Reaction injection molding

From Plastics Wiki, free encyclopedia

Reaction Injection Molding (RIM) Involves the injection of liquid polyurethane systems into a mold. The components then polymerize within the mold. Typically, this low temperature process typically takes less than a minute to complete, including time for mixing, curing, and demolding.

This technique is a form of liquid injection molding (LIM). When short fibers (1.6 mm), carbon or mineral fillers are incorporated into one of the liquids to increase modulus and reduce coefficient of expansion the process is referred to as reinforced reaction injection molding (RRIM). RIM resin systems include epoxy which mold over continuous strand mat and preforms as well as polyurethane/polyester hybrids, polyurea and poly(DCPD).

Contents 1 Raw Materials 2 Tooling 3 Cost 4 Advantages 5 Disadvantages 6 Applications

Raw Materials

Liquid urethane in various combinations with liquid catalyst

Tooling

Machined aluminum, cast aluminum for higher volumes and complex part geometries, reinforced non-metallic tooling for lower volumes and prototypes.

Cost

Part cost is typically higher than injection molding. Tooling cost is a fraction of injection molding tools.

Advantages

Large format parts with complex, 3-dimensional geometries possilbe. Varying wall thickness without warpage or sink marks possible with polyurethane structural foam.

Disadvantages

Slow cycles, expensive raw materials.

Applications

Automotive spoilers, interior trim panels for automobiles and trucks. Structural parts and enclosures for medical devices, electronic and industrial application.