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Stretch film (or stretch wrap) is a plastic film typically manufactured from Linear Low Density Polyethylene (LLDPE), and is used for pallet wrapping, bundling and securing. This wrapping of a product or pallet of products with stretch wrap helps to protect the item from damage and loss.
Stretch film has two main methods of application:
Additionally, stretch film is made using two main manufacturing methods: blown and cast.
In this article, we'll explore:
Cast stretch wrap is manufactured using a cast extrusion process. A granular resin is fed into a heated screw barrel, which melts the resin. This melted resin is then fed through a flat narrow slot (also called a die). The sheet of material this creates is then passed over chilled rollers to quickly cool and solidify the film.
The dimensions of the die, as well as how fast the film is pulled away from it, determines the thickness and width of the stretch film.
This cast extrusion manufacturing process results in cast stretch film having a range of benefits:
Blown stretch wrap is manufactured using a blown extrusion process. Similar to cast stretch wrap, a granular resin (and any additives) is fed into a heated screw barrel, which melts the resin. This melted resin is then blown through a circular die, creating a bubble.
The volume of air blown into this tube stretches the tube/bubble out to the desired width, while the speed at which it is being blown through the die determines the thickness. This air also slowly cools the film, with this slow cooling process being one of the reasons for the film's hazy and dull appearance.
Nip rollers can then flatten this material into a tube that can be reeled for creating bags and pouches, or it can be slit and then reeled for creating a flat sheet of film.
This blown extrusion manufacturing process results in blown stretch film having a range of benefits:
Stretch film is one of the most versatile packaging products on the market, discover more about the benefits of stretch film.
These processes give cast and blown stretch wrap key differences.
Cast Stretch FilmBlown Stretch Film Cooling Fast Slow Appearance Very Clear & Glossy Hazy & Dull Puncture/Tear Resistance High Very High Stretch Resistance Moderate High Unwind Noise Low High Resin Molecule Alignment Linear Random Cling Consistent Cling High Level of Cling Durability Moderate Very HighNo matter which manufacturing method you opt for, Industrial Polythene can provide more environmentally friendly stretch wrap which contains at least 30% Post-Consumer Waste (PCW).
PCW is waste that is left over after it has served its original purpose as a consumer item. By recycling this plastic into new products, we reduce the amount of waste that is sent to landfill or incinerated; disposal methods that are very harmful to the planet and contribute heavily to climate change.
Find out more about our eco-friendly packaging solutions.
With their unique characteristics and properties giving them different advantages, which stretch wrap is better?
If looking at the industry statistics, one would think cast wrap the clear winner, with 70-80% of organisations opting for it.
However it's also important to consider the application. Cast stretch film is the best choice for some uses, while blown stretch film is the best choice for others.
For example, blown stretch wrap has higher durability and a high tear and puncture resistance. This makes it the better option for wrapping sharp-edged products and heavier loads.
On the other hand, cast stretch wrap is used more for light products and loads stacked on pallets. It's clarity makes it the ideal choice when you need to scan barcodes and see labels through the film.
Looking for stretch wrap for your organisation? Get in touch with Industrial Polythene to request a free sample or discuss your requirements and our friendly expert team will help find the perfect solution for you.
Stretch film is used in a variety of industries and it is important to choose the best one for each specific application. The two different types of stretch film are blown and cast, with the primary difference between the two being the process in which each is created and manufactured. These differences also impact the usability and price of the film.
Are you interested in learning more about China Stretch Wrap Dispenser? Contact us today to secure an expert consultation!
Creation of Cast Stretch Wrap
A cast extrusion process is used to manufacture cast stretch film. Beads of resin are fed into a heated barrel and forced through a narrow slotted die, creating a 'sheet' of film. The film is then fed along a rolling path that has been cooled, solidifying the film. This process is faster and costs less than the blown extrusion method as more is produced per man-hour. Machine stretch wrap is commonly produced by this method.
Creation of Blown Stretch Wrap
The blown film extrusion process to create blown stretch film is similar to the cast extrusion process. Beads of resin are fed through a heated machine with a circular die, then forced through the die and blown out vertically into a bubble. As this formed bubble finishes the process of being transformed into rolls of stretch film, it is cooled by the surrounding air. This type of film generally costs more to make because the output per hour is less than with cast films. Hand stretch wrap is often manufactured using this process and typically has higher holding power and puncture resistance.
Which Type of Stretch Wrap is Better?
Choosing the best stretch film is dependent on the wrapping situation. Load retention, film memory, film yield, puncture resistance, cling, visual clarity, and unwind noise are the main factors that need to be assessed before deciding which film is best suited for your situation.
7-Point Comparison Chart
Cast Stretch Film
Blown Stretch Film
Load RetentionStretches easily, which can cause shifting
More holding power, won't re-stretch once applied
Film MemoryMinimal shrinking back to the original state after stretching
Higher shrinking back to original size after stretching
Film YieldMore stretch to wrap more pallets with less film
Less stretch requires more film to wrap pallets
Puncture ResistanceStandard tearing can occur with high-stress
Greater resistance to breaking
Cling of the Film2-sided cling allows pallets to stick together
1-sided cling for higher load retention
Visual ClarityPerfectly clear, easy to scan and read, higher gloss creates reflections
Not crystal clear, difficult to scan and read, low gloss reduces reflections
Noise of UnwindVery quiet when releasing from the roll
Loud when releasing from the roll
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