Establishment of new molding system for long fiber reinforced thermosetting resin

The phenol resins have been used in a wide range of field because of low cost, good mechanical properties and good heat resistance. However, since the impact strength is lower than other resins, they are often used as fiber reinforced composites. A way of improving the impact strength and the mechanical properties is to leave long fibers in a product. There are several molding methods of forming products using long fibers, but their cycle times are relatively long. Therefore, they are not suitable for mass production. The purpose of this study is to establish a new molding system which can leave long fibers in a product and whose cycle time is short. The new molding system is based on transfer molding. Unlike general transfer molding, there is an injection unit for supplying a melted material into the transfer pot. Furthermore, in the injection unit, induction heating is used as a heating device and there is no nozzle at the tip of the cylinder. In the molding process, the cylinder in the injection unit is rapidly heated by induction heating and long-fiber pellets are melted by a screw within the cylinder. The resin tends to be curing because the temperature of the cylinder is high by induction heating, so there is no nozzle in order to prevent curing. The melted material is injected into the transfer pot in the mold and molded by pushing the material into a cavity with a plunger like general transfer molding. By using induction heating, the cylinder is heated and resin is melted rapidly. Thus, metering time is short and the fiber length is left long. Generally, a band heater is wrapped around the cylinder, so it takes time to cool the cylinder. On the other hand, the cylinder of the new molding system is uncovered the band heater, so the cylinder can be cooled quickly and it can immediately shift to the next cycle. Because of short time to heat and cool the cylinder, the new molding system can continuously mold a long-fiber product within 3 minutes.