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Licensed Unlicensed Requires Authentication Published by De Gruyter November 3, 2015

Paste Extrusion and Mechanical Properties of PTFE

M. Ansari, D. Vavlekas, J. L. McCoy and S. G. Hatzikiriakos

Abstract

The paste extrusion process of two types of PTFE has been studied in capillary extrusion using dies having different reduction ratio (RR) and die entrance angles. The extrusion pressure shows a weak increase with shear rate over a wide range of flow rates and a more significant increase with reduction ratio. Moreover, the extrusion pressure exhibits a minimum for entrance angle at around 30°. A simple analytical model based on the radial flow hypothesis (previously developed) has been found to represent the extrusion pressure adequately as a function of flow rate (shear rate) and geometrical characteristics of the capillary dies. The extrudates collected at different processing conditions were dried and tested in uniaxial extension to assess their effect on mechanical properties. The tensile modulus, yield stress and ultimate tensile strength of the obtained extrudates were found to be increasing functions of reduction ratio, although the opposite effect was found for the ultimate elongational strain. These mechanical properties are also found to be insensitive to changes in the die entrance angle although the ultimate tensile strength has shown a maximum at the entrance angle of about 60°. The PTFE paste extrudates show a Poisson's ratio equal to zero in tensile experiments, thus exhibiting expansion (significant density reduction with stretching). Finally, a simple model was derived for the density change in tensile deformation by taking into the account the Poisson's ratio and the strain recovery (recovery of the elastic energy stored upon removal of the tensile stress).


* Mail address: Savvas G. Hatzikiriakos, Chemical and Biological Engineering Department, The University of British Columbia, Vancouver, BC, Canada, V6T 1Z3, E-mail:

References

Ardakani, H. A., Mitsoulis, E. and Hatzikiriakos, S. G., “A Simple Improved Mathematical Model for Polytetrafluoroethylene (PTFE) Paste Extrusion”, Chem. Eng. Sci., 89, 216222 (2013a) 10.1016/j.ces.2012.11.040Search in Google Scholar

Ardakani, H. A., Mitsoulis, E. and Hatzikiriakos, S. G., “Polytetrafluoroethylene Paste Extrusion: A Fibrillation Model and its Relation to Mechanical Properties”, Int. Polym. Proc., 28, 306313 (2013b) 10.3139/217.2744Search in Google Scholar

Ariawan, A. B., Ebnesajjad, S. and Hatzikiriakos, S. G., “Paste Extrusion of Polytetrafluoroethylene (PTFE) Fine Powder Resins”, Can. Chem. Eng. J., 80, 11531165 (2002a) 10.1002/cjce.5450800617Search in Google Scholar

Ariawan, A. B., Ebnesajjad, S. and Hatzikiriakos, S. G., “Preforming Behavior of Polytetrafluoroethylene Paste”, Powder Technology, 121, 249258 (2001) 10.1016/S0032-5910(01)00385-0Search in Google Scholar

Ariawan, A. B., Ebnesajjad, S. and Hatzikiriakos, S. G., “Properties of Polytetrafluoroethylene (PTFE) Paste Extrudates”, Polym. Eng. Sci., 42, 12471259 (2002b) 10.1002/pen.11028Search in Google Scholar

Caddock, B. D., Evans, K. E., “Microporous Materials with Negative Poisson's Ratios: I. Microstructure and Mechanical Properties”, J. Phys. D: Appl. Phys., 22, 18771882 (1989) 10.1088/0022-3727/22/12/012Search in Google Scholar

Choi, K. J., Spruiell, J., “Structure Development in Multistage Stretching of PTFE Films,”J. Polym. Sci. Part B: Polym. Phys., 48,22482256 (2010) 10.1002/polb.22107Search in Google Scholar

Dealy, J. M., Wissbrun, K. F.: Melt Rheology and its Role in Plastics Processing Theory and Applications, Van Nostrand Reinhold, New York (1990) 10.1007/978-1-4615-9738-4Search in Google Scholar

Ebnesajjad, S.: Fluoroplastics, Non-Melt Processible Fluoroplastics, Vol. 1, Plastics Design Library, William Andrew Corp., New York (2000)Search in Google Scholar

Gore, W. L., U.S. Patent 3 953 566 (1976)Search in Google Scholar

Guo, Y. H., Chen, J. H., Gao, J. X., Zhang, H. P. and Feng, X. X., “A Study on the Nonuniform Deformation of PTFE Membrane during its Tentering Transverse Stretching”, J. Appl. Polym. Sci., 116, 11241130 (2010)Search in Google Scholar

