(162f) Rheology of Highly-Loaded Polymer-Ceramic Suspensions for Direct-Ink-Writing 3D Printing

Suspensions of ceramic particles are used in electronics manufacturing to improve heat and/or electron transfer between components, with polymers often added to improve the flow behavior at high particle loadings. These suspensions can be rapidly fabricated into custom and precise structures via direct-ink-writing 3D printing; however, deposition of excess material often occurs when the nozzle is lifted and moved to a new location (also called “tailing”), which results in material wastage and sample defects. In this work, we examine the rheology of depletion-stabilized aqueous suspensions containing >50 vol% alumina nanoparticles and polyvinylpyrrolidone (PVP). Discontinuous shear-thickening (DST) is observed at high shear rates for suspensions with high alumina loadings. We demonstrate how varying the relative component volume fractions and the PVP molecular weight affect the presence and onset of DST. We further probe how shear history affects the steady-shear and oscillatory rheology, highlighting the need for consistent experimental protocols to achieve reproducible data. Finally, we present results from direct-ink-writing tests and observe how both suspension composition and varying printing parameters (e.g. nozzle diameter, flow rate, print speed) affect tailing behavior. The process-structure-property relationships elucidated herein can help inform the design of 3D-printable polymer-ceramic suspensions.