Rheology of 3D printable ceramic suspensions: effects of non-adsorbing polymer on discontinuous shear thickening
Rheology of 3D printable ceramic suspensions: effects of non-adsorbing polymer on discontinuous shear thickening
复制标题
可 3D 打印陶瓷悬浮液的流变学：非吸附聚合物对不连续剪切增稠的影响
DOI：
10.1039/d2sm01396g
复制
发表时间：
2023
期刊：
影响因子：
3.4
通讯作者：
Erk, Kendra A.
中科院分区：
文献类型：
--
作者：
Corder, Ria D.;Chen, Yuan-Jung;Pibulchinda, Pattiya;Youngblood, Jeffrey P.;Ardekani, Arezoo M.;Erk, Kendra A.
体积分数（η）≥ 0.5的颗粒的浓缩悬浮液通常表现出复杂的流变行为，随着剪切应力或剪切速率的增加，从剪切稀化转变为剪切增稠。这些悬浮液可以挤出形成3D结构，通常添加非吸附性聚合物作为流变改性剂以改善可印刷性。了解非吸附性聚合物如何影响悬浮液流变学，特别是剪切增稠的开始，对于将均匀挤出的颗粒油墨的设计至关重要。在这项工作中，我们研究了胶体氧化铝颗粒的浓缩水悬浮液的流变学和添加非吸附性聚乙烯吡咯烷酮（PVP）的影响。首先，我们表明，悬浮液与氧化铝= 0.560-0.575表现出不连续的剪切增稠（DST），其中粘度增加了高达两个数量级以上的起始应力（τmin）。将α-Al 2 O3从0.550增加到0.575增加了剪切稀化区域中的粘度和屈服应力，并降低了τmin。接下来，将PVP以聚合物构象的稀释和半稀释非缠结方案（PVP = 0.005-0.050）内的浓度添加到具有恒定氧化铝= 0.550的悬浮液中。在所有情况下观察到DST，并且增加PVP的粘度和屈服应力增加。有趣的是，增加α PVP也增加τmin。我们认为游离PVP链在氧化铝颗粒之间起润滑剂的作用，增加了诱导增稠所需的应力。最后，我们通过直接比较含PVP和不含PVP的悬浮液，证明了非吸附性聚合物添加如何由于τmin的增加而延长挤出加工窗口。
Concentrated suspensions of particles at volume fractions (ϕ) ≥ 0.5 often exhibit complex rheological behavior, transitioning from shear thinning to shear thickening as the shear stress or shear rate is increased. These suspensions can be extruded to form 3D structures, with non-adsorbing polymers often added as rheology modifiers to improve printability. Understanding how non-adsorbing polymers affect the suspension rheology, particularly the onset of shear thickening, is critical to the design of particle inks that will extrude uniformly. In this work, we examine the rheology of concentrated aqueous suspensions of colloidal alumina particles and the effects of adding non-adsorbing polyvinylpyrrolidone (PVP). First, we show that suspensions with ϕalumina = 0.560–0.575 exhibited discontinuous shear thickening (DST), where the viscosity increased by up to two orders of magnitude above an onset stress (τmin). Increasing ϕalumina from 0.550 to 0.575 increased the viscosity and yield stress in the shear thinning regime and decreased τmin. Next, PVP was added at concentrations within the dilute and semi-dilute non-entangled regimes of polymer conformation (ϕPVP = 0.005–0.050) to suspensions with constant ϕalumina = 0.550. DST was observed in all cases and increasing ϕPVP increased the viscosity and yield stress. Interestingly, increasing ϕPVP also increased τmin. We posit that the free PVP chains act as lubricants between alumina particles, increasing the stress needed to induce thickening. Finally, we demonstrate through direct comparisons of suspensions with and without PVP how non-adsorbing polymer addition can extend the extrusion processing window due to the increase in τmin.