Haw, M. D., “Jamming, Two-Fluid Behavior, and Self-Filtration in Concentrated Particulate Suspensions”, Phys. Rev. Lett., 92, 18506185509 (2004) 10.1103/PhysRevLett.92.185506Search in Google Scholar

Horrobin, D. J., Nedderman, R. M., “Die Entry Pressure Drops in Paste Extrusion”, Chem. Eng. Sci., 53, 32153225 (1998) 10.1016/S0009-2509(98)00105-5Search in Google Scholar

Huang, L. T., Hsu, P. S., Kuo, C. Y., Chena, C. S. and Lai, J. Y., “Pore Size Control of PTFE Membranes by Stretch Operation with Asymmetric Heating System”, Desalination, 233, 6472 (2008) 10.1016/j.desal.2007.09.028Search in Google Scholar

Kitamura, T., Kurumada, K. I., Tanigaki, M., Ohshima, M. and Kanazawa, S. I., “Formation Mechanism of Porous Structure in Polytetrafluoroethylene (PTFE) Porous Membrane through Mechanical Operations”, Polym. Eng. Sci., 39, 22562263 (1999) 10.1002/pen.11613Search in Google Scholar

Kurumada, K., Kitamura, T., Fukumoto, N., Oshima, M., Tanigaki, M. and Kanazawa, S., “Structure Generation in PTFE Porous Membranes induced by the Uniaxial and Biaxial Stretching Operations”, J. Membr. Sci., 149, 5157 (1998) 10.1016/S0376-7388(98)00179-3Search in Google Scholar

Lalia, B. S., Kochkodan, V., Hashaikeh, R. and Hilal, N., “A Review on Membrane Fabrication: Structure, Properties and Performance Relationship”, Desalination, 326, 7795, (2013) 10.1016/j.desal.2013.06.016Search in Google Scholar

Mazur, S.: “Chapter 15 Paste Extrusion of Poly(tetrafluoroethylene) Fine Powders”, in Polymer Powder Technology, Narkis, P. M., Rosenzweig, N. (Eds.), John Wiley and Sons, New York, p. 441481 (1995)Search in Google Scholar

O'Leary, K., Geil, P. H., “Polytetrafluoroethylene Fibril Structure”, J. Appl. Phys., 38, 41694181 (1967) 10.1063/1.1709101Search in Google Scholar

Ochoa, I., Hatzikiriakos, S. G., “PTFE Paste Preforming: Viscosity and Surface Tension Effects”, Powder Technol., 146, 7383 (2004) 10.1016/j.powtec.2004.06.003Search in Google Scholar

Ochoa, I., Hatzikiriakos, S. G., “Paste Extrusion of PTFE: Surface Tension and Viscosity Effects”, Powder Technol., 153, 108118 (2005) 10.1016/j.powtec.2005.02.007Search in Google Scholar

Ochoa, I., Hatzikiriakos, S. G. and Mitsoulis, E., “Paste Extrusion of Polytetrafluoroethylene (PTFE): Temperature, Blending and Processing Aid Effects”, Int. Polym. Proc., 21, 497503 (2006) 10.3139/217.0028Search in Google Scholar

Ranjbarzadeh-Dibazar, A., Shokrollahi, P., Barzin, J. and Rahimi, A., “Lubricant Facilitated Thermo-Mechanical Stretching of PTFE and Morphology of the Resulting Membranes,”J. Membr. Sci., 470, 458469 (2014) 10.1016/j.memsci.2014.07.062Search in Google Scholar

Snelling, G. R., Lontz, J. F., “Mechanism of Lubricant-Extrusion of Teflon TFE-Tetrafluoroethylene Resins”, J. Appl. Polym. Sci., 3, 257265 (1960) 10.1002/app.1960.070030901Search in Google Scholar

Sperati, C. A., “Physical Constants of Fluoropolymers”, in Polymer Handbook, Brandrup, J., Immergut, E. H. (Eds.), John Wiley and Sons, New York, p.V35V56 (1989)Search in Google Scholar

Wang, H., Ding, S., Zhu, H., Wang, F., Gu, Y., Zhang, H. and Chen, J., “Effect of Stretching Ratio and Heating Temperature on Structure and Performance of PTFE Hollow Fiber Membrane in VMD for RO Brine”, Sep. Purif. Technol., 126, 8294 (2014) 10.1016/j.seppur.2014.02.027Search in Google Scholar

Received: 2015-06-02
Accepted: 2015-08-13
Published Online: 2015-11-03
Published in Print: 2015-11-30

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