[1] A subset of RIM is structural reaction injection molding (SRIM), which uses fiber meshes for the reinforcing agent.
[1] The most common RIM processable material is polyurethane (known generally as PU-RIM),[2] but others include polyureas, polyisocyanurates, polyesters, polyphenols, polyepoxides, and nylon 6.
[citation needed] It also has the advantage of quick cycle times compared to typical vacuum cast materials.
[citation needed] The bi-component mixture injected into the mold has a much lower viscosity than molten thermoplastic polymers, therefore large, light-weight, and thin-walled items can be successfully RIM processed.
This thinner mixture also requires less clamping forces, which leads to smaller equipment and ultimately lower capital expenditures.