When it comes shrink film, temperature restrictions in extreme conditions is an important dynamic to consider. From the temperature that you run your products through the heat tunnel, to atmospheric conditions for your transportation vehicles, temperature matters. In the article below we will explore the role of temperature in relation to shrink film and how it reacts to packaging machinery.
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What Is The Appropriate Range Of Temperatures For Shrink Film Storage?
When storing your shrink film prior to use, make sure that you have a general idea of the best practices for the extremes of both summer and winter storage. During these times of the year, temperature restrictions are of utmost importance for these materials. If shrink film gets too hot, it can melt and stick to itself. If shrink film gets too cold, it can become brittle and crack.
Overall, shrink film is best stored in temperatures between 30 and 77 degrees Fahrenheit. Naturally, summer and winter are the seasons which require you to be most attentive to your storage environment.
Here is an interesting case study done on the use of polyolefin shrink film which was used in several different temperatures for the packaging and preservation of pomegranates. From sciencedirect.com
"The effects of individual shrink film wrapping with two polyolefin films (BDF- and D-955) and skin coating with a sucrose polyester (SPE) Semperfresh on the shelf life and quality of soft-seeded Ganesh pomegranates (Punica granatum L.) stored at 8, 15 and 25°C were studied.
The shrink-wrapped pomegranates could be stored for 12, 9 and 4 weeks as compared to 8, 6 and 2 weeks by SPE coating at 8, 15 and 25°C respectively, whereas non-wrapped fruits could be kept for 7, 5 and 1 week under similar storage conditions.
You can read the rest of the study here.
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How Do You Properly Store Your Shrink Films?
Not Too Hot: During the hot summer months, you want to keep your film in the coolest spot in your warehouse, without being in a refrigerator. This tends to be nearest the floors, on the lowest portion of your pallet-racks. Keep the rolls out of direct sunlight and away from areas in your warehouse that are susceptible to the hot weather outside. Try to schedule your film deliveries early to beat out the sun, and avoid letting them sit in a hot trailer for extended periods of time.
Not Too Cold: If you place your film in a freezer, it may become damaged as well. In some instances where the film has been under extreme cold for too long, problems can occur. For example, PVC film can shatter like glass if dropped, presenting a whole different safety hazard. The goal is to keep the film rolls cool, but not freezing. When packaging frozen foods and other items that must be cooled in a refrigerator, it may be a good idea to use a quality polyolefin film instead.
Sometimes you can catch weather-damaged film before you place it on your shrink wrapper. Watch for:
Sticky Rolls: Not to be confused with those delicious cinnamon buns, sticky film is a warning sign that the shrink film has gotten too much heat. If you have 2 rolls near one another and they are stuck together, don't risk downtime on the packaging line. Find a cool roll to use.
Bagging and Sagging: Film that has seen too much heat before use may have begun to sag on the edges of the roll. Look for unusual issues like this, or bagging on the film before use. Using film that has issues like this can mess up the tracking on your machines, so be alert for damaged rolls, especially in the summer months.
What Temperature Should I Run My Shrink Film At In My Heat Tunnel?
The inside of your heat tunnel is an important dynamic to have locked in prior to packaging your product. The correct temperature for your product depends on which kind of substrate is being utilized. Furthermore, the appropriate heat for your product also depends on the gauge of your shrink film. More often than not, the most typical type of material run through a heat tunnel is 45 - 75 gauge PVC or polyolefin shrink film.
Lets run over a hypothetical situation that will allow you to better understand heat restrictions for your shrink films as they are passing through your heat tunnel. Say you are currently running a 75 gauge PVC shrink film;
An appropriate setting for PVC would be between 215 235 degrees Fahrenheit. Now, if you are going to use a polyolefin film with a gauge of 75, then an appropriate temperature for your heat tunnel would be about 255 275 degrees Fahrenheit. Keep in mind, these are just ballpark figures and depending on the dynamics of your equipment, materials and product, your actual settings may vary.
