抄録
In the injection molding of glass fiber reinforced thermosetting plastics as BMC (bulk molding compound), the cavity pressure, which influences the molding state and the mechanical properties of parts, seems to behave very complicatedly, because the curing reaction is completed in the mold cavity. In order to clarify this behavior, nozzle injection pressure, cavity pressure, and injection plunger displacement have been measured. Moreover, with the thermocouple inserted in a molded part, the temperature change was measured during curing of BMC. The main results obtained are as follows: 1) The injection speed of BMC into the mold cavity increased with the rise of the mold temperature. Both the air in the cavity and the flow of flash influenced the behavior of the cavity pressure. 2) The maximum cavity pressure after charging was much higher than the injection set pressure because of the thermal expansion of the resin, and this maximum pressure differed greatly with the location in the cavity. 3) In process of curing, the shrinkage of the resin was more than its thermal expansion, therefore the cavity pressure soon became to zero. 4) The curing time of BMC became shorter with increase of the mold temperature.
