中等浓度表面活性剂溶液流变特性的实验研究

为研究剪切速率和溶液浓度对中等浓度表面活性剂溶液流变特性的影响,在25℃、1～300s-1剪切速率范围内,对质量分数分别为0.05%、0.07%、0.10%和0.15%的CTAC/NaSal表面活性剂溶液进行稳态模式下的流变测量.研究表明,随着表面活性剂浓度的增大,由剪切诱导转变引起的黏度增稠率依次减小,当浓度达到某一临界饱和值时不再有剪切诱导转变发生,该浓度所对应的黏度-剪切速率流变曲线称为最大黏度线.当浓度低于临界饱和浓度时,在以临界剪切速率为界的两区域内,剪切速率-剪切应力流变曲线分别符合对数模型.从能量的视角分析了剪切诱导结构(SIS)可能的形成机理,指出诱导SIS形成的临界能量值本质上是由胶束结构决定的.从流变的角度指出,对于中等浓度的表面活性剂溶液,SIS不再是产生湍流减阻的必要条件.

Experimental Study on Rheological Properties of Semidilute Surfactant Solutions

In order to investigate the effects of concentration and shear rate on rheological properties of semidilute surfactant solutions,CTAC/NaSal aqueous solutions with four mass fractions of 0.05%,0.07%,0.10%,and 0.15% were measured under the conditions of 25 ℃ and 1-300 s-1.The results show that the viscosity thickening rate caused by shear-induced transition decreases with an increase in the surfactant concentration at the same temperature until a critical saturation concentration arises.When the surfactant concentration is less than the critical saturation concentration,the shear rate-shear stress rheology curve σ(γ) satisfies the logarithm law in two regions of 1 s-1 to the critical shear rate and the critical shear rate to 300 s-1.Once the concentration reaches the critical saturation concentration,there is no shear-induced transition and the viscosity curve η(γ) at the critical saturation concentration is the maximum viscosity one.The possible formation mechanism of shear-induced structure(SIS) is presented by the shear energy analysis of the system.From the rheology,the SIS is no longer the necessary condition to generate turbulent drag reduction for semidilute surfactant solutions.