Shrink Wrap Buying Guide

Introduction

Using a shrink tight sheeting to create encapsulation and containment around a scaffolding structure is a demanding application that requires a shrink wrap film that has been engineered / designed for purpose. The quality of a scaffold shrink wrap film is determined by the chemical ingredients used and the manufacturing process.

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Much scaffold shrink wrap available today is simply general plastic sheeting that is being branded and sold as ‘scaffold wrap’. However, those selling it simply don’t understand the problems that poor quality can cause for the scaffolders and contractors at the ‘sharp end’. When scaffold sheeting blows off or doesn’t perform properly somebody has to go back and fix it, and that is usually not the person who sold you the shrink wrap!

Buying guide:

• Does the scaffold wrap heat weld & stay welded? (without needing taping.)
• Does the film shrink powerfully? You are looking to achieve a ‘drum tight’ finish with no wrinkles or creases and certainly no thin patches or streaks.
• Does the wrap have the mechanical strength to withstand wind loadings? Ask for a data sheet or specification from your supplier and compare tensile strength and impact tolerance.
• Is the scaffolding shrink wrap properly flame retardant? Ask your supplier for an up to date certificate. Be aware that whilst it can be acceptable to use a film that is flame retardant to the EN standard, some sites will insist on a film that is flame retardant to the more extensive LPS & LPS scheme. Failure to use a BRE approved scaffold cladding may have implications for insurance cover.

What is scaffold shrink wrap made from?

To make shrink film for scaffolding the resin must be a100% fractional melt virgin resin that is not reprocessed / recycled material, with a primary mixture of low density polyethylene (LDPE) and a secondary mixture of linear-low density  polyethylene (LLDPE).

Shrink Wrap Additives

The following additives are used to give scaffold shrink wrap the performance characteristics we need.

Flame Retardancy

There are many flame retardant standards in different countries. In the United Kingdom we use the European EN standard and the LPS/ scheme.

UVI

A light stabilizer (ultra-violet inhibitor/UVI) of the hindered amine gives the shrink film a minimum service life of 1 year. You should be aware that films that if a flame retardant shrink wrap film claims to have a UV stability beyond this it is unlikely to also have enough flame retardancy added as these two additives ‘compete’ with each other.

EVA

EVA (ethyl-vinyl-acetate) additive gives the shrink film flexibility, greater puncture resistance, mechanical strength and deters splitting and brittleness in high winds and extreme cold weather. 

Anti Block

Anti block agent (slip) prevents the film surfaces from sticking together during the manufacturing process and allows for easy unroll/unfold from the roll by the user. Excess or low quality anti-block material will cause the film surface to feel oily and prevent tape from sticking to the surface or film-to-film-fusion. 

Colour additives

Colour additives are used to give the shrink film a white tint that should provide an opacity of at least 65%

Scaffold Wrap Manufacturing Process

The shrink wrap extrusion process starts with the blending of resins and additives. They are melted and blown through a die. After exiting the die the shrink film goes through the air cooling ring and travels up to the guide rolls, where the film bubble is collapsed and flattened and then to the winder where it is rolled on to cores.

The manufacturing process is vital to the following shrink wrap characteristics;

Shrinkage

It may seem obvious, but an important factor in how well a shrink wrap sheeting will encapsulate a scaffolding is how well it shrinks. If a shrink wrap sheet shrinks well, it will fit tightly and it will not flap or ‘chafe’ in high winds. It will be strong.

If you look at the specification sheet of a shrink wrap film you should see that the shrinkage, sometimes known as the ‘shrink ratio’, is described in two ways; Machine Direction (MD) and Transverse Direction (TD). A shrink wrap film should have balanced shrinkage, which means that the shrinkage in both the MD and TD should be similar. However, while most shrink-wrap films have a good shrink ratio % in the Machine Direction (MD) very few have good shrinkage in the Transverse Direction (TD). As well as making the installation process difficult for the shrink wrap installer / end user, a poor shrink ratio may also cause the shrink wrap film to loosen or become slack in the first few days after installation.

So what affects the shrink ratio? It is mostly due to the size of the die from which the shrink wrap film is extruded. At Rhino we use a very small die (700mm) from which the melted plastic polymers are blown into a large bubble of shrink film that has a circumference of 7 metres. This difference between the size of the die and size of bubble, (sometimes called the ‘blow up ratio’), is critical in achieving a powerful shrinkage because when the film is heat shrunk by the end user, around a scaffolding for example, the shrink wrap has a ‘memory’ and will try and return to it’s original size at the point of extrusion.

