A method for predicting the mold-filling and curing dynamics associated with heat generation caused by the chemical reaction of epoxy compounds has been developed. To verify this method, transient temperature profiles were measured during the mold-filling and curing process for two kinds of compounds used for encapsulation of semiconductor devices. After the completion of fill, temperature exceeded the mold temperature. The calculated temperature profiles for both compounds fit well with the experimental data. Calculated cure profiles showed that the cure was faster near the wall than at the center due to a quick temperature rise produced by heat conduction from the mold. On the other hand, within the usual filling time, the degree of cure remained very small. Calculated viscosity profiles were compared between this new model and the conventional model, which neglects heat generation, for two kinds of circular flow channels. Differences in the viscosity profiles were not found under several molding conditions due to the small curing advancement up until gelation.

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Phenolic resin is used in many automotive parts, electrical appliances, and other mechanical parts, because it is superior to many thermoplastics in heat resistance, electrical insulation and fire-resistance. Phenolic scraps, however, can not be remelted for recycling and voluminous wastes mest be dumped in landfill sites. The prime purpose of this study is to develop a material recycling technology to reuse the wastes in the molding process. The results obtained are as follows: (1) The generation of dust particles could be controlled by adding alcohol to the mxture of crushed waste material and virgin compounds. The result is that recycled compounds with virgin compounds could be conveyed to the molding process for reuse without generation of dust particles. (2) We checked the moldability in injection molding. In consuquence, it became evident that recycled compounds which have 33wt% of crushed materials possesses the same moldability in appearance as 100% virgin molding compounds. (3) We executed the mechanical properties, tensile test, frexural test and deflection temperature test. We reached a conclution that recycled compounds which have 23wt% of crushed materials possesses the same mechanical property as 100% virgin compounds. (4) This recycling technology can be put to practical use and should contribute to the reduction of environmental impact.

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The sandwich injection molding technique can be used in a wide range of engineering applications. In this study, the development of core materials and the break through phenomenon in sandwich injection molding were investigated. The samples were preferred using a bar-flow mold. The dependence on the viscosity and the injection speed of skin/core materials were studied. It was noted that the core material tends not to completely penetrate through the skin material the “break through” phenomenon. It is considered that the break through phenomenon depends on the melt strength of the freezing skin layer at the flow front.

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