Mold design, RRIM

In the reinforced RIM (RRIM) process a dry reinforcement preform is placed in a closed mold. Next a reactive plastic system is mixed under high pressure in a specially designed mixing head. Upon mixing, the reacting liquid flows at low pressure through a runner system to fill the mold cavity, impregnating the reinforcement in the process. Once the mold cavity is filled, the plastic quickly completes its reaction. The complete cycle time required to produce a molded thick product can be as little as one minute. 

The formulations given below (in parts by weight) are three examples of typical formulations from the many available, which have been designed to meet specific requirements. Noteworthy points reading the formulations are explained. An example of formulation for reaction injection molding (RIM) and reinforced reaction injection molding (RRIM) is also given,... 

Recent advances in poly (urethane) reinforced reaction injection molded (RRIM) parts has led to use in components such as fenders for small trucks, low-density interior door panels, and higher heat-resistant body panels. Rear fenders on the Chevrolet Silverado and the GMC Sierra trucks (Fig. 2), made of RRIM polyurea, are the first application of a RRIM polymer designed to withstand electrocoat, primer, and topcoat paint line process temperatures. 

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