Synthesis and characterization of a dual-curing resin for three-dimensional printing

The adipic acid glycidyl methacrylate (AA-GMA) containing double bond of carbon and hydroxyl as an ultraviolet-polyurethane dual-curing oligomer was prepared as a precursor to resin for three-dimensional (3D) printing. A dual-curing resin for 3D printing was formulated from the AA-GMA, PHDI (hexamethylene diisocyanate-based polyisocyanates, mainly trimer) and other reagents. The dual-curing oligomer AA-GMA was synthesized by the epoxide ring-opening reaction with dicarboxylic acid and the molecular structure of which was characterized by FTIR and ¹H NMR analyses. AA-GMA has the double bond which could be cured via ultraviolet irradiation in the 3D printing process, and the hydroxyl could be cured by PU curing agent PHDI at the thermal post-curing process. The PHDI was not only employed as a diluent in the 3D printing process, but also acted as a reactant for post-curing. Compared to the traditional single-curing resin, this dual-curing resin could provide products with increased crosslinking density, flexibility and reduced volumetric shrinkage rate. The tensile strength of dual-curing sample was improved to 64 MPa after adding 20 wt% PHDI, which showed 18% boost compared to the sample without the PHDI. For the sample with a content of 30 wt% PHDI, the glass transition temperature (T_g) was about 121 °C, presenting 35 °C higher than that of the blank sample.