HIGH PRESSURE RESIN TRANSFER MOLDING
Resin transfer molding combines injection molding and the use of a reinforcement fiber material (composite component). High Pressure Resin Transfer Molding (HPRTM) is the next generation to the LPRTM process. With the use of a higher injection pressure in the mixing head and mold, faster cycles times can be realized. The process begins with the composite component being placed in the mold. Next, the resin is injected into a partially open mold. Once injection is complete, the mold is closed which forces equal distribution of the resin across the face of mold and reinforcement material. The mold venting located away from the injection points allows for air to escape. The vents can also be used to draw a vacuum can which can improve laminate quality.
As a variation of the RTM process, HPRTM uses higher injection pressures for the reactive thermoset mixture. The reactive mixture (e.g. polyurethane) is mixed and injected within seconds into the mold at pressures of up to 200bar. Due to the high pressure and the use of extremely reactive resin systems, cycle times are dramatically faster than in conventional resin transfer systems. The injection and subsequent impregnation of the fiber layup (glass, carbon fiber weaves or textiles) inside the mold typically utilizes vertical clamp style machines. The elevated injection pressures of HPRTM can require machines with clamping forces similar to conventional thermoplastic injection molding.