Balancing Functionality and Printability: High-Loading Polymer Resins for Direct Ink Writing

Abstract

Although direct ink writing (DIW) allows the rapid fabrication of unique 3D printed objects, the resins—or “inks”—available for this technique are in short supply and often offer little functionality, leading to the development of new, custom inks. However, when creating new inks, the ability of the ink to lead to a successful print, or the “printability,” must be considered. Thus, this work examined the effect of filler composition/concentration, printing parameters, and lattice structure on the printability of new polysiloxane inks incorporating high concentrations (50–70 wt%) of metallic and ceramic fillers as well as emulsions. Results suggest that strut diameter and spacing ratio have the most influence on the printability of DIW materials and that the printability of silica- and metal-filled inks is more predictable than ceramic-filled inks. Additionally, higher filler loadings and SC geometries led to stiffer printed parts than lower loadings and FCT geometries, and metal-filled inks were more thermally stable than ceramic-filled inks. The findings in this work provide important insights into the tradeoffs associated with the development of unique and/or multifunctional DIW inks, printability, and the final material’s performance.

Additively Manufactured Silicone Polymer Composite with High Hydrogen Getter Content and Hydrogen Absorption Capacity

“…Once the resin is extruded and deposited, the stress is removed, and the resin regains its original viscoelastic properties, which allows the resin to retain its printed shape. For DIW applications, the printing resin should have G ′ eq and σ y in a certain range for the resin to flow through the nozzle and retain its printed shape after deposition . While resins with low G ′ eq and σ y have difficulties retaining their printed shapes, resins with high G ′ eq have difficulties flowing out of the nozzle, regardless of the nozzle size or flow rate.…”

“…As shown in Figure , all of the polymer getter composite resins formulated in this study exhibited a shear thinning yield stress and a rubbery plateau region. In general, the printing resin for DIW application should have G ′ eq and σ y in the range of 43,000–2,800,000 Pa and 2,000–11,500 Pa respectively, for the resin to flow through the nozzle and retain its printed shape after deposition . The polymer getter composite resin, 10 wt % getter + 13 wt % TS720, has very low G ′ eq and σ y (<129 Pa and <36,720 Pa, respectively), and the polymer getter composite resin, 65 wt % getter + 1 wt % A300, has very high G ′ eq (>18,583,800 Pa), suggesting that these resins are not suitable for DIW feedstock.…”

“…For DIW applications, the printing resin should have G ′ eq and σ y in a certain range for the resin to flow through the nozzle and retain its printed shape after deposition. 24 While resins with low G ′ eq and σ y have difficulties retaining their printed shapes, resins with high G ′ eq have difficulties flowing out of the nozzle, regardless of the nozzle size or flow rate. In this study, a series of polymer getter composite resins were formulated by adding different amounts of getter and filler, and their rheological properties were studied by measuring the oscillatory amplitude at an angular frequency of 10 rad/s from 10 to 10,000 Pa.…”

Boron‐polymer composites engineered for compression molding, foaming, and additive manufacturing

“…Formulation of DIW resins was performed in a similar fashion as previously reported by this group 34 . Trimethylsiloxy‐terminated methylhydrosiloxane‐dimethylsiloxane copolymer (HMS‐301; Gelest Inc., USA) and 1‐ethynyl‐1‐cyclohexanol (ETCH; 99%; Sigma Aldrich, USA) (3.25 and 0.50 wt%, respectively) were added to a 100 mL disposable THINKY cup and put into an ARV‐310 THINKY Mixer where they were mixed for 5 minutes in a cold fixture.…”

“…Formulation of DIW resins was performed in a similar fashion as previously reported by this group. 34 Trimethylsiloxy-terminated methylhydrosiloxanedimethylsiloxane copolymer (HMS-301; Gelest Inc., USA) and 1-ethynyl-1-cyclohexanol (ETCH; 99%; Sigma Aldrich, USA) (3.25 and 0.50 wt%, respectively) were added to a 100 mL disposable THINKY cup and put into an ARV-310 THINKY Mixer where they were mixed for 5 minutes in a cold fixture. Boron powder, vinylterminated (4%-6% diphenylsiloxane)-dimethylsiloxane copolymer (PDV-541; Gelest Inc., USA) and hydroxide (OH)-functionalized fumed silica (A300; Evonik Aerosil 300; Evonik Industries AG, Germany) were added (65, 30.15, and 1.00 wt%, respectively) to the mixture and spun in the THINKY mixer for another 5 minutes at 2000 rpm.…”