BLOW MOLDING OF SYNTHETIC RESIN USING HEAT INSULATING LAYER-COATED MOLD - EFFECT OF HEAT INSULATING LAYER CHARACTERISTICS ON IMPROVEMENT OFTRANSFERABILITY OF THE MOLDED ARTICLE

Improvement of surface transferability of an blow-molded polymer was e xamined by using heat insulating layer-coated molds. Linear type polyi mide (PI) and ABS resins were used as the heat insulating material and molding polymer, respectively. Although the transferability of the mi rror-finished mold surface depends both on the thickness of PI layer a nd on the molding conditions, ag., temperature of polymer and temperat ure of mold, the PI layer of more than 0.2 mm thickness is necessary t o obtain sufficient transferability. In order to examine the relation between the thickness of heat insulating layer and the improvement of surface transferability due to the PI layer, the time-dependent temper ature distribution near the mold-polymer boundary was numerically stud ied. The results showed that the temperature of PI layer coated on the mold surface rises immediately after the layer is in contact with the polymer melt, and that the period during which the mold surface tempe rature is kept high increases with increasing the PI layer thickness. We therefore concluded that the blow pressure applied during the perio d is effective for improving the surface transferability of the molded article.