Morphological Effects of Various Silica Nanostructures on the Mechanical Properties of Printed Parts in Digital Light Projection 3D Printing

Nanostructured silica particles are common additives in polymer-based coating applications and therefore of great interest to obtain better properties of light-curable three-dimensional (3D) printed polymer parts. This work studies the effect of nanostructured silica additives on the mechanical properties of printed parts. Three types of silica particles with distinct nanostructured morphologies, namely, (1) fumed fractal silica, (2) sponge-like precipitated silica, and (3) discrete colloidal silica, were used as additives to prepare nanocomposite photopolymer resins for the digital light projection (DLP) 3D printing. The effect of particulate nanostructures and their interfacial interactions with the resin matrices on the rheology of resin constituents, the curing, and mechanical properties were evaluated. The addition of 10 wt % fumed or precipitated silica improved the mechanical properties such as hardness and tensile strength by as much as 58 and 141%, respectively. Sponge-like precipitated silica tends to lower the critical energy of photopolymerization by up to 17%. The findings in this work provide useful guidelines when tailoring the mechanical properties of 3D printed parts with nanostructured silica additives. In the quest for light-curable printing materials, while the strategy to modify/alternate polymer backbone structures to achieve higher mechanical strength is important, the means of obtaining such enhancement through “printing suitable filler”–polymer matrix interaction have indeed proved to be a target within immediate reach.