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Plastic Extrusion - A Look at the Process and Its Results
By Richard C. Milton

Plastic extrusion is responsible in the production of pipes or tubing, adhesive tapes, wire insulation and even window frames. It is a voluminous process where raw plastic is melted to form the desired product. The process starts with the use of a resin of thermoplastic injected or fed into the extruder's barrel. After this, colorants as well as liquid or pellet ultraviolet inhibitors are mixed with the resin.

In order to come up with the desired results of the process, a screw is used. The screw designs differ depending on the type of polymer used in the process. The screw designs in the thermoplastic screw have five zones namely the feed, melt, pressurizing, decompression and mixing zones. Aside from knowing this component in the process, it pays to look into the other parts of the procedure.

The plastic extrusion process

It is in the feed throat where the plastic material enters. Through that process, the plastic becomes closer to the screw. The screw's role is to make the resin move into the barrel. The barrel is heated depending on the temperature required by the molten plastic. Gradual heating is needed in order for the resin to melt consistently as they are pushed further to the other end of the barrel. Overheating may damage the quality of the material used.

The molten plastic ideally leaves the screw and proceeds through the so-called screen pack. It is in this particular part that contaminants are removed from the molten plastic. In order to make sure that the melting and mixing process is done uniformly, a breaker plate assembly is a valuable material to consider. From the breaker, the molten plastic goes to the die in order to form the product desired out of the material.

Products resulting from the plastic extrusion process

Once the design have been created in the die, there are greater possibilities of getting hold of the desired product. The most common examples are plastic sheets or film. This product requires thermoforming to soften the plastic and to produce a new shape. The film or plastic sheets from the process become important in food packaging industries.

Other products coming out of the plastic extrusion process are shopping bags out of a blown film. With the use of the process known as tubing extrusion, drinking straws and medical tubing are produced. Another subcategory in the process, known as extrusion coating, is responsible in tetrapak production.

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