Rim Plastic Reaction Injection Molding: How RIM Works

Rim Plastic Reaction Injection Molding: How RIM Works

Aside from properties like low weight and high strength, RIM plastic Reaction Injection Molding parts have other features like thermal insulation, heat resistance, dimensional stability, and a growing rate of dynamic properties. They also have the capability to restrict inorganic and organic acids coupled with other toxic items and chemicals and other numerous solvents.

Another exciting feature about this tool is the ability to resist weathering and aging, though extreme exposure to sunlight leads to the change of the color at the surface.  The reason why the Reaction Injection Molding (RIM) process is more cost-effective than the other techniques for large parts is due to the low injection pressures ranging from 30 to 100 psi and low processing temperatures ranging from 95F to 150F and.

In general, it uses lesser energy to create the same injection molded thermoplastics and requires lesser floor space and equipment. There is no need to re-melt the solid thermoplastic thereby consuming less energy and there is a great reduction in the cycle periods of the Reaction Injection Molding.

How RIM Works

Two liquid materials – polyisocyanate component and resin mixture – are stored in the different unit of temperature-regulated feed tanks incorporated with agitators. Some reactions take place in these tanks: the polyol and isocyanate are passed across the supply routes to metering units that help increase the pressure of the reactants and pass it to the mixhead. At the start of the injection process coupled with the opening of the valves in the mixhead, the liquid reactants flow into a compartment in the mixhead at varying pressures (1,500 – 3,000 psi) where they are thoroughly mixed by an impingement of high speed. From the mix compartment, the liquid enters into the mold at an approximate atmospheric pressure characterized by an exothermic chemical reaction, which develops into the polyurethane polymer inside the mold. Both the short and cycle periods depend on the part size and the polyurethane system utilize. A normal mold for an elastomeric component may be filled within a moment and quickly undergo the demolding process in less than a minute.


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