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The process flow of a plastic sheet extruder during production.

Time：

2018-08-25

Extrusion molding is a manufacturing process in which materials are heated and pressurized within an extruder, causing them to flow continuously through a shaped die to produce plastic products. Extrusion accounts for a significant share of plastic processing; globally, more than 60 percent of plastic products are manufactured using this technique. All thermoplastic polymers can be processed by extrusion, and in recent years, with advances in extrusion equipment, extrusion has also been applied to the processing of certain thermosetting plastics. A defining feature of extrusion molding is that the resulting products have cross‑sections consisting of continuous lengths of material, such as pipes, profiles, sheets, films, monofilaments, wires, cables, and extruded plastics.

Extrusion molding is a plastic‑processing method in which material, heated and pressurized within an extruder, flows continuously through a shaped die to form a finished product. Extrusion accounts for a substantial share of plastic processing; worldwide, more than 60 percent of plastic products are manufactured via extrusion. All thermoplastic polymers can be processed by extrusion, and in recent years, with advances in extrusion equipment, the process has also been applied to certain thermosetting plastics. A defining feature of extrusion molding is that the resulting products have cross‑sections consisting of continuous lengths of material, such as pipes, profiles, sheets, films, monofilaments, wires and cables, and extruded parisons.

Cast film extrusion is a method for producing thin films. In the manufacturing process, a liquid resin or dispersion is first coated onto a substrate—typically a metal belt—and then cured by an appropriate technique, after which the film can be peeled off the substrate. By combining extrusion with cast film technology, high‑performance thermoplastic sheets suitable for thermoforming can be produced.

The plastic sheet extruder heats the material, blends pellets, powders, crushed scrap, or regrind, and removes entrapped air before extruding it through a die. Depending on the type of plastic and the desired thickness, the hot extrudate is either drawn and shaped or conveyed onto synchronously rotating take‑up rollers equipped with cooling (roller‑cooling process). The extrudate then passes through a cooling section, after which it is edge‑trimmed and wound into rolls. The sheets are cut to specified dimensions. Both single‑layer and multilayer molded materials can be produced.

The extrusion‑calendering process enables the production of single‑layer and multilayer plastic thermoforming sheets, as well as multilayer co‑extruded laminates incorporating barrier materials such as EVOH and PA, using resins including PP, PS, CPS, and HIP5.

Cast‑film thermoformed sheets are primarily used to manufacture thin, vacuum‑formed thermoformed products. They can also be processed on positive‑pressure thermoforming machines to produce plastic cup lids and large‑stretch square or round cups, and on thermoforming machines that combine positive and negative pressure to fabricate food trays and fresh‑produce containers in a variety of specifications. For example, cast‑PP thermoformed sheets are suitable for making jelly cups, pudding cups, disposable cups, plates, bowls, lids, and inner packaging for frozen foods. Cast‑PS thermoformed sheets are ideal for packaging stationery, industrial components, and toy casings. Containers made from cast‑film thermoformed sheets with a PP/EVA/EVOH/PP multilayer structure offer excellent barrier properties against oxygen, carbon dioxide, and water vapor, thereby extending product shelf life; they are well suited for packaging canned goods, jellies, and puddings.