Products Cited in Publications Worldwide DLP 3D printing of materials with heterogeneous material properties

DLP 3D printing of materials with heterogeneous material properties

Šebalj, Nikola

Abstract

With additive manufacturing, it is now possible to repeatedly create 3D objects without the need for molds or heavy machining. In comparison with other additive manufacturing techniques, vat photopolymerization provides a fast and precise way of producing complex shapes and objects. Photopolymerization 3D printing uses light exposure to solidify a resin formulation and is typically limited to a single material. In recent years, researchers have focused on using multi-material 3D printing to manufacture objects with heterogeneous properties. A promising approach for vat photopolymerization 3D printing of multi-material objects is the use of orthogonal photoreactions to tailor the network properties. In this work, three different hybrid acrylate-epoxide systems were formulated to present the possibility of preparing dual-curable resins for 3D printing, and tuning their properties using dual-wavelength DLP 3D printing technology: a) DOM:ECC = 75:25, 25:75 b) Eb:ECC = 25:75 c) PEGDA:ECC = 50:50 The 3D printer used in this work, employs two different light engines, operating at 405 and 365 nm. At visible light irradiation, a radical photoinitiator was selectively activated, leading to the curing of the acrylate component. Upon UV light exposure, a radical curing as well as cationic ring opening process of the epoxide component was initiated, yielding an interpenetrating network (IPN) with higher crosslinking density and stiffness. For the quantitative conversion of the epoxide network, a thermal post-baking step was carried out at 120°C for 2 hours. The cure kinetics of prepared hybrid acrylate-epoxide resins were investigated using the FTIR spectroscopy and through the initial printing trials. Selective illumination with either light source should shift material properties between the soft acrylate and rather stiff epoxide network. This was verified for DOM:ECC and PEGDA:ECC systems, while the system Eb:ECC displayed thermal instability and inability to print wavelength selective materials. The system Eb:ECC was not subjected to further testing. Furthermore, to investigate mechanical behavior of the printed samples, dynamical mechanical analysis and tensile test were carried out.

Keywords

DLP 3D printing ; dual-curable resins ; radical and cationic polymerization ; acrylate and epoxide ; mechanical properties

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