SiO2/PEG分散体系动态剪切流变行为

在动态应变条件下, SiO2/PEG200(聚乙二醇, 平均分子量为200)分散体系出现了剪切增稠现象. 剪切流变实验表明, 在两种情况下都出现了剪切增稠: 一种是在不同的恒定频率下应变扫描, 在临界应力γc出现的剪切增稠; 另一种是恒定的应变(γ0=500%)条件下频率扫描, 在临界频率棕c抑10 rad·s-1出现的剪切增稠. 在不同的恒定频率应变扫描条件下, 实验研究了储能模量(G’)和耗能模量(G’’)与应变的关系, 同时初步探讨了应变与不同恒定频率的函数关系. 在线性粘弹性区域内, G’和G’’满足G’∝ω0.57和G’’∝ω0.7指数关系. 在恒定的应变条件下, 发现模量和复数粘度与扫描频率具有强烈的依赖关系, 这些现象可以定性地通过“粒子簇”理论来解释.“粒子簇”理论认为这种剪切增稠的发生是由于形成了亚稳定、流动所导致的“粒子簇”, 使得粘度上升.

Rheological Behaviors of SiO2/PEG Suspension under Dynamic Shear

Fumed silica suspensions in polyethylene glycol(PEG200)exhibited shear-thickening behavior under dynamic oscillatory strain amplitude.Two regimes of shear-thickening behavior were obtained:the first occurred at critical strain amplitude γc and different constant frequencies,and the second occurred at critical frequency and constant strainamplitude γo=500%.For the fast,the relationships ofboth of the moduli(G'and G″)versus strain amplitude were investigated.The strain amplitude as a function of difierent constant frequencies Was observed.In the linear viscoelastic region,the storage(G′)and the loss((G″)moduli depended strongly on frequency with the power-law:G′∝ ω0.57,G″∝0.7.In the second regime,the moduli(G′and G″)and complex viscosity η* showed strong dependence on frequency.The behaviors could be qualitatively explained using the cluster theory,which attributed the phenomena to the formation of metastable.flow induced clusters.