When it comes to making a decision on the type of stretch wrap to use, the experts at AAA Polymer are here to help guide you to the best decision. In general, there are two different types of stretch wrap: blown stretch wrap and cast stretch wrap.
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There are significant differences in the two types of films ranging from the manufacturing process to the application use. Continue reading to learn more about the differences and benefits of each.
Cast stretch wrap is created through a cast extrusion process, which starts with a granular resin being fed into a heated screw barrel. Then, the molten resin is continuously fed through a narrow slot die. The thickness and width of the stretch wrap is actually determined by the dimension of the slot in the die.
After passing through the die, the resin is immediately fed over a chilled roller, which quickly solidifies and cools the film. Tension rollers are used to draw the wrap to the winding and slitting stations.
The cast extrusion manufacturing process results in cast stretch wrap having a unique set of benefits:
Blown stretch wrap is made through a blown film extrusion manufacturing process. It begins similarly with the granular resin as well as any additives being fed by a heated screw barrel. The resin is then forced into a circular die. Afterwards, the hot resin is vertically blown upward and outward, which is typically referred to as a bubble.
Instead of being cooled quickly, the bubble is cooled gradually by air as it goes up the tower. This slow cooling process is one of the reasons the wrap looks hazy and dull. Once it rises to the very top of the tower, the film is nipped together and drawn down to the winding and slitting stations with guide rollers.
The blown film extrusion process of manufacturing lends blown stretch wrap its own set of benefits, such as:
Many tests have concluded blown stretch wrap will stretch further than cast. However, blown stretch wrap requires more force. In some instances, you may be able to achieve a greater yield or better stretch with cast stretch wrap, but the additional stretch can be counteracted by using a lower micron blown stretch wrap.
The mechanical properties of blown stretch wrap allows users to possibly down-gauge to a thinner stretch wrap while maintaining load stability on your pallets. When you use a thinner stretch wrap, you can save money and reduce the amount of plastic waste for end users.
When Linear Low Density Polyethylene (LLDPE) is stretched, the molecules within the stretch wrap excite, which causes the stretch wrap to retract. In comparing blown and cast stretch wrap, blown stretch wrap has a much higher degree of memory.
The orientation of the molecular chains produces a stretch wrap that will contract in both cross direction (CD) and machine direction (MD). Cast stretch wrap, however, has a single orientation and "softer" characteristics, which causes it to have a reduced memory.
Cast stretch wrap is extremely clear and produces the highest levels of clarity. This clarity is directly related to how the wrap is manufactured. By casting the molten resin over a frozen roller, crystallization is reduced and clearer film is produced.
In contrast, blown film is cooled slowly, which increases crystallization and reduces the clarity. Because of this, many people choose the clarity of cast stretch wrap when using barcode scanners.
Blown stretch wrap has less gloss. This attribute reduces the amount of reflection under warehouse lighting, which allows easier product scanning and identification. Cast stretch wrap has higher levels of gloss, which is the result of the quicker cooling process as well as the types of resin used in the manufacturing. In the most warehouse operations, high gloss may not be as significant of an advantage because it may be difficult to scan or see through the film with standard warehouse lighting.
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Since , the experts at AAA Polymer have been helping business owners choose the best stretch wrap for their needs. Regardless of the type of materials you are looking to wrap, our experts will conduct a thorough needs analysis.
Afterwards, we will suggest the material that will save you the most money and that's best for your application.
Contact AAA Polymer today for your free money-saving stretch wrap consultation.
Stretch wrap is a plastic film that is used to keep products tightly bound during transportation. Warehouse operators use the film to wrap their products onto pallets, reducing damage to goods, discouraging tampering, and reducing injuries.
There are two primary types of stretch films: Cast stretch film and blown stretch film. They differ in both their manufacturing process as well as their applications, with warehouse operators needing a thorough understanding of the perks and drawbacks of both.
As the name suggests, cast stretch film is created through a cast extrusion process. This involves a molten polymer being extruded through a slot die, which determines the film's eventual thickness and width. From there the film is fed onto a cool roll to solidify it, before being made into large rolls.
The resultant film has a few advantages, including:
The blown film extrusion process creates stretch film by blowing heated resin vertically into a bubble, which is then left to cool by air instead of by a roller. As a result, blown stretch film has a far more hazy and dull appearance when compared to the clarity of cast stretch film. It does however have its own advantages, including:
The two manufacturing processes produce films that have different strengths, but also weaknesses.
Cast stretch film does not have the same high holding power that blown stretch film provides, making it better suited to lighter loads. It also tears more easily than the highly durable blown film and doesn't handle sharp edges as well. However, cast film is cheaper to manufacture than blown wrap, due to the more resource intensive manufacturing process, and it's well suited to irregularly shaped objects.
While more expensive to produce, blown wrap instead is far more suited to heavy loads with sharp edges. It's louder when unwound from rolls, and it has lower clarity caused by crystallization during manufacturing that makes it less favorable if product visibility is a factor. It also grabs onto itself during wrapping, which makes it less suitable to high-speed environments than cast wrap, which merely clings.
Ultimately, both types of film will be suitable to the majority of applications required. Choosing between the two types of film will depend on specific factors such as load weight, product shape, and durability. Warehouse operators should test their film performance and consider their application requirements when looking at which type of film to invest in.
At Stretchtape we offer blown and cast banding stretch film from 28 gauge to 500 gauge. Our machine-grade stretch film is manufactured using the cast extrusion process, as well.
Our film is used in various industries such as automotive, sports medicine, healthcare, construction, and apparel industries. Customers also benefit from highly customizable options, ensuring the film meets their needs.
Learn more about our stretch film products here, or speak to an expert at 216-486-.
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