RIM is a process where reactive liquid components-usually thermoset polyurethane-are mixed inside a closed mold cavity under pressure. This process is widely used in the automotive industry to produce internal and external parts.
Reinforced Reaction Injection Molding (R-RIM) is a close-molding process. Two resins are heated separately and poured into a mixing container with milled glass fiber. Once the resins and milled fiber are blended, the composite mixture is injected into a mold cavity and compressed. The resin quickly reacts and cures to form a composite such as a Class-A automotive body panel.
Structural Reaction Injection Molding (S-RIM) uses glass fiber fabrics, mats and preforms to make structurally strong composites. In SRIM, a thermosetting urethane resin is mixed at high pressure just prior to injection into a hot mold containing the fiber reinforcement. The composite mixture solidifies into a finished part such as large pickup truck boxes, and can be foamed to make low density nonstructural parts such as interior trim panels for cars.