Plastic processes reaction injection molding

Important are behaviors associated and interrelated with plastic materials (thermoplastics, thermosets, elastomers, reinforced plastics, etc.) and fabricating processes (extrusion, injection molding, blow molding, forming, foaming, reaction injection molding, etc.). They are presented so that the technical or non-technical reader can readily understand the interrelationships. 

The late 1950s saw the emergence of cast elastomers, which led to the development of reaction injection molding (RIM) at Bayer AG in Leverkusen, Germany, in 1964 (see Plastics processing). Also, thermoplastic polyurethane elastomers (TPUs) and Spandex fibers (see Fibers, elastomeric) were introduced during this time. In addition, urethane-based synthetic leather (see LEATHER-LIKE MATERIALS) was introduced by Du Pont under the trade name Corfam in 1963. 

Reaction injection molding (RIM) is a fast, low-pressure, low-temperature, low-cost process for one-step conversion of reactive liquids into large finished solid plastic products. Liquid polyol and liquid diisocyanate are mixed by impingement, pumped instantly to fill a large mold cavity, and polymerize/ cure rapidly to form a thermoset polyurethane product. The cured polymer may be a stiffly flexible product such as automotive bumper covers, front ends, and trim or a rigid foamed product such as furniture and housings (cabinets) for computers, business machines, TY and radio. 

A specific attention has been paid to the mechanochemical generation of X in unsaturated elastomers, EPDM, ABS, PVC and polyolefins [243, 252]. This synthetical approach exploits processing operations producing free radicals. In situ chemical reactions can be performed during some important industrial processes like mastication of rubber and extrusion, mixing or reaction injection molding of plastics. 

Extensive use of flexible polyurethane fascia on automobiles has established RIM (Reaction Injection Molding) as a viable plastic molding process. 

For our purposes, reaction injection molding is defined as a process in which two or more reactive streams are combined and mixed with an impingement mixing device and injected into a closed mold where they polymerize to rapidly form a plastic part. To compensate for polymerization shrinkage, RIM parts are foamed to some degree. 

Special Processes. Several more recent developments have opened the possibility of special foam processes that may grow to tremendous importance and perhaps even change the entire concept of foamed plastics. These are structural foam, reaction injection molding (RIM), and syntactic foam. 

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