Thermosetting plastics (thermosets) refer to a range of polymer materials that cure, through the addition of energy, to a stronger form. The energy may be in the form of heat (generally above 200 degrees Celsius), through a chemical reaction (two part epoxy, for example), or irradiation. Thermoset materials are usually liquid or malleable prior to curing, and designed to be molded into their final form, or used as adhesive.
Thermoset polymerresins can be transformed into plastics or rubbers by cross-linking. Energy and catalysts are added that cause the molecular chains to link into a rigid, 3-D structure. A thermoset material cannot be melted and re-molded after it is cured.
Thermoset materials are generally stronger than thermoplastic materials. They are also better suited to high temperature applications. They are not easily recyclable like thermoplastics, which can be melted and re-molded.
As soon as the plastic cools to a solid state, the mold opens and the finished plastic is ejected from the press.
It differs from compression molding in that the plastic is heated to a point of plasticity before it reaches the mold and is forced into a closed mold by means of a hydraulically operated plunger.
As the plastic extrusion comes from the die, it is fed onto a conveyor belt where it is cooled, most frequently by blowers or by immersion in water.
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