Sousa Patrícia C, Vega Emilio J, Sousa Renato G, Montanero José M, Alves Manuel A
1Departamento de Engenharia Química, CEFT, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal.
2Departamento de Ingeniería Mecánica, Energética y de los Materiales and Instituto de Computación Científica Avanzada (ICCAEx), Universidad de Extremadura, E-06006 Badajoz, Spain.
Rheol Acta. 2017;56(1):11-20. doi: 10.1007/s00397-016-0980-1. Epub 2016 Nov 19.
The characterization of the extensional rheology of polymeric solutions is important in several applications and industrial processes. Filament stretching and capillary breakup rheometers have been developed to characterize the extensional properties of polymeric solutions, mostly for high-viscosity fluids. However, for low concentration polymer solutions, the measurements are difficult using available devices, in terms of the minimum viscosity and relaxation times that can be measured accurately. In addition, when the slow retraction method is used, solvent evaporation can affect the measurements for volatile solvents. In this work, a new setup was tested for filament breakup experiments using the slow retraction method, high-speed imaging techniques, and an immiscible oil bath to reduce solvent evaporation and facilitate particle tracking in the thinning filament. Extensional relaxation times above around 100 μs were measured with the device for dilute and semi-dilute polymer solutions. Particle tracking velocimetry was also used to measure the velocity in the filament and the corresponding elongation rate, and to compare with the values obtained from the measured exponential decay of the filament diameter.
聚合物溶液拉伸流变学的表征在多个应用和工业过程中都很重要。已经开发出细丝拉伸流变仪和毛细管破裂流变仪来表征聚合物溶液的拉伸性能，主要用于高粘度流体。然而，对于低浓度聚合物溶液，就可精确测量的最小粘度和松弛时间而言，使用现有设备进行测量很困难。此外，当使用缓慢回缩法时，溶剂蒸发会影响挥发性溶剂的测量。在这项工作中，测试了一种新装置，用于使用缓慢回缩法、高速成像技术和不混溶油浴进行细丝破裂实验，以减少溶剂蒸发并便于在变细的细丝中进行颗粒跟踪。使用该装置对稀聚合物溶液和半稀聚合物溶液测量得到了高于约100微秒的拉伸松弛时间。粒子跟踪测速技术还用于测量细丝中的速度和相应的伸长率，并与从测量的细丝直径指数衰减获得的值进行比较。
