Technologies for Quality Improvement of the Injection Molded Polymer Products Utilizing the Heat Transfer Control Technique

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The main purpose of this research project is to develop the technologies for improvement of the quality of injection molded polymer products by utilizing the heat transfer control techniques, Which have been used only for maintaining the mold wall temperature uniform. The obtained results can be summarized into the followings:1. Phenomena occurring in the Packing-Holding Process and Control of Sink Mark Location by Controlling the Mold Wall Temperature Distribution. First of all, the phenomena occurring in the packing-holding process, which is used to be applied for reducing the sink mark generation, were investigated by means of visualization. And then, the control technique of the sink mark location by controlling the mold wall temperature distribution was examined under the packing-holding process. So as to apply the control technique for the practical molding, we tried to control the mold wall temperature distribution by changing the mold wall materials, which have the different thermal diffusivities, and the effectiveness of this method was confirmed.2.Rheological Examination of the Generation of Residual Stress and Molecular Orientation within the Injection Molded Polymer Products. The residual stress and molecular orientation are strongly affected both by the generation rate, i.e., cooling rate, and by their relaxation during the cooling process. In the injection molded polymer products, the generation of residual stress and molecular orientation shows complicated behaviors, because the cooling rate of the polymeric material varies in the thickness direction. From this point of view, generation process of the residual stress and molecular orientation was examined with the rheological approach. The results showed that the residual stress and molecular orientation frozen in the molded polymer can be controlled by controlling the cooling conditions through the molding processes.