• Polymer(Korea)
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• v.36 no.1
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• pp.34-40
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• 2012

The foaming of poly(butylene succinate) (PBS) using supercritical $CO_2(scCO_2)$ was studied. In order to improve the melt strength, PBS was modified using the reactive compounding technique. Rapid decompression of $scCO_2$-saturated PBS at a temperature above the depressed $T_m$ yielded expanded microcellular foams. The resulting foam structure could be controlled by manipulating process conditions. Experiments varying the foaming temperature while holding other variables constant showed that higher temperatures produced larger cells and reduced cell densities. Higher saturated pressures led to higher nucleation densities and smaller cell sizes. Decreasing the rate of depressurization permitted a longer period of cell growth and therefore larger cells were obtained.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.4 s.175
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• pp.824-829
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• 2000

The industries use polymer materials for many purposes because they have many merits. But these materials' costs take up too much proportion in overall cost of products that use these materials as their major material. So it is very economical for polymer industries to reduce these costs. Microcellular foaming process appeared in 1980's to solve this problem and it proved to be quite successful. This process uses inert gases such as CO2, N2. As these gases are dissolved into polymer matrices. many properties are changed. Glass transition temperature is one of these properties. DSC, DMA are devices that measures this temperature, but these are not sufficient to measure the temperature of polymer containing gas. In this paper, we devised a new tester that uses magnetism. We used this device to acquire data of the change of glass transition temperature and made Cha-Yoon model that can predict the change of glass transition temperature. Using this model, the change of this temperature can be estimated as a function of weight gain of gas. Cha-Yoon model proved that Chow's model is inappropriate to predict the change of glass transition temperature of polymer matrices containing gas.

• Polymer(Korea)
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• v.37 no.6
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• pp.685-693
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• 2013

The foams of a poly(lactic acid) modified by the reactive compounding were produced with the batch foaming technique using supercritical $CO_2(scCO_2)$. Experiments were performed at $105{\sim}135^{\circ}C$ and 12~24 MPa. The blowing ratio and foam structure were significantly affected by changing the temperature and pressure conditions in the foaming process. The blowing ratio first increased with increasing foaming temperature and saturation pressure, reached a maximum and then decreased with a further increase in the foaming temperature and saturation pressure. Decreasing the rate of depressurization permitted a longer period of cell growth and therefore larger microcellular structures were obtained.