Self-standing and shape-memorable UV-curing epoxy polymers for three-dimensional (3D) continuous-filament printingElectronic supplementary information (ESI) available. See DOI: 10.1039/c7tc04873d

• Main Authors: Sun, H, Kim, Y, Kim, Y. C, Park, I. K, Suhr, J, Byun, D, Choi, H. R, Kuk, K, Baek, O. H, Jung, Y. K, Choi, H. J, Kim, K. J, Nam, J. D
• Format: Journal Article
• Language: English
• Published: 22.03.2018
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/c7tc04873d

In the development of three-dimensional printable materials for high-speed and high-resolution printing, UV-curing polymers can guarantee fast and precise printing of high performance load-bearing structures, but the injected drops of the monomers tend to spread over the substrates due to their low viscosity. In this study, we imposed the self-standing and shape-memorable capability of an epoxy acrylate (EA) monomer to ensure continuous filamentary 3D printing while maintaining its low viscosity nature. Using octadecanamide (ODA) with EA, strong hydrogen-bond networks (−N−H O&z.dbd;C−, −N−C&z.dbd;O H-O-, -N-H N-) were additionally achieved in the material system and the developed material distinctively exhibited rheological duality at different processing stages: a low-viscosity liquid-like behavior (viscosity of ∼50 Pa) while passing through the nozzle and a self-standing solid-like behavior (static yield stress of ∼364 Pa) right after being printed. This reversible liquid-to-solid transitional capability was quantified by viscoelastic complex moduli provided a dynamic yield stress ( τ y,G ) of 210 Pa corresponding to the upright stacking up to ∼3.2 cm (3 wt% of ODA). The time ( t y,G ) required for conformational rearrangement was evaluated to be as fast as ∼10 −2 s. After UV curing, the 3D printed layers exhibited no air pockets or weld lines at the stacked interfaces, which could guarantee excellent mechanical performance and structural integrity. Hydrogen-bond networks with adjacent molecules were formed to provide a developed material, which has self-standing solid-like characteristics enabling its implementation in 3D continuous-filament printing.