In the 1960s, a chemist invented the use of polyurethane materials in Reaction Injection Molding (R.I.M.).
The chemist injected two liquid components of a polyurethane system. The components
mixed and flowed into the mold as a low-viscosity liquid. When the mold was
opened, the liquids had formed a polyurethane structural-foam material with a
foam core and a hard, solid outer skin.
The R.I.M. process includes two liquid components -- a
polymer resin blend and a modified disocynate --which are introduced to each
other via a high pressure mixing system, then injected into a closed mold at
low pressure. The reaction yields a polymer that takes on the details of
the mold cavity with high degrees of accuracy and repeatability. R.I.M.
materials have properties high enough to allow for the use in a combination of
structural and aesthetic construction, excellent weatherability and variable
wall-thickness.
Generally, R.I.M. molds cost less than those used in similar processes. This is because R.I.M. works with lower-cost mold materials, such as aluminum, nickel, and epoxy.