Wu Wangqing, Zeng Ke, Zhao Baishun, Duan Fengnan, Jiang Fengze
State Key Laboratory of High-Performance Complex Manufacturing, School of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China.
Institute of Polymer Technology, Friedrich Alexander University Erlangen Nurnberg, Weichselgarten 9, D-91058 Erlangen, Germany.
Polymers (Basel). 2021 Dec 18;13(24):4451. doi: 10.3390/polym13244451.
Capillary rheometers have been widely used for the rheological measurement of polymer melts. However, when micro capillary dies are used, the results are usually neither accurate nor consistent, even under the same measurement conditions. In this work, theoretical modeling and experimental studies were conducted for a more profound understanding of the mechanism by which the initial and boundary conditions influence the inaccuracy in the apparent shear viscosity determination with micro capillary dies (diameters: 500 μm, 200 μm, 100 μm). The results indicate that the amount of polymer initially in the barrel, the pre-compaction pressure and the capillary die diameter have a significant influence on the development of the micro scale inlet pressure, which directly determines the accuracy of the measurement at low and medium shear rates. The varying melt compressibility was confirmed to be the main factor directly related to the inaccuracy in the micro scale apparent shear viscosity determination. It is suggested that measures such as reducing the amount of polymer initially in the barrel and increasing the pre-compaction pressure could be used to reduce the measurement inaccuracy.
毛细管流变仪已被广泛用于聚合物熔体的流变学测量。然而，当使用微毛细管模头时，即使在相同的测量条件下，结果通常也不准确且不一致。在这项工作中，进行了理论建模和实验研究，以更深入地了解初始条件和边界条件影响使用微毛细管模头（直径：500μm、200μm、100μm）测定表观剪切粘度时的不准确性的机制。结果表明，料筒中初始聚合物量、预压实压力和毛细管模头直径对微尺度入口压力的发展有显著影响，而微尺度入口压力直接决定了中低剪切速率下测量的准确性。已证实熔体可压缩性的变化是与微尺度表观剪切粘度测定中的不准确性直接相关的主要因素。建议采取减少料筒中初始聚合物量和增加预压实压力等措施来降低测量误差。