However, to speed up the manufacturing process most shrink wrap manufacturers use a die that is much larger than we do to manufacture their shrink wrap film. (A larger die has a higher production rate / hour). Typically, a die will be mm to mm wide. This larger die, although making a machine more profitable for the manufacturer, will produce a shrink wrap film with a much poorer shrink ratio, particularly in the transverse direction (TD). So, although our film is a little bit slower to manufacture, by using a smaller die we ensure that our customers get a shrink wrap film that has a shrinkage of 45% in the transverse direction (compared with a typical figure of 10-15% for competitor films). The end result of this is that Rhino shrink wrap is much easier for our customers to install properly, even in tough weather conditions, and once fixed in place is much more resistant to high winds.

Layers

Looking at the specification sheet should also tell you whether the shrink wrap film you are using is a mono (1 layer) film or a multi layer film. In a similar way to ‘die size’, explained above, it is generally more convenient for manufacturers (but not the end user) to supply a multi layered film as it is faster to manufacture and multi layered machines can produce a wide variety of products. However, it can enable unscrupulous manufacturers to ‘hide’ poor quality but cheaper regenerated plastic material within layers. 

A mono layer film is slower to manufacture but it means that any additives, such as flame retardancy, are contained throughout the whole film, and not just the outside layers, and it means we can only use premium resins to manufacture our film.

Thickness

Take a micrometer and measure the thickness of the film in different places. The thickness of lower quality films can vary by as much as 50-75 microns and the result is many points of failure (holes) during the heat shrink process.

Dart Drop

This is a very important measure of the basic mechanical strength of the film, which for scaffold shrink wrapping means the wind loading that the shrink wrap will bear. It is a standard test procedure outlined in ISO-1/2. Compare between alternative films and try and buy a shrink wrap film with the best performance in this area.

Seal Range

The seal range of Rhino shrink wrap film is in the range of 95 to 125 Degrees Celsius. This is an important value because the lower temperature a film requires to seal, the easier it will be to heat weld by the end user. Again, the reason why some shrink wrap films are difficult to heat weld properly is that they have a much higher seal range and this is because many shrink wrap manufacturers add HDPE to their LDPE films, to speed up the production process and make each machine more profitable. However, an film with HDPE added will have a higher weld temperature and so be more difficult for the end user to weld, especially when weather conditions are challenging. It should not be necessary to apply additional strengthening by applying shrink wrap tape to a welded joint between two pieces of shrink wrap film.

Tensile Strength (Yield)

Another test that relates to strength, but with a focus on elasticity - i.e. the ability of the film to return to it’s original form when hit by a force such as the wind. You may notice that scaffold wrapping films with poor elasticity may sag after time, even if they at first seemed ‘drum tight’ when initially installed. This is due to poor tensile strength.

Final Thoughts

Always try and purchase from an ISO accredited supplier, as they will have the necessary quality controls in place to ensure consistency between batches. Always ask your supplier for a specification sheet / data sheet and look closely at the shrink ratio, dart drop and seal range. 

Most shrink wrap plastic film is made in a way that is most convenient for the manufacturer, even if makes life more difficult for the end user. We think it makes more sense to start with the end user and work backwards to make sure the whole manufacturing process is designed to create a film with the desired performance.

Shrink film is an essential packaging material for various industries, from food to pharmaceuticals to manufacturing. Known for its versatility and durability, shrink film protects products from dust, moisture, and damage while providing a clear, attractive presentation. However, with so many types of shrink film available, it’s crucial to know which type suits your needs best. This guide will walk you through everything you need to know about shrink film, including its benefits, types, and key factors to consider when placing an order.

What is Shrink Film?

Shrink film, also known as shrink wrap, is a plastic material that shrinks tightly around a product when heat is applied. It’s commonly used to bundle items together, provide tamper-evidence, and add a layer of protection against external contaminants. Shrink film is available in various thicknesses and materials, each with specific applications and characteristics.

Shrink Film

Benefits of Using Shrink Film

Businesses across many industries rely on shrink film for its wide range of benefits, including:

• Enhanced Product Protection: Shrink film shields products from dust, moisture, and other external factors, keeping items in pristine condition during storage and transportation.

