When it comes to shrink wrapping or stretch wrapping a load there are few things to really consider. One what is in the containers like flammables etc, the second is can it be damaged by compression of the wrap, three how do you really want to contain it or could you use banding?
When it comes to protecting products, or holding products together and intact for transport; stretch and shrink wrapping are often employed. Although these two types of wrapping have many differences, they are often confused. This blog aims to outline the differences between the two products and under what application they are both utilized.
And any good warehouse person (guy or gal) worth there salt would be able to tell you this stuff but for today well just use safety as the instructor, and oh did I mention you will need JSA and SWP written up to do the work!
So what safety items did you cover long before we talk about Shrink vs Stretch Wrap? Shrink Wrapping and Strapping Wrapping loads by hand requires you to use circle the load many times, and can lead to dizziness and cause workers to stray into oncoming equipment and traffic. Poorly constructed loads on pallets can collapse, creating lifting hazards or falling on delivery staff or pedestrians.
Whenever possible, use automated wrapping equipment.
If you wrap by hand, use ergonomically correct tools, and rotate to other jobs so that you do not have to wrap too many loads.
Order shrink-wrap on spools that have a wide diameter and are light
Alternate the wrapping direction and techniques.
Fill in hollow inside of loads with air pillows or use shrink-wrap Shippers often bundle or crate items with strapping. The strapping may break and cause injury, especially to the eye. Loose strapping that has been cut off bundles could potentially be a tripping hazard.
When adding strapping, use safety goggles and leather gloves. With heavy strapping, use steel-reinforced gloves. Cut off excess strapping and sharp or pointed ends and remove any broken or damaged bands with metal snips (cutters).
When working with strapped items, face in the direction of the pull. Stay out of the direct line when the strap is under tension. Do not lift a packaged by the strapping.
Before you cut the strapping, anchor the closest end with a holding device. Warn other workers, pick up your snips, turn your back to the strapping and stand out of the line of recoil. Do not remove strapping by breaking it with a hammer, bar, chisel, or other tool.
After you cut the strapping, if the strapping is not made of metal, tie a knot in it. If the strapping is metal, fold and flatten it. Throw out waste strapping immediately so that it does not create a tripping hazard.
Stretch film often is confused with heat shrink wrap. Though often confused, there is a big difference between the two. Below is a quick definition of stretch wrap.
Stretch Wrap– A highly stretchable plastic film commonly made from Linear low-density polyethylene (LLDPE) that is wrapped around items. The elastic recovery keeps the items tightly bound.
Stretch film is commonly used to wrap products on pallets and secure them to each other and the pallet. This often helps to reduce products loss, discourage load tampering, and reduce worker injuryBelow is a breakdown of the two most commonly used extrusion processes of stretch film.
Cast Stretch Wrap- Also called 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 chill roll, where it is quenched and re-solidified. 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. There are both machine grade and hand grade cast stretch film available.
Advantages of Cast Stretch Film- Generally less expensive than blown stretch film, due to reduced manufacturing costs. Increased clarity allows users to see wrapped products. Cast stretch wrap unwinds quietly compared to blown stretch wrap. Cast stretch film offers two sided cling that allows the wrap to stay securely wrapped.
Disadvantages of Cast Stretch Film- Does not offer the load/holding power blown stretch film offers. Cast stretch film has less memory and tear resistance than blown stretch film.
Blown Stretch Wrap– Also referred to as blown stretch wrap, 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. Air is introduced via a hole in the center of the die to blow up the tube like a balloon. On top of the tube an air ring blows onto the film to cool it. This process allows blown film to be tougher and more resilient than cast film. The higher mechanical properties of blown film typically allow a greater load holding power.
Advantages of Blown Stretch Wrap- Offers higher load and stretch capacity. Blown stretch film is a higher quality of film. Blown stretch film has a higher degree of memory once stretched allowing loads to stay better secured. A higher tear resistance is an advantage when securing loads with sharp edges.
Disadvantages of Blown Stretch Wrap- Higher cost due to manufacturing process. Blown stretch wrap has poor clarity due to crystallization in the manufacturing process. Blown film is also noisy when unwound from rolls.
Frequently Ask Stretch Film Questions
When do I use Stretch Film?
Usually stretch film is used to hold boxes and products together on a pallet for transportation. It can also be used to hold other object together and protect objects during transportation and storage. Stretch film can come in a variety of specialty films. Some examples are: UV stretch film, vented pallet wrap, anti-static stretch film, colored stretch film, etc.
How do I know what size of film to use? Different sized thicknesses and widths of film are needed for different applications. Use the chart below to find which thickness and width would be ideal for your application.
Due to rising petroleum costs stretch film manufacturers have been persuaded to make stronger thinner stretch wrap. This thinner stretch film uses less petroleum resin during manufacturing, therefore costs less. The equivalent stretch film uses a multi-layered technology to increase the strength of the film. Different manufacturers have different names for their equivalent films. The two equivalent hand stretch films we offer are Hybrid stretch film and Micron stretch film. We also offer our Performance line of machine stretch film that is thinner stronger and offers users the ability to save on costs. Both hybrid and micron stretch film are considered an eco-friendly option for reducing film waste.
Hybrid stretch film is a thinner stretch film with a super strong resin formula. It is the thinnest strongest film we offer, but is not recommended for loads over 1800 lbs. Because the film is thin, it does not have the same amount of tear resistance as a thicker film.