While these more traditional thicker gauges of film have been used for decades, new advances in technology have produced significantly thinner gauges of shrink film. Thinner gauges currently available include: 35 and 30 gauge. These new cutting edge lower gauge films have excellent strength, a lower carbon footprint and a lower cost. As these films are thinner than traditional shrink films, the temperature restrictions will be different and entirely based upon which gauge of film you choose to employ.
At the end of the day, your conveyor speed is ultimately more important than the temperature of your heat tunnel. Adjusting your shrink tunnel to a lower heat setting and a slower speed (2-3) will increase the life of the tunnel. That being said, all products and packaging lines are case sensitive and it would do you well to work with your packaging machinery and materials vendor to tweak the settings on your machinery and materials. This will ensure that you reach the best possible settings for your particular applications.
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You may occasionally have what you consider to be a particularly sensitive product and are unsure if you should be using a heat tunnel to package your item. Requesting a test of the equipment using heat sensing tapes will allow you to gauge if your product should or should not be packaged with a heat tunnel in the first place. You can get a demonstration like this by reaching out to your packaging machinery and materials vendor and requesting said service.
Conclusion
Depending on the unique setup of your packaging line and the machinery and materials that you choose to run, temperature restrictions are an important element to keep a close eye on. When trying to figure out your best practices in regards to the storage of your materials, take into consideration the storage temperatures you should be using for your films. It is a good idea to work in tandem with your packaging machinery and materials vendor to find the correct temperatures for peak performance.
Lets say you bought the highest-quality shrink film money can buy and stored it away for future use. On a scale of one to 10, how upset would you be if it became unusable or deteriorated into the worst shrink film money could buy? No matter how high-quality the packaging material is, you must take proper precautions when storing it.
Temperature, moisture, dust, and time are all storage factors that can affect the performance and aesthetic of your film. By addressing these few simple storage-related problems, you can improve the look of your product, increase the shelf-life of your shrink film and minimize your long-term costs.
In this article, well detail how the aforementioned factors can degrade the quality of your shrink films and share best practices, highlighting the seasons that have the greatest risks.
Conditions That Affect Your Packaging Materials
Both extremely hot and cold temperatures can affect the condition of your materials over time. Excessive heat can shrink your films, and when running in your machines, they are more likely to jam. It will also become more difficult to package your product with the affected film. Conversely, extreme cold can cause films to become more brittle and increase the risk of cracking.
Dust and other airborne particles can also become problematic. These contaminants can affect your stretch films ability to stretch, and your shrink film's ability to shrink, which could create problems for your machines and your finished goods. Even if your machines have no trouble with the materials, the shrink film can become cloudy and cause trouble with a product that doesn't shine on the shelf as it should.
Lastly, the more time your shrink film sits in storage, the more likely it will suffer from these problems. The longer temperatures fluctuate and other environmental factors can impact your films, the more likely that they become baggy and develop slack edges. When it comes time to wrap your final product, you may find out that the wrapping process will either take longer or produce far too much waste.
Best Practices for Storing Shrink Film
Before purchasing and storing shrink film or any other packaging material, make sure you know its storage requirements. You dont want to try to work with climate-compromised packaging. Your supplier should have this information available if youre 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 which require you to be most attentive to your storage environment.
Summer Storage
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. Youll 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, especially in the summer. That way, the materials wont 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 youll also give yourself more time to store them before the temperature reaches its peak.
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Winter Storage
As we noted above, packaging films tend to become especially brittle in cold temperatures, which greatly reduces its stretching and shrinking properties. While the PVC may crack, it can even shatter like glass if left in extremely-cold conditions for too long. Surely you didnt expect your shrink film to present a safety hazard.
As in the summer, store your rolls away from doors to avoid temperature fluctuations. You also want to ensure rain or snow wont create unwanted moisture in the rolls. If youve 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.
How to Identify Damaged Rolls
When you take shrink film out of storage, you may not know how to tell if its 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 its 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 youre purchasing, take the time to assess how youll store them to ensure they protect and present your product exactly as youve planned.
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