RIM Process
With the Polyurethane Reaction Injection Molding Process – the Reaction Makes All the Difference!
Plastic injection molding has almost the same name, so even experienced engineers and designers might think they are the same. But “reaction” signals a big difference. Unlike plastic injection molding, the polyurethane reaction injection molding process, or RIM molding techniques, utilize low-viscosity liquid polymers in thermoset – not thermoplastic or thermoforming – processes. Through a variety of chemical reactions, these polymers expand, thicken, and harden only after they’re injected into the heated mold, accommodating much more intricate designs than ordinary plastic injection molding.
Raw materials and polyurethane reaction techniques can be selected and even customized to precisely deliver desired weight, strength, density, and hardness characteristics. The result is large polyurethane parts with a much lighter weight than those created by more commonplace processes.
A 360 View of RIM Products & Parts
RIM Molding Chemistries, Pressures, and Temperatures
Since these liquid polymers require less pressure (~100 psi) and lower temperatures (~90°) than typical ingredients, they can be injected into cost-efficient aluminum molds, lowering tooling costs. The molds are then moderately heated (~190°), but the resulting exothermic reaction quickly brings the materials to (~325°) and promptly cures the part inside the mold.
Structural Foam RIM (94V-0)
A closed-cell polyurethane two-part chemical system that uses a chemical blowing agent to create a cellular structure within the material. Provides unique properties, including high strength-to-weight ratios, thermal insulation, and sound deadening.
Shore Hardness: 66D – 81D
Tensile Strength: 3,100 – 4,800
Flex Modulus: 160,000 – 240,000
Min. Wall Thickness: .250”
Flexible Foam RIM
Integral skin foam forms a dense outer layer (or skin) during the foaming process. The skin provides a durable, non-porous, and aesthetically pleasing finish
Shore Hardness: 18 – 45A
Solid (“Rigid”) RIM (94V-0)
Rigid RIM produces high-quality, lightweight, and strong plastic parts with complex geometries with high strength-to-weight ratios, durability, and precision.
Shore Hardness: 75D
Tensile Strength: 7,000
Flex Modulus: 290,000
Min. Wall Thickness: .125”
Elastomeric RIM
Elastomeric systems produce plastic parts with excellent mechanical properties, including high elasticity, strength, flexibility, durability, and high impact resistance.
Shore Hardness: 65D – 71D
Tensile Strength: 3,700 – 7,000
Flex Modulus: 50,000 – 200,000
Min. Wall Thickness: .125”
DCPD
Though DCPD is NOT polyurethane, the material is processed using the same RIM process to produce parts that can replace materials from steel to composites. The system balances strength and toughness with excellent resistance to harsh chemicals and hot, wet environments.
Shore Hardness: 82D
Tensile Strength: 6,700
Flex Modulus: 274,000
Min. Wall Thickness: .250”
RIM Processing Equipment – Dispensing Machine and Hydraulic Press
The RIM molding process begins with polymer liquids (polyol and isocyanate) stored in large storage tanks and dispensed by large, high-pressure industrial pumps. The polymers are recirculated from the storage tanks to a multi-stream mix-head on the machined aluminum mold and back to the storage tanks in a continuous loop.
Advantages of a Polyurethane Reaction Injection Molding Process
From customers and end users alike, your products are going to get a better reaction. Watch our video to learn more!
Reaction Injection Molding (RIM) vs Other Processes
Comparison gives us a very positive reaction.
Reaction injection molding has many benefits: low tooling costs, short lead-times, large lightweight parts, high tolerances, enhanced design finish, desired chemical resistance properties, 94V-0 and HB ratings, customizing part properties, and molding over metal, wood, glass, computer chips and other parts.
Reaction injection molding is generally most cost-effective for the production of a few hundred to several thousand parts, but one RIM Manufacturing client has looked to us to produce more than 1,000,000 parts per year for 10 years.