Shear and Extensional Rheology of Cellulose/Ionic Liquid Solutions
Shear and Extensional Rheology of Cellulose/Ionic Liquid Solutions
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DOI：
10.1021/bm300407q
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发表时间：
2012-05-01
影响因子：
6.2
通讯作者：
Rahatekar, Sameer S.
中科院分区：
文献类型：
--
作者：
Haward, Simon J.;Sharma, Vivek;Rahatekar, Sameer S.
在这项研究中，我们的特点是剪切和拉伸流变稀到半稀溶液的纤维素在离子液体1-乙基-3-甲基咪唑乙酸盐（EMIAC）。在稳定的剪切流中，semidilute解决方案表现出剪切稀化，和高频率的复模量在小振幅振荡剪切流中测量表现出预期的半柔性链的解决方案的特征缩放。稳态剪切粘度对剪切速率绘制的流动曲线密切遵循使用振荡剪切获得的复数粘度的频率依赖性，从而满足经验Cox-Merz规则。我们使用毛细管变稀流变仪（CaBER）的松弛时间和表观拉伸粘度的半稀纤维素溶液在单轴拉伸流，模仿在纺丝过程中遇到的动态纺丝线的特征。半稀纤维素/EMIAc溶液的表观拉伸粘度和特征松弛时间随着溶液进入纤维纺丝变得可行的缠结浓度范围而急剧增加。
In this study, we characterize the shear and extensional rheology of dilute to semidilute solutions of cellulose in the ionic liquid 1-ethyl-3-methylimidazolium acetate (EMIAc). In steady shear flow, the semidilute solutions exhibit shear thinning, and the high-frequency complex modulus measured in small amplitude oscillatory shear flow exhibits the characteristic scaling expected for solutions of semiflexible chains. Flow curves of the steady shear viscosity plotted against shear rate closely follow the frequency dependence of the complex viscosity acquired using oscillatory shear, thus satisfying the empirical Cox-Merz rule. We use capillary thinning rheometry (CaBER) to characterize the relaxation times and apparent extensional viscosities of the semidilute cellulose solutions in a uniaxial extensional flow that mimics the dynamics encountered in the spin-line during fiber spinning processes. The apparent extensional viscosity and characteristic relaxation times of the semidilute cellulose/EMIAc solutions increase dramatically as the solutions enter the entangled concentration regime at which fiber spinning becomes viable.