Stretch film comes in varying gauges, lengths, chemical make-ups, colors and can be used in numerous applications. Not all stretch film works on all loads and for all applications. One interesting variable and starting point for stretch films is deciding between blown or cast manufacturing processes. But first, if you are unsure of the differences between shrink and stretch start with this blog post.
Blown stretch film is created by blowing heated resin out vertically into a bubble. The bubble is then transformed into rolls while it is cooled by the surrounding air. This simple animation shows the basics of the process. Alternatively, another way stretch film is manufactured is by feeding a sheet of heated resin along a rolling path with chilled rollers while the cooling solidifies the film. This process produces cast stretch film and like blown film is then turned into large master rolls. Check out this video showing the process.
Blown film is tougher and has less of a chance to puncture than cast. This occurs due to the slower cooling process, which allows the molecules in blown film to spread out as opposed to aligning in long lines like in cast. Blown film also has a higher level of cling (think Reynolds Wrap) than cast, making it stick to itself easier.
So, why would anyone use cast film? Cast stretch wrap has a clear, glossy finish allowing greater success with RFID and other scanning technology while blown film can be hazy and dull. Cast stretch film unwinds much quieter than blown. It is also easier to stretch and control the gauge with cast film.
Both films have great benefits for different applications.
What type of machine is being used, if not applied by hand?
What kind of load is being wrapped?
Where does your skid go after leaving your dock? Is it temperature controlled?
How is this skid transported and stored?
How many variants of loads does your facility wrap?
Do you use labels/barcodes under the film that need to be scanned?
Does your distributor ask you these types of questions and provide solutions based off of your answers?
If you are purchasing films based on the one with the cheapest price per roll, you may be surprised what kind of information and insight can be gained and the real savings you are missing out on. Our industrial packaging company represents several leaders in the market including Berry Plastics, Paragon Films, StretchTape, and Alliance Plastics with stock ranging from blown and cast hand and machine films, pre-stretch films, vented films, UVI, and specialty color films.
Orion Packaging has a deep line of stretch wrappers. With the (still pending) 2020 PackExpo in Chicago coming up quickly it had us thinking about some of our finds and top packaging suppliers in 2018. Orion debuted their newest Sentry iteration during the expo and it remains one of the best entry-level wrappers on the market for its low price, reliability, and onboard pre-stretch capabilities.
Check out some of the key features for the LP and HP versions:
200% powered prestretch film carriage: Helps you save on film costs and give you a superior holding force compared to hand wrapping or mechanical tension wrappers.
IntelleVue HMI: Full color,high resolution 7” touchscreen display with powerful microprocessor to stores recipes, user-manual and more!
3 Year warranty: Backs time tested designs and built to give you year after year of dependable, trouble-free operation with steel construction, heavy-duty components and reliable electronics.
4,000 pound weight capacity: On maintenance-free turntable with 52” x 52” x 80” load capacity.
12 Revolutions per minute: Delivers steady wrapping performance.
RevoLogic technology: Precisely applies the correct number of top and bottom wraps compared to competitive models.
One of the biggest “verbiage” misuses we see as an industrial packaging company has to be shrink film vs stretch film and everything in between like plastic wrap, cling wrap, or the like. If you get these terms confused also you are not alone. Let’s unpack it!
It’s true that both shrink and stretch films are designed to unitize products onto pallets and both are generally made from polyethylene resins. Another truth, shrink films are produced on blown film lines and stretch films can be produced on either blown or cast film lines. Outside of those similarities, the two packaging systems don’t have a lot of other common characteristics.
1. Material Make-Up
Shrink films contain a high percentage of low density polyethylene (LDPE), which is the same type of resin used to make bread bags and newspaper overwrap sleeves. When fabricated under very specific parameters, LDPE gives shrink film its “shrink” properties. The stress or tension required to make the film contract is frozen in during the fabrication process.
In contrast, most stretch films contain high levels of linear low density polyethylene (LLDPE) and, depending on the end-use application, can stretch from 25 to 300%.
Bottom line: Both films are made out of different forms of plastic, but the characteristics of that plastic make them very different items. Once stretch film is stretched, it relaxes back to give your palletized load a very tight “plastic” wrap effect whereas shrink film doesn’t do any good until you put some heat to it to “shrink” it to the product.
2. How it is Applied
To activate shrink film, a heat source is required such as a heat tunnel, heat gun, or torch. When sufficient heat is applied to the film, it approaches its melting point and the film begins to draw up or “shrink”.
Because the film can only shrink so far, each product to be wrapped has to be matched with a specific film thickness, size, and configuration of film – that is where product application testing comes into play.
Shrink film is applied like a bag or blanket over the object then either passes through a heat tunnel or an operator uses a heat gun to shrink the film to the product. In this example these bottles would have gone through a tunnel system.
Stretch films are either designed to be applied by hand or by machine. Hand films usually have minimal stretch (25-100%) in order to aid the operator in applying the product and are in many ways similar to a large roll of very thin tape or what households might refer to as cling wrap. Machine films on the other hand can have very high stretch levels (150 -350%) and they are applied by automated stretch wrapping equipment.
When stretch film is applied to a skid of material, the operator or machine will help stretch the film before wrapping – the film then relaxes back on itself, creating a strong load containment.
Bottom Line: Only stretch film can be applied by hand and shrink film – in any instance – must use some form of heat to activate its packaging properties.
Learn about the case sealer selector tool as another alternative.
3. Load Containment
As shrink film resins go, LDPE does not always have good puncture or tear resistance and has a relatively low load holding force for very heavy palletized loads. In order to provide sufficient load containment and protection for the load, these films are generally several times thicker than most stretch films at face-value. But, that doesn’t mean shrink options should be overlooked quite yet.
