Sterelithography (SL) is an additive manufacturing technique that uses high energy light in the ultraviolet or visible range to solidify liquid resins into thin layers and build 3-dimensional objects layer by layer. SL is in high demand for small-volume manufacturing and rapid prototyping because of its ability to relatively quickly create objects with intricate feature at resolutions down to 150 µm. Widespread adoption of SL faces a number of obstacles including slow print speeds, unsuitable thermomechanical properties, and anisotropic properties. In this work, we attempt to overcome many of these challenges by incorporating a small concentration of a reversible addition-fragmentation chain transfer (RAFT) agent into an acrylate formulation to control the morphology of the propagating cross-linked network in objects printed using DMD SL. Incorporating a small amount of a trithiocarbonate RAFT agent into the formulation leads to a 45% increase in elongation and toughness while incurring a 20% decrease in Young’s modulus compared to a sample without the RAFT agent. The anisotropic properties of DMD SL were measured by printing dogbones in the “horizontal” or “vertical” direction, where the long axis of the dogbone was printed in the x- axis or z-axis, respectively. The model acrylate formulation exhibits a 33% decrease in modulus when printed in the vertical orientation, compared to the same formulation printed horizontally. However, this effect is diminished when a RAFT agent is incorporated into the acrylate formulation, indicating that the inclusion of a RAFT agent facilitates better interlayer adhesion that can diminish the effect of print orientation on anisotropic properties.

Improving anisotropic properties of objects printed via stereolithography

255th National Meeting (2018)

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