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Licensed Unlicensed Requires Authentication Published by De Gruyter April 6, 2013

Study of Microcellular Injection Molding with Expandable Thermoplastic Microsphere

J. Peng, E. Yu, X. Sun, L.-S. Turng and X.-F. Peng


Injection molding with expandable thermoplastic microspheres (ETM) containing blowing chemicals is capable of fabricating lightweight, dimensionally stable plastic parts while using less material. This paper presents the study of microcellular injection molding of low density polyethylene (LDPE), polypropylene (PP), and polystyrene (PS) parts with various ETM contents. It was found that the molded parts exhibit relatively better surface quality than conventional foamed parts. The microcellular morphology and cell density of the fractured cross-sectional surfaces were characterized using a scanning electron microscope (SEM). As reflected by the testing results, the cell microstructure – such as cell size, cell density, and a layered structure with a foamed core sandwiched by skin layers – play an important role in the weight reduction, surface quality, and mechanical properties. A smaller cell diameter and a thicker skin layer help to improve the surface quality and tensile properties of the injection molded parts with ETM. Finally, an appropriate ETM content has a positive effect on cell microstructure and weight reduction, whereas too high a concentration of microspheres adversely affects the tensile properties and surface quality.

Mail address: Lih-Sheng Turng, University of Wisconsin-Madison, 1513 University Avenue, Madison, WI, 53706 USA. E-mail:


Chen, S. C., et al., “Passive Mold Temperature Control By a Hybrid Filming Microcellular Injection Molding Processing”, Int. Comm. He., 35, 822827(2008), DOI: 10.1016/j.icheatmasstransfer.2008.03.013Search in Google Scholar

Chen, S. C., et al., “Rapid Mold Temperature Variation for Assisting the Micro Injection of High Aspect Ratio Micro-feature Parts Using Induction Heating Technology”, J. Microm. M., 16, 17831791(2006), DOI: 10.1088/0960-1317/16/9/005Search in Google Scholar

Kramschuster, A., et al., “Injection Molded Solid and Microcellular Polylactide and Polylactide Nanocomposites”, J. Biobased Mater. Bio., 1, 3745(2007), DOI: 10.1166/jbmb.2007.004Search in Google Scholar

Kwang, C., et al., “Effects of Dissolved Gas on Viscoelastic Scaling and Glass Transition Temperature of Polystyrene Melts”, Ind. Eng. C. R., 40, 30483052(2001), DOI: 10.1021/ie000680eSearch in Google Scholar

Lee, J., et al., “A Novel Method for Improving the Surface Quality of Microcellular Injection Molded Parts”, Polymer, 52, 14361446(2011)10.1016/j.polymer.2011.01.026Search in Google Scholar

Lee, J., Turng, L. S., “Improving Surface Quality of Microcellular Injection Molded Parts through Mold Surface Temperature Manipulation with Thin Film Insulation”, Polym. Eng. Sci., 50, 12811289(2010), DOI: 10.1002/pen.21658Search in Google Scholar

Naguib, H. E., et al., “Strategies for Achieving Ultra Low Density Polypropylene Foams”, Polym. Eng. Sci., 41, 14811492(2002), DOI: 10.1002/pen.11045Search in Google Scholar

Pilla, S., et al., “Solid and Microcellular Polylactide-Carbon Nanotube Nanocomposites”, Int. Polym. Proc., 22, 418428(2007)Search in Google Scholar

Turng, L. S., Kharbas, H.Development of a Hybrid Solid Microcellular Co-injection Molding Process,” Int. Polym. Proc., 19, 7786(2004)Search in Google Scholar

Yoon, J. D., et al., “A Mold Surface Treatment For Improving Surface Finish of Injection Molded Microcellular Parts”, Cell. Polym., 23, 3947(2004)Search in Google Scholar

Yuan, al., “Spatial Orientation of Nanoclay and Crystallite in Microcellular Injection Molded Polyamide-6 Nanocomposites”, Polym. Eng. Sci., 47, 765779(2007), DOI: 10.1002/pen.20752Search in Google Scholar

Received: 2010-10-24
Accepted: 2011-03-04
Published Online: 2013-04-06
Published in Print: 2011-07-01

© 2011, Carl Hanser Verlag, Munich