Machine stretch films can be configured to exert very high levels of tension on a load if desired, increasing load containment and puncture resistance on otherwise very difficult loads to wrap.
Think of it this way, a company might shrink wrap a pack of soda bottles together, but then once those packs are stacked onto a skid about 10 packs high they might stretch wrap them altogether to secure the load during transit.
Bottom Line: Stretch wrap is usually employed to hold loads and products together on a pallet for transportation or storage purposes. Shrink wrap generally protects single products from dust or weather or can help bundle products together like commonly seen with bottles of water or packs of vegetables. Both films have great value for the right application because they do very different things.
4. Common Applications
Shrink films are good for applications where the object requires five or six-sided protection (top and/or bottom and four sides) or is very large. As mentioned very common items that are shrink wrapped include vegetables, bottled beverage packs, very large items like boats, planes, and industrial equipment – especially if being stored outside for long periods of time.
Stretch film is commonly used when products are being secured to a skid. This can be anything from stacked bricks for landscapers to stacked boxes being shipped to a local retail store.
So, besides stretch film and shrink film having different cosmetic characteristics, you now know that shrink film is generally used to protect a product and stretch film is generally used to secure a product to a skid.
Still have questions on which film would work best for your application? Leave us a comment or shoot us a message so our industrial packaging supplies company can discuss recommendations based on your packaging line.
Stretch Wrap Equipment
Stretch wrapping equipment comes in a variety of configurations. We can match you with the right piece of equipment by answering a few questions, or you can browse some of our options by following the links below:
Turntables – Semi Automatic: Requires an operator to bring the pallet load to the turntable and start the machine.
Turntables – Automatic: The operator will bring the pallet load to a conveyor system which then uses photo-eyes to sense the pallet and move it through the wrapping process.
Rotary Arm – Semi Automatic: The operator will take the pallet load to a designated floor area where the rotary arm wraps the pallet. The film carriage moves around the pallet whereas with a turntable, the carriage stays in one place as the pallet rotates.
Rotary Arm – Automatic: Similar to the semi-automatic models except like the automatic turntables an operator will set the pallet on a conveyor system and a photoeye will move the pallet into position to be wrapped by a rotary arm.
Horizontal Wrappers – Semi-Automatic: These are great for long, odd shaped products like 4×4 wood pieces or tires and wraps the products as an operator feeds them through.
Robotic Stretch Wrappers: These machines are positioned by an operator in a loading area and left to wrap the pallet load while the operator can position the next pallet. This is a great option for those that cannot dedicate a single area to a stationary stretch wrapper or need stretch wrapping capabilities throughout a warehouse depending on the job being done.
Stretch Wrap Products
We carry a large variety of stretch film. View an assortment of our options here.
Shrink Equipment
Shrink wrap equipment comes in a variety of configurations just like stretch wrap equipment. L-bar sealers and heat tunnels go hand in hand while other machines can do the whole process automatically. We always welcome questions and recommendation requests – just give us a call and/or browse our options here. Included in our listings are l-bar sealers, heat tunnels, bundling machines, form-and-seal, and sleeve wrappers/bundlers.
Shrink Film
We do not list shrink film on our website as each application requires a look at not only the machine being used but also the products being wrapped. We keep a variety films in stock and ready to deliver. Please contact us so we can discuss options available.
Stretch wrapping equipment comes in a variety of configurations. We can match you with the right piece of equipment by answering a few questions, or you can browse some of our options by following the links below:
Turntables – Semi Automatic: Requires an operator to bring the pallet load to the turntable and start the machine.
Turntables – Automatic: The operator will bring the pallet load to a conveyor system which then uses photo-eyes to sense the pallet and move it through the wrapping process.
Rotary Arm – Semi Automatic: The operator will take the pallet load to a designated floor area where the rotary arm wraps the pallet. The film carriage moves around the pallet whereas with a turntable, the carriage stays in one place as the pallet rotates.
Rotary Arm – Automatic: Similar to the semi-automatic models except like the automatic turntables an operator will set the pallet on a conveyor system and a photoeye will move the pallet into position to be wrapped by a rotary arm.
Horizontal Wrappers – Semi-Automatic: These are great for long, odd shaped products like 4×4 wood pieces or tires and wraps the products as an operator feeds them through.
Robotic Stretch Wrappers: These machines are positioned by an operator in a loading area and left to wrap the pallet load while the operator can position the next pallet. This is a great option for those that cannot dedicate a single area to a stationary stretch wrapper or need stretch wrapping capabilities throughout a warehouse depending on the job being done.
We carry a large variety of stretch film. View an assortment of our options here.
Shrink wrap equipment comes in a variety of configurations just like stretch wrap equipment. L-bar sealers and heat tunnels go hand in hand while other machines can do the whole process automatically. We always welcome questions and recommendation requests – just give us a call and/or browse our options here. Included in our listings are l-bar sealers, heat tunnels, bundling machines, form-and-seal, and sleeve wrappers/bundlers.
We do not list shrink film on our website as each application requires a look at not only the machine being used but also the products being wrapped. We keep a variety films in stock and ready to deliver. Please contact us so we can discuss options available.
Stretch film comes in varying gauges, lengths, chemical make-ups, colors and can be used in numerous applications. Not all stretch film works on all loads and for all applications. One interesting variable and starting point for stretch films is deciding between blown or cast manufacturing processes. But first, if you are unsure of the differences between shrink and stretch start with this blog post.
