How Stretch Film Is Made

Posted by Jerad Dowler on Thu, Mar 19, 2015

The highly interesting television show How It’s Made has created an interest in learning more about how everyday items are made. It has shown audiences that there is a lot that goes into making things that are easily taken for granted, and that is perhaps what makes the show so fascinating. However, one thing that the show hasn’t covered yet is stretch wrap.

Manufacturing_130Knowing a little bit more about this product can actually help you get the most out of your stretch film at work. Whether it means changing the type or the approach that you use to wrap your products, a little knowledge of stretch film can go a long way.

The first thing to know is that there are two ways to make stretch film. Both processes create a film with distinct advantages and disadvantages. There are also several traits that both types of film share, such as durability (meaning they do not tear as easily as other types of wraps). 

Cast Stretch WrapManufacturing_133-1

As the name of the film suggests, the process to produce it is called the cast extrusion process. The first step requires the melting of thermoplastic material so that it can be squeezed through a flat die. From the flat die, the melted thermoplastic goes onto a chill roll where the film becomes solid, similar to the cooling of plastic. 

This process makes it easier to see through the wrap, and when you unwind it from its roll, this film is much quieter than second type of film. If you do not want to use a machine as you package your goods, there are also hand grade casts films. 


Blown Stretch Wrap

The process to produce this wrap is blown extrusion. Like the cast extrusion process, the thermoplastic material is melted, but it is then squeezed through a slit die that is annular and has a hole located in the center. It stands vertically so that the process creates a thin walled tube that inflates like a balloon when air is forced through the hole. The tube’s top has an air ring that cools the melted material.

The process is more complex than the process used to make cast stretch wrap, which is why this wrap can be more expensive. Blown stretch wrap is more opaque because it tends to crystallize during the process. As a result you lose some of the visibility of your goods. It is also considerably louder as it is removed from the roll as it is securing your packages.


What Type of Film Does Paragon Manufacture? 

Here at Paragon Films, all of our films are manufactured by the cast extrusion process.  Many people ask, "What's better, Cast or Blown?"  Our opinion is that the cast process generally produces a stretch film with characteristics superior to that of a stretch film made by a blown process. Casting of film provides more uniform gauge, better cling, and greater percentages of stretch than blown film. Cast film is superior to blown film in tear strength in the machine or transverse direction, which aids in the prevention of tear propagation.


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Topics: stretch film production, Cast extrusion, How it's made, Blown film

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