Change in the critical nucleation radius and its impact on cell stability during polymeric foaming processes |
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Authors: | Siu N Leung Anson Wong Chul B Park |
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Affiliation: | a Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario, Canada M5S 3G8 b Department of Materials, Mechanical and Automation Engineering, Yanbian University of Science and Technology, Yanji, Jilin, People's Republic of China |
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Abstract: | The critical radius of cell nucleation is a function of the thermodynamic state that is uniquely determined by the system temperature, system pressure, and the dissolved gas concentration in the polymer/gas solution. Because these state variables change continuously during the foaming process, the critical radius varies simultaneously despite the traditional concept that it is a fixed thermodynamic property for a given initial state. According to classical nucleation theory, the critical radius determines the fate of the bubbles. Therefore, the change in the critical radius during foaming has a strong impact on the stability of foamed cells, especially in the production of microcellular or nanocellular foams. In this study, the continuous change in the critical radius is theoretically demonstrated under atmospheric pressure while bubbles are generated and expanded by the decomposition of a chemical blowing agent. The experimental results observed from the visualization cell are used to support the theoretically derived concept. Sustainability of the nucleated bubbles is also discussed by comparing the bubble size to the critical radius. |
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Keywords: | Bubble growth and collapse Diffusion Polymer foam Simulation Stability Visualization |
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