Blown Film Extrusion

Blown Film Extrusion

The manufacture of plastic film for products such as biohazard and autoclave bags and continuous sheeting is achieved using a blown film line. Polymer melt from an extruder is fed through an upright die with an annular opening. There are several types of dies that can be used, depending on final requirements of film quality and characteristics of the polymer melt: spider, crosshead, and spiral dies.

Air pressure is introduced through the extrusion die so that after the polymer melt leaves the lip of the die, it expands in circumference. The tubing is also drawn along its length faster than it is being extruded. This leads to thinning of the film as it is expanded in both directions.

As the film is drawn upwards, it is cooled by a ring of air blowers. After solidification, the blown film tube continues to be cooled as it is pulled up by several sets of rollers, deflating the film to form lay-flat tubing. The flat film is then wound on a spool before further processing or shipping. At this point, the film is ready for further processing, such as printing or cutting into final shape.

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 Citations, attribution, and content source(s) for this article

Wikipedia contributors, "Die forming (plastics)," Wikipedia, The Free Encyclopedia, (accessed August 13, 2022).

 Used with permission under the terms of the Creative Commons Attribution-ShareAlike 3.0 Unported License (CC BY-SA 3.0)

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