How Molten Plastic Becomes A Shape

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PVC Plastic has become such a complete part of modern life that we take it for granted, but on further examination, the process followed by plastic manufacturers to get a quality, consistent result, is actually quite complicated.

Plastics extrusion is highly automated, and operates continuously without much in the way of human intervention. This has driven the cost of production down to the levels we see today, making plastic a very inexpensive material.

The process can best be described as forcing molten plastic under pressure through a die to produce a specific product. The range of products varies from short items cut to length such as piping or tubing, through to continuous plastic sheeting.

Plastic granules or resins are gravity-fed into a hopper connected to a screw drive with a dual purpose - to mix the plastic if more than one type is being used, and to melt the plastic as it makes its way through the screw drive.

Following is a list of some of the various different plastic extrusion examples, and a short description of how the manufacturing of each occurs:

Standard Plastic Extrusion:

The liquid plastic is screened through a filter to remove any particles, then forced through the die and into a cooling bath before being cut into lengths or rolled into sheets, depending on the product requirement.

Sheet/Film Extrusion:

With regard to plastic film or sheeting, the blend is pulled through a succession of cooling rollers. These rollers do two things; cooling the plastic and deciding the thickness and textures of the sheeting. The liquid packaging industry relies on plastic extrusion to meld plastic to paper and also aluminium foil to create such packaging staples as juice cartons and wine casks.

Blown Film Extrusion:

Blown film extrusion is used to make plastic shopping bags. When the product reaches the die, in this case an upright cylinder of varying dimensions, it is pulled upwards to a height ranging from a few metres up to 20 metres, depending on the amount of cooling it requires. Compressed air is forced into the centre of the extruded material, creating a bubble which is flattened by rollers into a double layer of film.

Tubing Extrusion:

The process is the same until the product reaches the die, which has a pin in the centre to create a hollow cross-section which becomes tubing. This pin is connected to a pressure source to stop the tubing from collapsing when it enters the cooling bath.

Plastic manufacturers use a range of materials in extrusion including polyethylene, polypropylene, acrylic, nylon, polystyrene and polycarbonate, among others. The versatility and cost effectives of PVC plastic makes it an essential product material which will continue to evolve as technological advances bring new processes on line.


Copyright (c) 2010 Nadine Davis

About the Author:
Plastic Manufacturers are able to use the process of creating PVC Plastic, using continuous production runs to create economies of scale. See Pacific Plastics for more info.



Article Originally Published On: http://www.articlesnatch.com


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