Effect of Diluent Structure on the 3D Printed Dual-Cured Polyurethane

Diluents play a critical role in dual-cured polyurethane systems that incorporate both photo and thermal curing mechanisms. Currently, the diluents employed in such systems are predominantly acrylate monomers, with limited exploration of non-acrylate alternatives. Based on this, we selected three diluents for deep study: 4-acryloylmorpholine (ACMO), isodecyl acrylate (IDA), and vinyl ethylene carbonate (VEC) used in Non-isocyanate Polyurethane (NIPU) synthesis. The key factor influencing viscosity was identified as the electrostatic interaction energy between diluent and prepolymer molecules. Compared with ACMO and IDA, the dilution efficiency of VEC was improved by 38.6% and 15.6%, respectively, owing to its higher polarity. VEC remains a small molecule within the system and functions as a plasticizer, leading to improved plasticity of the final material. In contrast, both IDA and ACMO participate in polymerization, forming a secondary network. The distinction lies in their structural contribution: the rigid morpholine ring in ACMO improves the toughness of the material, whereas the flexible chain of IDA imparts notable resilience to the dual-cured polyurethane. These findings advance the understanding of the relationship between diluent structure and the viscosity of the prepolymer and the performance of dual-cured polyurethanes, thereby providing a theoretical foundation for the developing 3D-printable polyurethane materials. Highlights VEC, a monomer from NIPU synthesis, is introduced as an efficient plasticizing diluent. Electrostatic interaction, rather than van der Waals forces, governs diluent efficiency in polyurethane resins. Diluent structure dictates properties: rigid rings boost toughness, flexible chains impart resilience.