• Proceedings of the KSME Conference
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• 2001.06c
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• pp.621-626
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• 2001

Microcellular foaming process was developed at MIT in 1980's to save a quantity of raw materials and improve mechanical properties. There are many process variables in appling microcellular foaming process to the conventional injection molding process. Of all process variables, part dimension control and shrinkage are the most influential on the post molded dimension. The post molding dimensional change of thermoplastic resins is important to tool designers for predicting the specific difference of molded part vs. actual mold cavity. Generally, articles injection molded are smaller in size than the cavity; hence, the term shrinkage factor is used to define the allowance a designer specifies. It is important to consider the factors that influence molded part dimension. According to ASTM Designation: D 955, shrinkage from mold dimensions of molded plastics was measured. In injection molding, the difference between the dimensions of the mold and of the molded article produced therein from a given material may vary according to the design and operation of the mold. In this paper, shrinkage data of molded plastic parts was obtained. It can be an important information for designing optimum mold system in a microcellular foaming injection molding process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1630-1635
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• 2005

The microstructure of the parts made by the microcellular injection molding process influence properties, including impact strength, tensile strength and density of material. Microstructure of microcellular plastics is divided into core foaming region and solid skin region. Core foaming region is influenced by pressure drop rate, viscosity and cell coalescence. However, actual mechanism of the skin layers is not known despite its importance. The study on the skin layer is getting important because foaming rate of the plastics is determined by the thickness ratio of the skin layer. Especially in case of large molded part, control of the skin layer is needed because skin layer thickness is changed largely. Therefore it is necessary to study variation in skin layer thickness with processing parameters. In this paper, the influence of temperatures in the mold cavity on the skin layer s thickness was also addressed. In addition, the relationship between the temperature distributions across cavity of the mold with impact strength on parts made with the microcellular injection molding process was addressed. In addition, the method to predict the variation in skin layer thickness with mold temperature is discussed.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.263-268
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• 2001

MCPs means Micro Cellular Plastics. The micro-cells are generated in the products by the difference of dissolution through the pressure drop after super critical fluid of CO2 or N2 dissolves into polymer. We have developed injection molding process adopting MCPs and applied it to a broad range of injection molded thermoplastic materials and applications. It can prevent the leakage of impact strength and increase the thermal conductivity, moreover regulate the thermal conductivity. Then we can develop the high strength foaming plastics. Also, it can be gained a competitive advantage by utilizing its processing benefits, e.g. the lightweight products and significant reductions in material consumption.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1406-1409
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• 2003

There is a great demand for reducing the amount of material used in mass-produced plastics parts, for material cost constitutes a large percentage of the total cost of 60%. It may be noted that the price of plastics is directly rotated to the price of petroleum. Material reduction therefore decreases the amount of oil needed for the manufacture of plastics and thus help conserve this natural resource. Therefore microcellular foaming process(MCPs) was studied for solving this problems alternatively in 1980's at M.I.T Until now in MCPs carbon dioxide gas was mainly used for microcellular foaming. Besides, Talc was used for reducing the price of plastics. Consequently, we must certificate using the Talc in MCPs according to contents of the Talc.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.3
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• pp.108-113
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• 2000

An important process for making a new class of polymeric material is called microcellular plastics invented at the Massachusetts Institute of Technology. Many researches for microcellular plastics have been done in various ways and fields. But a research for the polymer which has previous history has not been tried yet. In this paper, weight gain of $CO_2$ was measured in a polymer matrix which had previous history and no history. In each case, experimental data for solubility and diffusivity was shown. A model for $CO_2$ solution process in molecular range was made. The conclusion of this paper is that the previous history has an effect on diffusivity but not solubility and the previous history made by $CO_2$ in supercritical state makes diffusivity of $CO_2$ larger.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.725-726
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• 2012

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.759-760
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• 2009

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.827-828
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• 2008

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.10a
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• pp.403-404
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• 2009

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.585-590
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• 1997

Conventional foaming process has defects such as lower mechanical properties than ur~foaming material due to non-uniform cell distribution and environmental pollution problem caused by chemical blowing agency. So, a new foaming process such as Microcelluar plastics has been introduced to use inactive gases as a foaming agency. In order to apply Microcellular plastics for mass production process system such as extrusion, injection molding and blow molding, it needs to predict the change in material properties of polymer according to the amount of meltingas. In Polymer molding applying Microcelluar plastics, the change of viscosity among several material properties is the most important factor. Therefore, this paper is aimed to establish the method which not only finds out but also predicts the change of viscosity of ABS(Acrylonitri1e Butadiene Styrene) resin according to inert gas amount in extrusion molding.