Micron stretch film is a film in-between the “true gauged” stretch film and the Hybrid stretch film. It is a multi layered film that offers great cling, stretch, and tear resistance. It offers users the ability to reduce costs while staying confident about load security.
Performance machine stretch film is our answer to rising machine stretch film costs. The performance stretch film is a multi-layered machine stretch film that provides more stretch than traditional machine stretch film. It offers a high amount of cling and down sizing opportunity.
Are there any advantages to using opaque stretch film?
Opaque stretch film offers a variety of advantages over clear stretch film. A few advantages include:
- Detours pilferage through valuable shipments by concealing products.
- Helps to protect products from UV Rays.
- Prevents damage caused by rain, dew, and dust.
- Outlasts regular clear stretch film during extended outdoor storage.
- Great for color coding products.
Do I need UV stretch Film?
UV protection can help extend the life of the stretch film when stored in the sun. The use of an opaque UV stretch wrap can increase the storage life of the film and the product when stored outside. Anyone should consider UV stretch for any shipments stored outside longer than 60 days.
Common Stretch Film Terms
Blown Stretch Film- A stretch film derived from the blown extrusion process that has a greater puncture resistance. Click on the stretch film info page to view detailed information about blown stretch film.
Bottom Wraps- The wraps a stretch wrap machine uses to apply film to the bottom section of the load. Forming a strong bottom wrap will help to ensure load stability.
Cast Stretch Film- A stretch film derived from the cast extrusion process. Less manufacturing costs allow cast stretch film to be the more widely used stretch film. Visit the stretch film info page to view detailed info about cast stretch film.
Cling- Allows the film to stick to itself and not the product. Some films have one sided cling and others have two sided cling.
Co-extrusion- Extruding two or more materials through a single die to enable the two materials to merge together.
Dart Drop- A commonly used test to measure puncture strength of a stretch film. It is conducted by dropping a semi-circular shaped object onto the film.
Elastic Recovery-The ability of a stretch film to recover to its original shape after being stretched.
Elmendorf Tear- Another common test used for stretch film and other products to measure tear resistance.
Extruder- Equipment used to change solid polymers into molten polymers.
Film Feed- In a stretch wrap machine, it is the speed at which stretch film is supplied to the load.
Film Force- Refers to the amount of tension applied to the film as the film is applied to the load.
Film Memory- The ability of the film to return to its pre-stretched form. This enables the film to maintain a tight load during transportation.
Film Tail- The start and end pieces of stretch film applied to the load. Generally these pieces are cut off later
Gauge- A measurement used to measure film thickness or caliper. One gauge is equal to .254 microns. Microns are another common form of film measurement.
Gloss- The amount of light reflected from a film’s surface. Cast stretch films tend to have a higher gloss than blown stretch films.
Haze- Refers to lack of clarity in a film. Blown stretch films commonly have more haze than cast stretch films due to crystallization during the manufacturing process.
LLDPE Stretch Film- Linear Low Density Polyethylene stretch film. A plastic that is preferred in a variety of film due to its toughness, stretchability, and relative transparency.
Metallocene- A compound used to make a new form of stretch film. Metallocene stretch films offer increased puncture resistance and many other useful benefits.
Microns- A unit of measurement commonly used to measure the thickness of a film. A micron is equal to one millionth of a meter. One gauge is equal to .254 microns.
Over wrap- The amount of stretch film applied over the top of the load. It is used to provide a downward force on the load.
Pallet Covers- A poly film cover used to protect pallets from dust, UV rays, and conceal the load. Feel free to check out the various pallet covers we offer.
Post-stretch- Stretching a film when wrapping the load to achieve tighter tension on the load
Pre-stretch- Stretching the film before applied to loads. Pre-stretch films can result in improved load integrity and lower packaging costs.
Roping- Bunching the stretch film into a rope shape. Roping used to start many loads and offers an increased strength for additionally securing a load.
Tackifiers- Additives used in the manufacturing process to add cling to the film.
Tear Resistance- Refers to the resistance of the film to tearing forces.
Tension Stretch- A pulling force that stretches the materials
Wide Web Stretch Film- A large sized film used for larger equipment. Generally it refers to machine stretch film wider than 30 inches
Yield Strength- The amount of stretch a film can have without permanently deforming.
Stretch Wrap Equipment
Choosing the right stretch wrap machine should be a careful consideration for any business. There are several factors to consider when making your choice. Below are a few questions to consider.
- How many loads are you currently wrapping and how many loads do you foresee wrapping? This will help to give you a good idea of what equipment to invest in.
- What types of loads will you wrap? Will the loads all be boxes, irregular shapes, fragile, etc. Are the loads heavy, light, stable, unstable, etc. Different machines are used for different applications
- How much do you want to spend? Machines can vary dramatically in costs depending on the features and output capacity require
Even OHSA in the USA covers this feature for safety
There is a right way and a wrong way to pallet wrapping. OSHA (Occupational Safety & Health Administration) has studied and identified potential hazards associated with stretch wrapping your pallet loads. With employee and product safety being critical to your company success, ensure you review and understand the pallet wrapping hazards outlined by OSHA. In identifying these wrapping hazards, OSHA has made suggestions for possible solutions to dealing with these packaging hazards.