SiO_2/聚乙二醇非牛顿流体流变性能研究

Study on the Rheological Properties of Silica /Polyethylene Glycol Non-Newtonian Flow

利用应力控制流变仪考察了SiO2/聚乙二醇分散体系稳态和动态的流变性能.实验结果表明,该体系具有剪切变稀和可逆的剪切增稠现象.稳态应力实验中,当应力较小时,体系具有剪切变稀现象,而在剪切应力(!)大于临界剪切应力(!cs,!cs=9.99Pa)后,体系粘度急剧增大.在动态实验中,剪切应力小于临界剪切应力(!oc,!oc=15.85Pa)时,储能模量G′减小,耗能模量G″与复合粘度η!基本不变,但!>15.85Pa后,G′、G″及η!同步增大,且在所研究的应力范围内,G″均大于G′.同时还考察了测试频率、分散相含量以及分散介质平均分子量的差别对流变性的影响.!oc随测试频率的增大而变大;SiO2质量分数越大,!oc基本不变,但增稠现象变得更明显;与平均分子量小的PEG200体系相比,平均分子量大的PEG400体系,!oc并未发生改变,但在增稠之前体系的粘度较低,增稠之后体系粘度增大的幅度较大.

The rheological properties of dispersions of silica in polyethylene glycol （PEG） have been studied under steady and oscillation stress shear performed on AR2000 stress controlled rheometer. The system shows shear thinning and reversible shear thickening behavior. Under steady stress shear, when the stress is less than the critical stress 9.99 Pa （σ〈σc^s）, the system shows shear thinning, while, the system shows shear thickening when σ〉 σc^s. Under oscillatory stress shear, when the shear stress is less than the critical stress 15.85 Pa （σ〈 σc^o）,storage modulus （G＇） decreases, loss modulus （G＂）, and the complex viscosity （η^＊） almost remain unchanged; but when σ〉 σc^o, G＇ ,G″ and 7/＊ increase synchronously. The magnitude of G″ is larger than the magnitude of G＇ in the range of stress studied. The higher frequency used in the experiment leads to the larger value of the critical stress. The systems almost have the same values of the σ as the SiO2 mass fraction increasing, but the shear thickening phenomena are more obvious. Compared with the dispersion in PEG200, the dispersion in PEG400 shows lower complex viscosity before the critical point and a more sharp increase in the viscosity beyond the point, but has the same value of the critical stress （σc^o） and comparative viscosity at high stresses.