Liquid impingement molding

LIM Liquid impingement molding (now reactive injection molding, RIM)... 

LED light-emitting diode LEP Light-Emitting Polymer LIM liquid impingement molding LIM liquid injection molding liq liquid... 

The RIM process involves the high-pressure impingement mixing of two or more reactive liquid components and injection of the mixture into a closed mold at low pressures. Large and thick products can be molded using fast cycles with relatively low-cost materials. Its low energy requirements with relatively low investment costs make RIM attractive (9). 

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. 

This high-pressure impingement mixing delivery of two or more liquid urethane components to a very small mixing chamber that continuously mixes and injects into a closed mold delivers at rates approaching 650 lb/min. The liquid components are heated to maintain low viscosities. 

The basic principle of RIM is simple Two liquid reactants or prepolymers are mixed rapidly by high-speed impingement The mixture then passes into a closed mold where a major part of the polymerization process occurs to produce a finished solid part in a single step ... 

High conversions and molecular weights are obtained because reversible reactions and side-product removal is not an issue. In RIM processes, liquid monomers are mixed using impinging jets and must quickly flow into the mold before the reacting mixture becomes too viscous. The complete cycle time for injection, reaction and umnolding (so that the mold can be used to make the next product) is often only 30-60 s. RIM is used to produce rigid molded polyurethane automobile parts and polyurethane foam seat cushions [3j. 

A semicOTitinuous manufacturing process in which two liquid compmients are metered in the calculated ratio by high pressure piston pumps, mixed by impingement mixing and injected into a mold cavity or cavities, where the reactants are polymerized or cured. The process has been used to polymerize polyamides, elastomeric polyurethanes, and polyurethane foams. 

Reaction injection molding creates its own resin by mixing two highly reactive liquid components which react with each other by high-pressure impingement. The reaction is completed shortly after the resin is injected into the mold. This is accomplished at a pressure of 100 Ib/in, which permits the use of electro-formed and vapor-formed nickel lined epoxy, aluminum, and kirksite tools at a considerably reduced tooling cost. (Machined and plated cast steel molds can also be used.) As a closed-mold process, both sides of the part are finished and can have textures, raised numbers, and raised letters, but molded-in labels are not feasible. The finished part can be trimmed in the mold. 

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