The 29th annual meeting of the Association of Rotational Molders had an interesting presentation on Rotomolding of nylon 6 parts directly from caprolactam monomer. Centro Inc. a well-known roto moulder presented a process that polymerizes liquid caprolactam in the mold. Called Rotomoulded Anionic Polymerization, or RAP, the process is claimed to offer cost savings relative to using standard nylon 6 resin. Centro developed the process with several other European companies. RAP has been used in Europe for several years to make fuel tanks, but Centro worked with several US and European companies (which it declined to name) to improve the safety and productivity of the process.

In the RAP process, a robot dispenses liquid caprolactam along with a catalyst as well as an activator into a heated aluminum mold, which is then rotated while the mixture reacts to produce a virgin nylon 6 part. The process is said to be faster than molding with nylon 6 and reportedly makes superior parts free of surface porosity. In addition, RAP makes it easy to customize formulations with pigments, impact modifiers and UV stabilizers, plasticizers, etc.
Centro is not currently offering to license it, but only to use RAP to make parts in house.