Study on Quality Improvement Techniques for Injection-Molding of Polymer Utilizing Heat Transfer Control

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In this study, radiation heating of the polymeric materials was investigated as the active controlling technique for cooling of moldedpolymer within the mold. In order to obstruct the cooling of polymer melt injected into the cold mold cavity, polymer melt in the cavity was heated by using CO2 laser during the filling stage of the injection-molding process, and the effects of radiation heating on the quality of molded polymer was experimentally examined. The results can be summarized as follows :(1) Quality Improvement due to Radiation Heating : Radiation heating technique was adoptedto produce a polystirene strip, and the quality of molded polymer was investigated. The obstruction of cooling due to radiation heating results in reducing the failures originated from solidification of polymer melt during the filling stage, such as residual birefringence frozen in surface region of molded strip, short-shot due to increasing the viscosity of polymer melt, lowering the transcribability of strip surface, etc.(2) Temperature Profiles in the Polymer Irradiatedby InfraredLaser : Temperatureprofile within the polymer melt irradiatedby infraredradiation is determinedby the relation between radiation absorption within the polymer and conductive cooling due to contact with the cold mold wall. In order to obtain the understandings about the temperature profiles under the irradiation condition, heat transfer within the polymer was numerically examined. The results showed that the temperature within the molded polymer is strongly affected by the relation between the monochromatic absorption coefficient of polymer material and wavelength distribution of the heating infraredradiation, and that, under the realistic condition, heating effect due to infraredradiation penetrates about 0.5-1mm from the polymer surface.