Three-dimensional (3D) printing of biomaterials has the potential to become an ecologically advantageous alternative compared with conventional manufacturing based on oil-derived polymer materials. In this study, a novel 3D printing technology is applied that combines ultraviolet (UV) curing with paste extrusion. This hybrid manufacturing technique enables the fabrication of complex geometries from high filler-ratio pastes. The developed biocomposite aims for suitable mechanical properties in terms of tensile and compressive strength. It is composed of acrylic acid, cellulose acetate, α-cellulose, and fumed silica with a cellulose ratio of more than 25 vol-%. The material is extruded with an in-house-developed 3D printer equipped with a 12 W UV light curing source, which enables concurrent curing and extrusion. Two different UV-curing strategies were tested: postcuring without concurrent curing and postcuring with concurrent curing. The total UV-curing duration was kept constant with all samples. Tensile testing in accordance with ASTM standard D638-14 Type 4, compression testing according to ASTM D695-15, and overhang tests were conducted. As a result, samples without notable shrinkage, suitable tensile strength (up to 17.72 MPa), competitive compression testing parameters (up to 19.73 MPa), and an enhanced overhang angle (increase of more than 25) were produced, leading to new applications and more freedom in design due to higher possible unsupported overhangs when using UV-curing during the print. Overall, constant UV light radiation during the print leads to improved mechanical properties due to the possibility of bypassing the UV-penetration depth constraint. It should be considered when extruding photopolymer-based composites, especially for large and complex components with a low degree of translucency.

Mechanical Properties of Ultraviolet-Assisted Paste Extrusion and Postextrusion-3dp.2019.6.issue-3.cover.jpg

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