Stretch Film vs Shrink Wrap

Stretch film or shrink wrap?

 As a packaging material, stretch film is often commonly confused with shrink wrap; These two are different, however.

Stretch film is wrapped tightly around pallet loads, packages, or objects to secure them together or keep them protected. Shrink wrap, on the other hand, is applied by first covering the item loosely; heat is then used on the shrink wrap, causing it to shrink tightly around the package.

Which one do I need?

If what you need is to hold loads together for transportation or storage, stretch film packaging will be the best solution for you. On the other hand, if your priority is to protect or bundle small loads together, shrink wrap will work better. Shrink wrap is also widely used for covering food items such as cheese or meats.

Types of stretch films

Stretch film comes in different widths, lengths, gauges, hand grades, and machine grades. Enhanced versions of stretch film use higher alpha-olefins that make them more resistant to punctures and breakage. They also come in specialty variants such as colored stretch film, UV stretch wrap, and anti-static stretch film.

The size and type of stretch film packaging you select will depend directly on its intended application. There are four different classes of stretch film: Cast film, blown film, pre-stretch film, and high-performance film. All of these films are available in hand and machine grades.

1. Cast Stretch Wrap

Cast stretch wrap, is manufactured using a cast extrusion process. The Cast extrusion process is a continuous process by which a thermoplastic material is melted and extruded through a flat die onto a cooled roller which solidifies the film.

This process allows the Cast stretch film to have excellent clarity, require less force to stretch, increased tear resistance, unwind quietly from machines, and offer a superior cling.

Advantages of Cast Stretch Wrap:

• Less expensive than blown stretch film.
• Due to reduced manufacturing costs cast stretch film is more popular. Increased clarity allows users to see wrapped products.
• Cast stretch wrap unwinds quietly compared to blown stretch wrap.
• Offers one-sided cling that allows the wrap to stick to itself without causing too much friction with nearby wrapped pallets.

Disadvantages of Cast Stretch Wrap:

• Cast stretch film has less memory and tear resistance than blown stretch film on average. However, new technologies have recorded cast films with the highest tear resistances ever recorded.

2. Blown Stretch Film

Is manufactured using the blown extrusion process. This plastic melt is extruded through an annular slit die, usually vertically, to form a thin-walled tube. Then, air is introduced from an opening in the center of the die to blow up the film tube like a balloon. On top of the film tube, an air ring blows onto the film to cool it.

This process allows blown film to be more robust and more resilient than cast film. The higher mechanical properties of blown film typically allow a more significant load holding power, however, nano-technology blended cast films utilizing LLDPE, HDPE, and PP have recorded higher load holding force and containment force.

 Advantages of Blown Stretch Wrap

• It offers higher load and stretch capacity.
• Blown stretch film has a higher degree of memory once stretched, allowing product loads to stay better secured.
• Blown films typically have higher tear resistance, which is an advantage when securing loads with sharp edges. 

Disadvantages of Blown Stretch Wrap

• Higher cost due to the manufacturing process.
• The blown stretch wrap has poor clarity due to crystallization in the manufacturing process.
• Blown film is also noisy when unwound from rolls.  

3. Pre-Stretch Films

It is made as a co-extruded Blown Film, where It is stretched close to its ultimate break point prior to being wound onto rolls for its final use. What this means is that the film does not require as much stretching energy as a standard stretch film to achieve the same wrapping force. It also has excellent puncture resistance and is easier to apply than conventional blown and cast Films. 

The resulting rolls are generally light and easy to handle, reducing operator fatigue. Since there’s very little torque involved, users also benefit by being able to use a walk-forward wrapping technique, which can help prevent slip and fall incidents. 

Advantages of Pre-stretch film 

• Better load stability with less product, less physical energy, and greater control.
• Pre-stretched film consumption can be less to one half that of traditional stretch film. This creates a cost savings of anywhere from 25% – 40%.
• The roll is lighter (about 2/3 less than traditional film) and easier to manage. It is about half the thickness and double the strength.

  4. Performance stretch film

Due to rising petroleum costs, stretch film manufacturers have made stronger, thinner stretch wrap. This thinner stretch film uses less petroleum resin during manufacturing, therefore costs less. These films are commonly referred to as “equivalent stretch film” because they will be made as a 63 gauge or less, but perform like a cast or blown 80 gauge, for example.

Performance stretch film uses a multi-layered technology to increase the strength of the film. The performance stretch film is a multi-layered stretch film that provides more stretch than traditional machine stretch film. It offers a high amount of cling and downsizing opportunity.

Advantages of Performance Stretch Wrap

• Offers higher load and stretch capacity (up to 400%).
• Substantial cost-savings compared to their higher-gauge, blown, and cast alternatives.
• More eco-friendly – uses less pounds of film per pallet wrap and therefore, less ends up in our landfills and/or oceans.

Disadvantages of Performance Stretch Wrap

• Higher cost per roll when compared to a blown or cast alternative of the same gauge.
• If not being used on the right equipment, or on the correct setting – the film will not perform as intended.
• Does not perform as well on older machinery with no pre-stretch capabilities. 

Types of Shrink Film

1. PVC (Polyvinyl Chloride)

PVC is one of the most common plastics produced in the world. It was previously the most used shrink film until the introduction of other shrink films. Common PVC shrink wrap uses are CD and DVD packaging, software, and other non-edible items.

Advantages of PVC Shrink Film

• Cost advantage – PVC is much more affordable than other shrink films
• Low temperature to shrink
• Tear resistant – PVC shrink film is less likely to rip or tear than the other alternatives

Disadvantages of PVC Shrink Film

• Sensitive to temperature change – cold makes it brittle and heat makes it wrinkle
• Releases harmful fumes – proper ventilation is needed when working with PVC shrink film

2. POF (Polyolefin) Shrink Film

Polyolefin materials are available with different characteristics, including cross-linked wrap that provides high-tensile strength and great clarity. POF shrink wrap has taken the place of PVC shrink wrap in many applications.

Advantages of POF Shrink Film

• High clarity appearance and versatile making it great for a number of applications
• Puncture and temperature resistant – making it better for binding multiple items
• FDA approved for contact with food

Disadvantages of POF Film

• More expensive than PVC Film
• Has come machine compatibility issues

3. PE (Polyethylene) Shrink Wrap

Polyethylene is a single monomer wrap that is formed with the addition of ethylene during polymerization. PE shrink wrap is a heavy duty shrink film that is commonly used for larger commercial items.

Advantages of PE Shrink Film

• Recyclable – out of the three types mentioned this is the only recyclable option
• Not as limited to thickness as other shrink wraps – making it great for larger scale projects
• Thicker, tougher, and more stretchable than the others shrink wraps

Disadvantages of PE Shrink Wrap

• Harder to shrink out completely and requires more cooling space
• More expensive than other options
• Lower clarity

Whether you are looking for stretch film or shrink film, Korpack is ready to help you choose the product that is best suited for your operations. If you want to know how we can help with your packaging needs, contact us today.