Rheological Parameters of Shear-Thickening Fluids Using an Experimental Design

Abstract: The influence of important factors related to fluid preparation on shear-thickening fluids (STF) is not well explored in literature. Thus, this paper aimed at analyzing the statistical significance of experimental conditions, such as fumed silica concentration (Cs), stirring time (tst), stirring speed (Sst) and sonication time (tso ), on the rheological behavior of fumed silica particles and PEG 400 dispersions. For that, a 2k factorial Experimental Design (DOE), with three center points, was accomplished. The investigated response variables were: maximum viscosity (ηm); critical shear rate ( γ ˙ m) where the viscosity is maximum; and agglomerate size of particles during preparation (R). All factors were statistically significant for all three response variables. Higher viscosity values for shear rate range analyzed was obtained with longer tst, lower Sst and longer tso. An important contribution of this paper was to show discontinuous shear thickening (DST) for lower concentrations than previously found in literature only changing the preparation protocol.

摘要：目前学界对流体制备相关重要因素对剪切增稠流体（shear-thickening fluids, STF）的影响尚未得到充分研究。为此，本文旨在分析气相二氧化硅浓度(C_s)、搅拌时间(t_st)、搅拌转速(S_st)及超声时间(t_so)等实验条件，对气相二氧化硅颗粒与聚乙二醇400（PEG 400）分散体系流变行为的统计学显著性影响。本文采用了含3个中心点的二水平k因子实验设计（Design of Experiments, DOE）开展研究。所考察的响应变量包括：最大黏度(ηₘ)、黏度达到峰值时的临界剪切速率(γ̇_m)，以及制备过程中的颗粒团聚体尺寸(R)。所有实验因素对上述三类响应变量均具有统计学显著性。当采用更长的搅拌时间、更低的搅拌转速以及更长的超声时间时，在所考察的剪切速率范围内可获得更高的黏度值。本文的一项重要贡献在于：仅通过调整制备工艺，即可在低于此前文献报道的浓度下实现不连续剪切增稠（discontinuous shear thickening, DST）。