Reaction Injection Molding Process

Reaction Injection Molding

Two reactive materials are injected into a closed mold. They polymerize and set to final shape within the mold.

Capabilities / Processes / Reaction Injection Molding
Reaction Injection Molding Volume Graph

Raw Material

Two-part thermoset polymers commonly used for the RIM process include dicyclopentadiene (DCPD) and polyurethane. Reinforcing materials can be added as well, but are not necessary to make high strength, impact resistant parts.


Two-piece aluminum molds are typically used for the RIM process. Nickel shell constructions can be used to reduce tooling cost.


With appropriate tooling, Class A finishes are achievable on most RIM parts. With proper preparation, the materials accept paint very well and can be fabricated in the same manner as other composite materials.

  • High Volume Programs
    Short (4-6 minute) cycle times and the use of machined aluminum tooling support annual program volumes to >10,000 units.
  • High Impact Resistance
    RIM materials, notably DCPD, display very high impact strength and are ideal for applications that may encounter physical strikes from foreign objects.
  • Class A Surfaces
    The use of precision matched-die tools and the capability of the material produce Class A surfaces that can support topcoat finishes.
  • Mold in A- and B-Side Geometry
    The low viscosity of the reaction components and the use of tool action in the mold allows for many part features to be molded into the part, reducing or eliminating the need for secondary machining operations.

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