论文标题
聚合物溶液稀疏中的粘弹性状态过渡
Transition to the viscoelastic regime in the thinning of polymer solutions
论文作者
论文摘要
在这项研究中，我们研究了牛顿溶液的捏合期间牛顿和粘弹性方案之间的过渡，并讨论了其与线圈 - 拉伸过渡的联系。从喷嘴中脱落的脱落与液体的形成有关，这会导致消失的小区域中局部应力的差异。如果液体是聚合物溶液，则增加应力会逐渐放松聚合物链，直到粘度的增加会大大减慢稀疏。对粘弹性行为的阈值对应于宏观应变率$ \ dot {\ varepsilon} _ {\ rm c} $。在本研究中，我们表征了$ \ dot {\ varepsilon} _ {\ rm c} $相对于聚合物浓度和摩尔重量，溶剂粘度，以及喷嘴大小，即滴的重量。我们为这些变化提供经验缩放定律。我们还分析了过渡时的变薄动力学，并表明它遵循由时间尺度$ {\ dot {\ varepsilon} _ {\ rm c}}}^{ - 1} $控制的自相似动力学。这个特征时间与聚合物的放松时间不同，总是短。
In this study, we investigate the transition between the Newtonian and the viscoelastic regimes during the pinch-off of droplets of dilute polymer solutions and discuss its link to the coil-stretch transition. The detachment of a drop from a nozzle is associated with the formation of a liquid neck that causes the divergence of the local stress in a vanishingly small region. If the liquid is a polymer solution, this increasing stress progressively unwinds the polymer chains, up to a point where the resulting increase in the viscosity slows down drastically the thinning. This threshold to a viscoelastic behavior corresponds to a macroscopic strain rate $\dot{\varepsilon}_{\rm c}$. In the present study, we characterize the variations of $\dot{\varepsilon}_{\rm c}$ with respect to the polymer concentration and molar weight, to the solvent viscosity, and to the nozzle size, i.e., the weight of the drop. We provide empirical scaling laws for these variations. We also analyze the thinning dynamics at the transition and show that it follows a self-similar dynamics controlled by the time scale ${\dot{\varepsilon}_{\rm c}}^{-1}$. This characteristic time is different and always shorter than the relaxation time of the polymer.
