3D printing and post-curing optimization of photopolymerized structures: Basic concepts and effective tools for improved thermomechanical properties

The final thermo-mechanical properties of structural parts fabricated by masked stereolithography (MSLA) are highly determined not only by the processing parameters, but also by the post-processing methods. Improper implementation of post-treatment often leads to underperforming printouts. A novel tool for complex characterization of 3D printed bodies was developed and systematically demonstrated on a commercial free-radical photopolymerization (FRP) resin. The method relies on superimposed static and oscillatory mechanical test combining the heat deflection temperature (HDT) measurement together with the dynamic mechanical analysis (DMA) in a single test for fast and reliable characterization of parameters determining the curing behaviour of the photopolymer. The influence of post-curing time was addressed with a special focus on network density. Furthermore, the print orientation, having a high impact on mechanical properties, is discussed with a particular regard on the residual stress mitigation in future applications, such as 3D-printed cellular bodies