Effects of Pressure and Supercritical Fluid on Melt Viscosity of LDPE in Conventional and Microcellular Injection Molding

C.-L. Hsu; L.-S. Turng; T. A. Osswald; N. Rudolph; E. Dougherty; P. Gorton

doi:10.3139/217.2493

Article

Effects of Pressure and Supercritical Fluid on Melt Viscosity of LDPE in Conventional and Microcellular Injection Molding

, , , , and

Published/Copyright: April 6, 2013

Published by

Become an author with De Gruyter Brill

Submit Manuscript Author Information

From the journal International Polymer Processing Volume 27 Issue 1

Abstract

In this study, the flow and rheological behaviors of low density polyethylene (LDPE) and single-phase LDPE/N₂ polymer/gas solutions at various gas contents were measured using a high-pressure slit-die rheometer. The resulting rheology data of LDPE and LDPE/N₂ were curve fit using the Cross–WLF model to obtain the seven material model constants, which were then used in the simulation of conventional and microcellular injection molding processes. The pressure effect on the shear viscosity of LDPE was also studied. The pressure dependency coefficient, D3, in the Cross–WLF model was determined by the use of simulation to best fit the experimental results. In addition, a three-dimensional plot of shear viscosity as a function of shear rate and pressure at various temperatures was constructed. Based on this three-dimensional viscosity–shear rate–temperature–pressure plot, the increase in viscosity due to the pressure effect was found to be more profound at high pressures, low temperatures, and low shear rates.

^∗ Mail address: Lih-Sheng (Tom) Turng, University of Wisconsin – Madison, 1051 Mechanical Engineering Building, 1513 University Avenue, Madison, WI, 53706 USA. E-mail: turng@engr.wisc.edu

References

Amano, O., “Pressure Dependent Viscosity of Polymer Melts”, SPE ANTEC Tech. Papers, 504–511(2000)Search in Google Scholar

Chen, S., et al., “Measurement on Viscosity of Polystyrene Melts Dissolved with Supercritical Nitrogen Fluid during Microcellular Injection Molding”, SPE ANTEC Tech. Papers, 472–499(2009)Search in Google Scholar

Cheng, Y., “Thermodynamics of Phase Equilibrium Thermodynamics of Phase Equilibrium between Ethylene and Polyethylene”, Ph.D. Thesis, Texas Tech University, Lubbock(1976)Search in Google Scholar

Colton, J. S., Suh, N. P., “The Nucleation of Microcellular Thermoplastic Foam with Additives”, Polym. Eng. Sci., 27, 485–492(1987), DOI: http://dx.doi.org/10.1002/pen.760270702Search in Google Scholar

Han, C. D., Ma, C.Y., “Rheological Properties of Mixtures of Molten Polymer and Fluorocarbon Blowing Agent. 2. Mixtures of Low-Density Polyethylene and Fluorocarbon Blowing Agent”, J. Appl. Polym. Sci., 28, 831–850(1983), DOI: http://dx.doi.org/10.1002/app.1983.070280234Search in Google Scholar

Izu, P., et al., “Capillary and Slit-die Flow of Two Liquid-crystalline Polymers. The Effect of Pressure on Viscosity”, J. Polym. Sci. Part B Polym. Phys., 31, 347–356(1993), DOI: http://dx.doi.org/10.1002/polb.1993.090310313Search in Google Scholar

Klaiber, F., “Design, Construction and Analysis of a High Pressure Slit Rheometer”, Master Thesis, University of Wisconsin-Madison, Madison (2005)Search in Google Scholar

Kramschuster, A., et al., “Quantitative Study of Shrinkage and Warpage Behavior for Microcellular and Conventional Injection Molding”, Polym. Eng. Sci., 45, 1408–1418(2005), DOI: http://dx.doi.org/10.1002/pen.20410Search in Google Scholar

Kramschuster, A., et al., “Effect of Processing Conditions on Shrinkage and Warpage and Morphology of Injection Molded Parts Using Microcellular Injection Molding”, Plast. Rubber Compos.: Macromolecular Engineering, 35, 198–209(2006), DOI: http://dx.doi.org/10.1179/174328906X128199Search in Google Scholar

Kwag, C., et al., “Rheology of Molten Polystyrene with Dissolved Supercritical and Near-critical Gases”, J. Polym. Sci., Part B: Polym. Phys., 37, 2771–2781(1999), DOI: http://dx.doi.org/10.1002/(SICI)1099-0488(19991001)37:19<2771::AID-POLB6>3.0.CO;2-9Search in Google Scholar

Lee, J. J., Cha, S. W., “Characteristics of the Skin Layers of Microcellular Injection Molded Parts”, Polym. Plast. Technol. Eng., 45, 871–877(2006), DOI: http://dx.doi.org/10.1080/03602550600611768Search in Google Scholar

Lee, M., et al., “Extrusion of PE/PS blends with Supercritical Carbon Dioxide”, Polym. Eng. Sci., 38, 1112–1120(1998), DOI: http://dx.doi.org/10.1002/pen.10278Search in Google Scholar

Lee, M., “Extrusion of Polymers and Polymer Blends with Supercritical Carbon Dioxide”, Ph.D. Thesis, University of Waterloo, Waterloo, Canada(1999a)Search in Google Scholar

Lee, M., et al., “Measurements and Modeling of PS/Supercritical CO₂ Solution Viscosities”, Polym. Eng. Sci., 39, 99–109(1999b)10.1002/pen.11400Search in Google Scholar

Marcilla, A., Beltrán, M.: Chapter 5 Mechanisms of Plasticizers Action, Handbook of Plasticizers, ChemTec Publishing, Toronto, Canada(2004)Search in Google Scholar

Nobelen, M., et al., “Modeling of the Rheological Behavior of Polyethylene/Supercritical Formula Not Shown Solutions”, Chem. Eng. Sci., 61, 5334–5345(2006), DOI: http://dx.doi.org/10.1016/j.ces.2006.03.052Search in Google Scholar

Royer, J. R., et al., “High-pressure Rheology of Polystyrene Melts Plasticized with CO_2: Experimental Measurement and Predictive Scaling Relationships”, J. Polym. Sci. Part B: Polym. Phys., 38, 3168–3180(2000), DOI: http://dx.doi.org/10.1002/1099-0488(20001201)38:23<3168::AID-POLB170>3.0.CO;2-ESearch in Google Scholar

Trexel Inc., “Injection Overview,” http://trexel.com/injection-molding-solutions/index.php(2011)Search in Google Scholar

Wang, J., Park, C. B., “Pressure Profile in Annular Die Using PP/CO₂ Solution Viscosity”, SPE ANTEC Tech. Papers, 896–902(2006)Search in Google Scholar

Received: 2011-03-17

Accepted: 2011-09-11

Published Online: 2013-04-06

Published in Print: 2012-03-01

You are currently not able to access this content.

Articles in the same Issue

https://doi.org/10.3139/217.2493