• Improved Aesthetic Appeal: Transparent shrink film allows products to be displayed attractively while offering a tamper-evident seal for added security.

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• Space Efficiency: Shrink film helps save space by bundling items together, making storage and transportation more efficient.

• Cost Savings: Compared to other packaging methods, shrink film is economical and minimizes the need for additional packaging materials.

Types of Shrink Film

Shrink film comes in various materials, each suited to specific uses. Here are some common types to consider when ordering shrink film:

• Polyolefin (POF) Shrink Film: Known for its versatility, clarity, and strength, POF shrink film is commonly used for food packaging and other consumer goods. It’s food-safe, puncture-resistant, and provides a soft yet durable finish.

• Polyvinyl Chloride (PVC) Shrink Film: PVC shrink film is ideal for non-perishable products like boxes, electronics, and other retail items. It’s economical and has good clarity, but it may release odors when heated, so it’s not suitable for food products.

  PVC Shrink Film

• Polyethylene (PE) Shrink Film: Often used for heavy-duty applications, PE shrink film is a thicker material suitable for bundling multiple items together, such as cases of water bottles or large industrial parts.

• Cross-Linked Polyolefin Shrink Film: This type offers extra durability and a high level of puncture resistance, making it ideal for irregularly shaped items or heavy products.

Factors to Consider When Ordering Shrink Film

Choosing the right shrink film involves more than just picking a material. Here are some important factors to keep in mind:

• Product Type: Consider the products you’ll be wrapping. For instance, food items require a food-safe film like POF, while non-food items might be suitable for PVC or PE shrink film.

• Clarity and Presentation: If your packaging needs to be visually appealing, opt for a film with high clarity, such as polyolefin or PVC, for a clear view of the product inside.

• Strength and Durability: Evaluate the weight and shape of your products to determine the thickness and strength of the shrink film needed. Heavier products require thicker, more durable materials.

• Sealing and Shrink Temperatures: Different shrink films require specific temperatures for optimal shrinkage. Make sure your shrink equipment is compatible with the film you choose.

• Environmental Impact: Some shrink films, like polyolefin, are recyclable and environmentally friendly, while others, such as PVC, may have a larger environmental impact. Consider your company’s sustainability goals when selecting shrink film.

Shrink Film Thickness and Roll Sizes

Shrink film thickness is measured in gauge or mils, with thicker films providing more strength. Common gauges include:

• 60 Gauge: Lightweight film suitable for delicate items.

• 75 Gauge: A versatile thickness, suitable for a wide range of consumer goods.

• 100 Gauge: Heavy-duty film ideal for larger or heavier items.

Additionally, shrink film is sold in rolls of varying widths and lengths, allowing you to choose the best fit for your products and packaging equipment.

Shrink Film

Steps to Order the Right Shrink Film

To ensure you choose the right shrink film for your business, follow these steps:

1. Identify Your Packaging Needs: Consider factors like the product’s size, shape, and weight, as well as whether you need food-safe or tamper-evident features.

2. Select the Material: Choose a film type that matches your requirements. For example, POF is ideal for food products, while PE is best for heavy items.

3. Determine the Thickness: Based on the weight and handling of your products, select an appropriate film gauge. Heavier items typically need thicker film.

4. Choose the Roll Size: Calculate the film width and length required for your packaging equipment and desired output volume.

5. Request Samples: Many suppliers offer samples to help you test the film’s performance with your products and equipment before committing to a large order.

Frequently Asked Questions About Shrink Film

Q: Is shrink film recyclable?

Some types of shrink film, such as polyolefin, are recyclable, while others, like PVC, may not be as environmentally friendly. Check with your supplier to confirm if the film you choose can be recycled.

Q: Can shrink film be used for food packaging?

Yes, polyolefin shrink film is food-safe and commonly used for wrapping food products. However, avoid using PVC shrink film for food as it may release harmful chemicals when heated.

Q: What thickness of shrink film should I use?

The thickness depends on the weight and type of products you’re wrapping. For lightweight items, 60-75 gauge is typically sufficient, while heavier items may require 100 gauge or more.

Q: How do I know what size of shrink film roll to order?

Consider the dimensions of your products and the specifications of your shrink wrapping equipment. Measure the width, length, and depth of the product to determine the appropriate roll width and length.

Shrink film offers versatility and durability for various packaging applications. By understanding the different types, thicknesses, and important factors when ordering, you can select the ideal shrink film to protect and present your products effectively.

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