Shrink wrap is one of many great ways to protect and transport items. It’s strong, durable, and tamper-resistant.
This article will explain exactly what it is, what it’s made of, the science behind it and its many advantages.
Shrink wrap, or shrink film, is a material made of polymer plastic film used to wrap and package pallets and products.
It is a unique form of plastic packaging as when heat is applied, the film shrinks, forming a tight protective layer around the packaged item.
While both shrink wrap and stretch wrap are used to package and secure products and pallets, their methods are quite different.
While shrink wrap tightens around the packaged item when heated, stretch wrap is wrapped tightly around the packaged item manually, often multiple times, with its elasticity providing the tightness.
There are a number of plastic polymers used to make shrink wrap, offering slightly different properties. The main four are:
Polyvinyl chloride used to be the most commonly used material, as it is lightweight, inexpensive and has a multitude of uses. However, due to a number of reasons, some countries have banned its use, and in countries where it isn’t banned, some major companies have opted to ban it. One of PVC’s issues is that it releases a dangerous odour when heated, with it being advised that this is done in a well-ventilated area. Another issue is the concerns around its sustainability, as in most cases PVC is not recyclable.
Because of these problems, polyolefin (POF) has replaced PVC as the favoured plastic polymer used to make shrink wrap in a number of applications. Polyolefin is extremely durable and versatile and is approved as a food-safe material. Furthermore, Polyolefin is made from 100% recyclable materials.
Polyethylene and polypropylene are types of polyolefin, with polyethylene derived from ethylene. When PE is used to make shrink film, it is often in its low-density form - low-density polyethylene (LDPE). This is because LDPE has high strength, durability, and offers the best quality for printing images and text on the wrap.
Check out our dedicated article to learn more about the differences between PVC, Polyolefin and Polyethylene Shrink films.
To shrink wrap a product, you simply encase and surround it with the plastic film. This can be done manually or by using a shrink wrap machine.
You then need to apply heat to the shrink wrap. This can be done manually using a heat gun, moving the gun around the product until all of the film tightly covers it, or by passing the product through a heat tunnel, which will evenly apply heat around the product, shrinking the film to enclose it.
Now you know the process, how does the ‘shrink’ in shrink wrap actually work?
The molecule chains of polymers are very long, being made up of many monomers (hence ‘poly’). In their natural state, these long chains are randomly intertwined, coiling and twisting around one another with no specific direction or alignment. When these polymers are used to manufacture plastic, the chains are stretched out in lines, becoming untangled.
This plastic is then wrapped around the goods intended to be shrink wrapped, before heat is applied via a heat gun or heat tunnel. When heat is applied to these straight polymer chains, it provides them with energy and increases molecular motion. This motion results in the polymer chains recoiling and shrinking, returning the molecules back to their tangled state as they press around and cover the item being shrink wrapped. When properly cooled, the polymers will remain in this state, maintaining this tight and durable layer, until enough heat is applied to alter it again.
This tangled state is part of what provides the strength and durability of shrink film, as the intertwining and criss-crossing of the chains makes the polymer harder to break apart.
Depending on the item you’re wrapping you may have a number of options available to you. For example, if you need to secure goods on a pallet you may initially opt for “pallet strapping”. However, pallet strapping comes with a number of downsides. It’s easy to overtighten the strapping which can cause damage to the very items they’re supposed to protect (especially fairly “soft” items such as cardboard boxes which can easily have edges crushed by over-tightened strapping). It’s also possible for items to twist free from the pallet if not secured correctly, and strapping doesn’t protect goods from the elements.
Shrink wrap on the other hand offers a number of substantial benefits including:
The tight nature of the shrink wrap ensures increased protection of the encapsulated goods. The item is protected from dirt and debris, as well as having superior moisture protection, and is therefore protected from all the damage these contaminants could potentially cause. Shrink wrap can also include additives such as UV inhibitors, anti-static treatment, and low and non-fusion options for increased protection.
Wrapping goods in shrink wrap gives superior stability to goods when in transit or storage. The tight wrapping ensures the continued rigidity of the pallet or product so there’s no risk of it falling over or items falling out, further protecting items from damage.
Shrink film, especially when made from polyolefin or polyethylene, is tough, durable, tear resistant and puncture resistant. Even with obscure-shaped loads, shrink wrap will not loosen once heated and shrunk. Goods will remain tightly protected and upright when in transit or storage.
Not only is shrink film a relatively low cost, affordable material and form of packaging, it is also a space saver. This tight way of packaging items results in more space available in storage or transit, which could potentially save money when transporting or storing multiple items.
Due to shrink wrapping being tight and secure, it is more difficult for someone to tamper with the goods once wrapped. Furthermore, any tampering would be instantly noticeable as shrink film doesn’t loosen or sag, and isn’t easily tearable. It’s a great way to ensure the sealed items haven’t been tampered with.
No matter the size or shape of the item that is being wrapped, shrink wrapping can do it all. From small, intricate pieces, to large obscure shaped loads, shrink film is a convenient and all encompassing solution for wrapping goods and pallets.
Shrink wrap is perfect for transport and transit as it offers a secure, durable and tamper proof packaging. It’s also great for displaying and protecting consumer items as it can be made see through and printed on.
Some products and industries that utilise shrink wrap are: