| Co-Investigator(Kenkyū-buntansha) |
SATO Yoshiyuki Hiroshima University, Faculty of Engineering, Research Associate, 工学部, 助手 (50243598)
MASUOKA Hirokatsu Hiroshima University, Faculty of Engineering, Professor, 工学部, 教授 (50034385)
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| Budget Amount *help |
¥14,200,000 (Direct Cost: ¥14,200,000)
Fiscal Year 1999: ¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 1998: ¥11,000,000 (Direct Cost: ¥11,000,000)
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| Research Abstract |
Microcellular plastics (MP) is a newly innovated foam plastic material that includes numerous cells of very small sizes in it. This material has many advantages over conventional foam plastics, such as superior thermal, mechanical and electrical properties, as well as environmentally accepted production process and product because of using benign gases such as carbon dioxide and nitrogen.
In this study the effects of saturation pressure, saturation temperature, decompression rate, time to start heating, heating temperature and heating time on the cell structure (average cell diameter, number density of cells and expansion ratio) were studied in batch-wise production of foam polystyrene using carbon dioxide and nitrogen as blowing agents. The experiments were carried out mainly at high temperatures above the glass transition temperature of the polymer where industrial production processes are operated. This work proposed a "quick heating" method, in which dissolution, decompression and heating processes are performed continuously in a high-pressure chamber. This new method could utilize the dissolved gas for foaming effectively and control the cell structure widely. As a result, it was found that increasing pressure (gas solubility) increases number density of cells and decreases average cell diameter, that the effect of increasing temperature is different for different gases, that increasing decompression rate increases the nucleation rate of cells, that short interval between decompression and heating processes results in the larger cell diameter, and that heating at high temperatures first increases cell diameter but decreases it later. Furthermore, the relationship between process conditions and cell structure was expressed qualitatively by extending classical nucleation theory and cell growth theory and by considering various properties of the polymer - gas mixture accurately.
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