Isocyanate-free urethanediol itaconates as biobased liquid monomers in photopolymerization-based 3D printing

Nowadays, most of the commercial resins for VP are composed of (meth)acrylated urethanes, as they are cheap and provide good mechanical properties to the thermosets produced by their photocuring. However, such urethanes are still produced using toxic and polluting isocyanates, though alternative pathways exploiting cyclic carbonates and biobased amines are arising. Unfortunately, the use of biobased amines and carbonates to produce (meth)acrylate urethanes often leads to the formation of solid products that display poor solubility in the liquid components of photocurable resins. In this work, we describe the synthesis of fully biobased diurethanediols using a biobased diamine and bioderived carbonates functionalized with itaconic acid moieties that are liquid at room temperature and that can be efficiently formulated with (meth)acrylic and itaconic acid-based formulations for VP leading to 3D printed materials with good mechanical properties, comparable to those of commercially available non-biobased alternatives. In fact, depending on the resin formulations, the addition of diurethanediols diitaconates led to the obtainment of 3D printed materials with elastic moduli as high as 1 GPa, and tensile strengths over 30 MPa, and biobased contents as high as 90 wt.%. These products may serve as candidates for the replacement of isocyanate-based components with the aim of increasing the sustainability of resins’ manufacturing for VP.