Abstract
We developed a new FRP flask with an injection molding system for microwave polymerization. This study evaluated the effects of additives to α-calcium sulphate hemihydrate combined with microwave powers on the temperature of the gypsum mold in the FRP flask during the polymerization process. The results were summarized as follows. 1. The use of the fiber optic thermometer allowed continuous temperature measurement of the gypsum mold in the flask during microwave irradiation, which exerted strong electromagnetic fields. This measurement was useful in accurately identifying the temperature distribution in the gypsum mold, which was affected by the rapid temperature rise and thermal conductivity during microwave polymerization. 2. The temperature of the gypsum mold was increased by electroconductive additives. The amount of the temperature increase was proportional to the quantity of additives. 3. Using 90W power for the microwave oven evenly decreased the magnitude of a rapid exotherm in gypsum mold, compared with that at 500 W power, leading to a more uniform temperature distribution inside the FRP flask.
