What is RIM?

Reaction Injection Moulding (RIM) is a low-pressure process for producing molded plastic parts. Polyol and isocyanate, along with optional additives, are first mixed and then injected as a reactive mass at 4–6 bar into a mould made of aluminium, polymer concrete, or ureol. The crosslinking reaction hardens the material inside the mould. RIM technology allows the production of both soft and hard polyurethane components, with various Shore hardness levels, including integral foam or elastomeric parts.

Compared to conventional injection processes, RIM features lower viscosity, which enables longer flow paths within the same wall thickness — making it ideal for thin-walled, large, and complex parts.

In small-batch production, moulds are mainly made from polymer concrete (PB).

Due to the high surface durability of such moulds, larger quantities can be produced using low-pressure RIM. In many cases, RIM is a suitable alternative to conventional spray moulding processes.