Silicone Rheological Properties for Material Extrusion Additive Manufacturing

Abstract

Additive manufacturing (AM), known as three-dimensional (3D) printing, uses computer-controlled materials deposition to fabricate 3D objects by selectively depositing materials, usually in a layer-wised fashion, to build a 3D object using free-form fabrication. Integrating silicone elastomers with AM deposition strategies has been of interest due to the important application characteristics of silicones such as excellent mechanical properties, thermal resistance, and chemical inertness. This work presents a study on the shear-thinning properties of thermally-curable liquid silicone feedstocks to describe ideal flow and shape-retention properties for direct ink writing of liquid silicone rubbers. To complement the direct ink writing process developed in this work for silicone AM, flow properties of various silicone feedstocks were identified through measurement of rheological properties using the AM fluid dispenser under various pressures, supported by parallel plate oscillatory shear rheology. A systematic process for evaluating and investigating the AM performance of seven different grades of silicones is introduced. The shape retention, overhang, and dimensional accuracy of these silicones in 3D printing process have been compared and summarized. This systematic evaluation methodology can be applied for silicone material selection and printing of silicone parts with complicated architectures.