Plastics, thermoset, open-mold process

In-mold decoration can be done with either injection molding of thermoplastics or compression molding of thermosets. Thermosetting plastics are decorated with a two-stage process. For melamine products, for example, the mold is loaded with the molding powder in the usual manner and closed. It is opened after a partial cure, and the decorative "foil or overlay is placed in position. 

Figure T.8 Transfer molding process (a) the mold is closed and material is placed in the pot, (b) the plunger descends into the pot, causing material to melt and flow through runners into cavities, (c) after cure, the press opens, the plunger retracts and the parts are ejected with cull and runners. (Ref Hull, J.L., Processing of Thermosets , Modern Plastics Handbook, CA. Harper, ed., McGraw-Hill, New York, 2000)...

For prototyping or for limited production runs, liquid plastics casting offers simplicity of process, relatively low investment in equipment, and fast results. T e casting materials may be thermoplastics, such as acrylics, or thermosetting plastics, such as epoxy resins. The plastics may harden by simple cooling, by evaporation of solvents, or by a polymerization or cross-liiiking reaction. Such plastics are often poured into open molds or cavities. Because pouring is done at atmospheric pressure, molds are simple, often made of soft metals, plaster, or other plastics. 

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