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Automotive Interior Injection Molded Parts Using Microcellular Foaming Technology
ISSN: 0148-7191, e-ISSN: 2688-3627
Published September 30, 2014 by SAE International in United States
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The microcellular foam injection molding process for thermoplastic materials provides design flexibility and cost savings opportunities not found in conventional injection molding. This process allows for plastic part design with material wall thickness optimized for functionality.
The combination of density reduction and design for functionality can result in material and weight savings of up to 20%. With the correct equipment configuration, mold design, and processing conditions, these microcellular voids are uniform in size and distribution. The use of microcellular foam molding provides significant reductions in cycle time, material consumption, injection pressure, and clamp tonnage.
In this work, a physical foam molding process, MuCell, is applied to a polypropylene (PP) composite. The MuCell injection molding process involves the highly controlled use of gas in supercritical state, as the physical blowing agent, to create millions of micron-sized voids in thin wall molded parts (less than 3mm).
The results show that a weight reduction can be achieved without significant degradation in mechanical properties, such as stiffness and impact resistance. MuCell also contributes to faster cooling from the melt as well as the elimination of pack and hold phase, which both result in shorter injection molding cycle times and reduced warpage.
Once material tests have been completed, final part tests will also be performed, to validate established design specifications. These results presented here indicate that microcellular foam molding technology has good potential to be applied to interior parts of vehicles, contributing to weight reduction and productivity increase.
CitationHarris, A., Lee, E., Peraro, W., Nunes, S. et al., "Automotive Interior Injection Molded Parts Using Microcellular Foaming Technology," SAE Technical Paper 2014-36-0172, 2014, https://doi.org/10.4271/2014-36-0172.
- Edited by: Kemmere, M. and Meyer, T., “Supercritical Carbon Dioxide in Polymer Reaction Engineering,” Wiley-VCH, 2005, ISBN: 978-3-527-31092-0.
- Berry, M., “Applied Plastics Engineering Handbook,” Elsevier Inc., 215-226, 2011.
- Fu, S.-Y., Lauke, B., Mader, E., Yue, C.-Y. et al., “Tensile properties of short-glass-fiber- and short-carbon-fiber-reinforced polypropylene composites,” Composites: Part A 31: 1117-1125, 2000.
- Kazarian, S. G., “Polymer Processing with Supercritical Fluids,” Polymer Science 42(1):78-101, 2000.
- Kramschuster, A., Cavitt, R., Ermer, D., Chen, Z. et. al, “Quantitative Study of Shrinkage and Warpage Behavior for Microcellular and Conventional Injection Molding,” Polymer Engineering and Science 45: 1408-1418, 2005.
- Lee, L.J., Zeng, C., Cao, X., Han, X. et al., “Polymer nanocomposite foams,” Composites Science and Technology 65: 2344-2363, 2005.
- Lin, Chaur-Kie, “Study on Mechanical Properties of ABS Parts in Microcellular Injection Molding Process,” ANTEC 708-712, 2005.
- Naito, Y., Mizoguchi, K., Terada, K., and Kamiya, Y., “The Effect of Pressure on Gas Permeation through Semicrystalline Polymers above the Glass Transition Temperature,” J. Polym. Sci., Part B: Polym. Phys. 29: 457-462, 1991.
- Naitove, M., “New Light on How to Optimize Properties of Microcellular Foams,” Plastics Technology, Sep. 2008.
- Nalawade, S., Picchioni, F., and Janssen, L. P. B. M., “Supercritical carbon dioxide as a green solvent for processing polymer melts: Processing aspects and applications,” 31: 19-43, 2006.
- Rodriguez-Perez, M. A., Ruiz-Herrero, J.L., Solorzano, E., and Saja, J.A., “Gas Diffusion in Polyolefin Foams During Creep Tests. Effect on Impact Behavior and Recovery After Creep,” Cellular Polymers 25(4):221-236, 2006.
- Ruiz, J.A.R., Pedros, M., Tallon, J-M., and Dumon, M., “Micro and nano cellular amorphous polymers (PMMA, PS) in supercritical CO2 assisted by nanostructured CO2-philic block copolymers - One step foaming process,” J. of Supercritical Fluids 58: 168-176, 2011.
- Wong, S., Lee, J. W. S., Naguib, H. E., and Park, C. B., “Effect of Processing Parameters on the Mechanical Properties of Injection Molded Thermoplastic Polyolefin (TPO) Cellular Foams,” Macromolecular Materials and Engineering 293:605-613, 2008, doi:10.1002/mame.200700362.
- Sawyer, L.C., “Determination of Fiberglass lengths: Sample Preparation and Automatic Image Analysis,” Polymer Engineering and Science 19(5): 377-382, 1979.
- Trexel Newsletter, MuCell Process Notes, “Trexel Introduces New Long Glass Fiber Screw Design for MuCell Process Which Improves Fiber Length Retention,” Volume XV, 2007.
- Xu, J., “Process of Long Glass Fiber Reinforced Thermoplastics for Microcellular Injection Molding,” Plastics Engineering, Mar. 2008.