Below are 7 characteristics that detail some functions of shrink film. These are important to consider when using it for your product packaging.
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This is typically measured in PSI, and tells you the amount of force that the shrink film will exert on your product. If you're packaging a multi-pack that needs to be tightly contained without damaging, understanding your shrink force is very helpful, especially for adjusting your shrink machinery accordingly. If the shrink force is high and you're packaging wood, this won't matter.
However, if you are packaging a small stack of paper or lightweight chipboard boxes, this could matter. Historically, polyolefin films are high shrink force films. Polyvinyl chloride (PVC) films have low shrink force. New polyolefin formulations offer reduced amounts of shrink force.
Shrink films are either bi-axially oriented or preferentially oriented. Bi-axially oriented films shrink equally in both directions (Machine Direction or Cross Direction).*
Preferentially oriented film shrinks differently in either direction. The benefits of a preferentially oriented film include using less film and preventing product distortion.
In addition to altering your shrink percentages by using preferentially oriented film, you can also lower the shrink percentage and stay with a bi-axially oriented film e.g. 40/40 30/30, 20/20.
Another related characteristic is Free Shrink. Unfortunately, this isn't a tip to get free shrink wrap, but it's just as important. I know, I know... Free shrink is the amount of shrink-ability in a film before it makes contact with your product. High levels of free shrink allow you to get a better-looking package on difficult shapes and sizes.
This measures how hard it is to actually break the film, and how hard it is to tear the film once it has been punctured.
Often, films with high resistance to puncture have lower resistance to tear and vice versa. If you need to make this trade-off, select the characteristic that is more important (e.g., if you have a window box, puncture resistance is very important). Choose a shrink film that balances the security of your product with ease of access to the actual product. Be sure to keep your shrink wrap stored in a cool (but not too cool) storage area to prevent any weakening of the film prior to use.
This characteristic is a measure of how much moisture will or will not travel through the film.
If low moisture transmission into or out of your package is important, you should pay attention to this characteristic for improved shelf life. Something you will want to consider for this and to reduce or eliminate fog is modified atmosphere packaging.
Antifog films are used on food (fresh and frozen) to mitigate moisture build-up on the film.
The moisture can cause a fog that affects the viewing of the product through the film. (If I'm buying something, you bet that I'm skipping over the fogged-up package for the one with the product I can actually see).
Odor barrier films are used to prevent unacceptable odors from either traveling into or out of your package. Don't disappoint your customers after they've purchased your product with a foul smell. Enough said.
It's important to identify some specifics about your product to be packaged before diving into the details of the films available to you. Without question, a packaging supplier is key to selecting the appropriate film for your needs. Their industry experience and ability to understand your needs gives them the expertise to ascertain which types of films will and won’t work for your product.
Some of the packaging considerations you’ll need to be aware of include:
With so many types of flexible packaging film available, you are sure to find the right packaging for your product. Whether you need an option with a high melting point, one that emphasizes durability, or one that prioritizes recyclability and sustainability, there is a shrink film product available to suit your needs. With all of the opportunities for a custom finish to any product, it’s always important to do your research and consider your specific needs to determine the best options.
Also, you’ll need to do some homework regarding equipment. If you have an automatic shrink wrapper or are planning to purchase one in the future, it’s important to keep an eye on your bag length and running speeds. Sometimes operators adjust the bag length from the original specs to make running the line easier. This is particularly more noticeable on older pneumatic shrink wrap equipment. Running your film at just 1" larger than necessary can equate to 2,000 extra feet of film used per day. That’s approximately 118 wasted rolls of film.
Be sure to think about how capable your internal maintenance technicians are. Adding a shrink film wrapper to your packaging line will require technical support on a regular and as-needed basis. Assess your internal maintenance team’s comfort level with working on the new machine(s), and make sure you have a backup technician for when service is needed and your internal team can’t handle the repair.
Before purchasing and storing shrink film, make sure you know its storage requirements. You don’t want to try to work with climate-compromised packaging. Your supplier should have this information available if you’re unsure what your material requires. Overall, shrink packaging is best stored in temperatures between 30 and 77 degrees Fahrenheit. Naturally, summer and winter are the seasons that require you to be most attentive to your storage environment.
Your facility will likely be subject to high heat in the summer, if not during springtime. If shrink sleeves are kept in temperatures exceeding 100 degrees, they may prematurely shrink and compromise their ability to protect your goods. During these hot months, keep your shrink materials stored in the coolest areas of your facility without subjecting them to refrigeration.
They should be kept cool, but not too cold. The coolest spots in your warehouse are typically close to the floors – on the lowest part of your pallet racks – and away from windows or places that are subject to a lot of sunlight. You’ll also want to keep your shrink films away from high-traffic doors because the temperatures in these areas tend to fluctuate greatly.
Additionally, try to schedule your shrink film deliveries early in the day. That way, the materials won’t sit in the back of a hot trailer when traveling from warehouse to warehouse. Not only will you avoid the harshest hours of the sun, but you’ll also give yourself more time to store them before the temperature reaches its peak.
As mentioned, packaging films tend to become especially brittle in cold temperatures, which greatly reduces their stretching and shrinking properties. While the PVC may crack, it can even shatter like glass if left in extremely cold conditions for too long.
As in the summer, store your rolls away from doors to avoid temperature fluctuations. You also want to ensure rain or snow won’t create unwanted moisture in the rolls. If you’ve been using PVC shrink film to package frozen foods or other products that spend time in a freezer truck or refrigerator, consider switching to a polyolefin film. This is a more durable, food-safe, and recyclable material that will keep your package intact during transit and packaging.
When you take shrink film out of storage, you may not know how to tell if it’s been compromised. One key sign is sticky rolls. If PVC rolls stick together, they were likely exposed to too much heat. Don't risk downtime on the packaging line by trying to use them anyway. Skip over the rolls that are stuck together. Bagging and sagging are also signs of overheated film. The rolls may begin to sag on the edges or show bagging within their layers. Using these rolls can interfere with the tracking on your machines, so avoid using these compromised rolls as well.
Remember, even the highest-quality shrink film and packaging materials are apt to deteriorate when subject to these environmental factors. No matter what quality film rolls you’re purchasing, take the time to assess how you’ll store them to ensure they protect and present your product exactly as you’ve planned.
Finally, keep your target audience at the forefront of your packaging design. The type of material you choose is a part of your brand, so any disconnect between that and your brand’s message will confuse consumers and make them lose trust. To appeal to your customers, you have to research and understand them enough before you make these key marketing and branding decisions. Market research is a great way to learn what your target audience values and decide how to pair those details with your budget, transportation, and sustainability needs and goals. Always listen to your key demographic and cater to their needs specifically.
For a quick look at some additional considerations regarding your use of shrink wrap film, check out this free shrink film cheat sheet.