Reaction injection molding (RIM) involves two liquid components, an isocyanate and a polyol, which, when combined, undergo a chemical transformation. A composites technician mixes the two liquids and pours the resultant compound into the mold cavity. Inside the mold, the mixture catalyzes, generating exothermic heat as it solidifies into a stable, lightweight and homogenous final composite product. During the setting process, this exothermic release can result in temperatures up to 300° F inside the mold, yet pressures remain relatively low, typically no more than 50 psi.