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Your partner in precision urethane-based technology from prototype to production.

MPC Polyurethane Knowledge Center

Materials for Reaction Injection Molding (RIM)

Reaction Injection Molding (RIM) is a manufacturing process typically used to manufacture large, complex geometries. Unlike injection molding, RIM uses thermoset materials and never thermoplastics. For this reason, polyurethane solids and foams are most commonly associated with RIM. In this post, we will further uncover the five types of RIM materials available for your product design.

Elastomeric Polyurethanes

Elastomeric PolyurethanesElastomeric polyurethanes are formed through the reaction of isocyanates and polyols, making this material a true polymer. Similar to cast materials, elastomeric RIM polyurethanes can be made in a hardness range between 25A to 75D. Besides being extremely flexible, elastomeric polyurethanes can exhibit excellent corrosion, abrasion, wear, and impact resistance. For this reason, elastomeric RIM products are often found in various medical, automotive, industrial, and military & defense applications to name a few. Depending on your design requirements, elastomeric materials can either be pigmented or painted. Painting, however, does require additional steps and specific paints to prevent cracking when in use.

Structural Foams

Structural Polyurethane RIM FoamStructural polyurethane foams are typically formed through a unique foaming process and feature a key set of materials. These highly moldable materials are often classified to be extremely durable, stiff, and lightweight. In fact, structural foams often replace injection molded plastics due to their superior properties. Because of this, structural foams are commonly found in applications that require high-end, rigid housings and cabinetries. For example, structural foams surround and protect many electronic and medical devices. They can produce thicker cross-sections and feature a variety of surface finishes to mimic other common materials. For additional benefits RIM can offer your product design, click here.

Rigid Foams

Rigid Polyurethane RIM FoamDespite the name, rigid polyurethane foams are not comparable to structural foams. Instead, this material generally resembles a similar look and feel to molded Styrofoam plastics. While both materials are structured and stiff, rigid polyurethane foams offer a different set of physical properties. For instance, this material can achieve both low and high densities and resist most chemicals, tear, and shock absorption. Because of this, rigid foams are typically favored for applications such as flotation devices, filling voids, or protecting assemblies.

Flexible Foams

Flexible Polyurethane RIM FoamFlexible polyurethane foams include a wide variety of elastomeric foams that can achieve high densities while remaining flexible. Some materials provide the option to have a skin-like surface finish or exposed microcellular foam texture. As an example, integral skin foams can usually be identified by their smooth, shiny appearance. Typically, this feature is favored for products that require easier cleaning and longer wear life. Flexible polyurethane foams can commonly be found in baby products, fitness applications, and medical devices to name a few.


Dicyclopentadiene (DCPD) Materials Dicyclopentadiene (DCPD) is not a polyurethane, however, this material can be processed using the RIM process. DCPD is a material generally made up of heated gas oils. While there are many types of DCPD materials, they tend to exhibit superior impact resistance. For this reason, DCPD can be seen in applications that typically require protective shields such as heavy machinery, automotive, and military & defense.



Which RIM Material Do you Choose?

Depending on your design requirements, there is a RIM material that can help bring your design idea to life! Unlike injection molded plastics, RIM materials offer superior properties and design freedom to produce large, complex geometries. When selecting the right material, it is important to determine your application's function, environment type, and key physical properties for better performance. At MPC, we specialize in custom formulations and manufacture a wide range of products and components through our proprietary cast and reaction injection molding (RIM) processes. If you are seeking material assistance for your RIM product design, take our design tool, here, or download our material data sheet below to learn more. 

Download Our Durethane Material Data Sheet

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