12 - Reaction Injection Molding

Abstract

This chapter discusses the concept of reaction injection molding (RIM). RIM is a relatively new manufacturing technology to produce high-quality principally polyurethane thermoset plastic or thermoplastic parts. Despite being relatively new, this technology has become a premier plastic-molding process that offers versatility in processing options and chemical systems that are used to produce high-quality and highly styled plastic products. The chapter provides a schematic of the typical RIM process. In RIM, two or more liquid intermediates are metered separately to a mixing head, where they are combined by high-pressure impingement mixing and subsequently flow into a mold where they polymerize to form a molded part. Advantages that are inherent in the process fall into three general categories: low pressure, low temperature, and use of reactive liquid intermediate. RIM is also called reactive injection molding. If a plastic system of the RIM type is sprayed against the surface of an open mold, the process is called expression reactive spray molding (RSM).