Influence of Postprinting Conditions on Morphologies in a Three- Dimensional Printable Dual-Cure Interpenetrating Dimethacrylate/ Epoxy Polymer Network

A dual-curing dimethacrylate/epoxy resin system was found to retain printed resolution after photocuring by digital light processing three-dimensional (3D) printing, and after a subsequent heating step, it had a glass transition temperature of up to 140 degrees C. Postprinting curing conditions were shown to influence the morphology of the fully cured structure, depending on the rate of epoxy polymerization by dynamic mechanical analysis (DMA). Curing of the epoxy component by heating to 180 degrees C immediately after UV exposure created a partially miscible, phase-separated structure, while delayed curing (dark curing at ambient temperature for long times, up to 5 weeks) resulted in a single, broad tan delta peak in DMA, indicating a miscible network system with no macroscale phase separation. This dispersion of the epoxy-amine monomers into the photopolymerized dimethacrylate polymer over long times is surprising and is attributed to lower critical solution temperature behavior of these two polymer systems. The resulting phase structure of the sequential interpenetrating polymer network was found to influence the thermal and mechanical properties of the finished 3D-printed article.