Inoue Tadashi, Inoue Yoshitaka, Watanabe Hiroshi
Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan.
Langmuir. 2005 Feb 15;21(4):1201-8. doi: 10.1021/la048292v.
The nonlinear rheology of aqueous solutions of cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal) was investigated. The concentration of CTAB was fixed at 0.1 mol L(-1), and the concentration of NaSal was varied from 0.07 to 0.4 mol L(-1). For all test solutions, dynamic moduli were described with the Maxwell model having a single relaxation time, tau. Time evolutions of the shear stress, sigma, and the first normal stress difference, N(1), after inception of the steady shear flow were measured. For solutions having low NaSal concentrations, strain-hardening was observed and sigma and N(1) diverged at a certain strain when the shear rate, , exceeded tau(-1). For solutions with high NaSal concentrations, stress overshoot similar to that of ordinary entangled polymer solutions was observed at between tau(-1) and a certain critical rate, (C), while the strain-hardening was observed at > (C). A simple relationship for elastic solids, N(1)/sigma = gamma with gamma being the strain imposed by shear flow, held for all the solutions in the strain-hardening regime. The strain-hardening was attributable to the strain-dependent shear modulus and well described with the network theory considering the finite extensibility of network strands. The segment size of network strands was successfully determined. Thus, the stress-strain relationship obtained after the inception of fast flows is useful for characterizing the network properties.
研究了十六烷基三甲基溴化铵（CTAB）和水杨酸钠（NaSal）水溶液的非线性流变学。CTAB的浓度固定为0.1 mol L⁻¹，NaSal的浓度在0.07至0.4 mol L⁻¹之间变化。对于所有测试溶液，用具有单一弛豫时间τ的麦克斯韦模型描述动态模量。测量了稳态剪切流开始后剪切应力σ和第一法向应力差N₁随时间的演变。对于低NaSal浓度的溶液，观察到应变硬化，当剪切速率γ超过τ⁻¹时，σ和N₁在一定应变下发散。对于高NaSal浓度的溶液，在τ⁻¹和某个临界速率γc之间观察到与普通缠结聚合物溶液类似的应力超调，而在γ > γc时观察到应变硬化。对于所有处于应变硬化状态的溶液，弹性固体的简单关系N₁/σ = γ（γ为剪切流施加的应变）成立。应变硬化归因于应变依赖的剪切模量，并用考虑网络链有限可扩展性的网络理论很好地描述。成功确定了网络链的段尺寸。因此，快速流动开始后获得的应力 - 应变关系对于表征网络性质很有用。
