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Viscosity characterization and flow simulation and visualization of polytetrafluoroethylene paste extrusion using a green and biofriendly lubricant |
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| Authors: | George A. Schmidt II Yu-Jyun Lin Yiyang Xu Dongfang Wang Galip Yilmaz Lih-Sheng Turng |
| Affiliation: | 1. Polymer Engineering Center, Department of Mechanical Engineering, University of Wisconsin–Madison, Madison, Wisconsin, USA Wisconsin Institute for Discovery, University of Wisconsin–Madison, Madison, Wisconsin, USA;2. Polymer Engineering Center, Department of Mechanical Engineering, University of Wisconsin–Madison, Madison, Wisconsin, USA Wisconsin Institute for Discovery, University of Wisconsin–Madison, Madison, Wisconsin, USA School of Mechanics and Engineering Science, Zhengzhou University, Zhengzhou, China National Center for International Research of Micro-Nano Molding Technology, Zhengzhou University, Zhengzhou, China;3. Polymer Engineering Center, Department of Mechanical Engineering, University of Wisconsin–Madison, Madison, Wisconsin, USA |
| Abstract: | Polytetrafluoroethylene (PTFE) and expanded PTFE (ePTFE) are ideal for various applications. Because PTFE does not flow, even when heated above its melting point, PTFE components are fabricated using a process called paste extrusion. This process entails blending PTFE powder particles with a lubricant to form PTFE paste, which is subsequently preformed, extruded, expanded (in the case of ePTFE), and sintered. In this study, ethanol was proposed as an alternative green lubricant for PTFE processing. Not only is ethanol benign and biofriendly, it provides excellent wettability and processing benefits. Using ethanol as a lubricant, the shear viscosity of PTFE paste and its flow behavior during paste extrusion were investigated. Frequency sweeps using a parallel-plate rheometer were performed on PTFE paste samples and various grits of sandpaper were used to reduce wall slip of PTFE paste. A viscosity model was generated and a multiphysics software was used to simulate PTFE paste extrusion. The simulated extrusion pressure was compared to experimental data of actual paste extrusion. Flow visualization experiments using colored PTFE layers were conducted to reveal the flow profile of the PTFE paste. The morphology of the expanded ePTFE tubes was examined using scanning electron microscopy and the effect of expansion ratio on ePTFE morphology was quantified. |
| Keywords: | expanded polytetrafluoroethylene (ePTFE) flow visualization green lubricant polytetrafluoroethylene (PTFE) viscosity characterization |