How to test the shrinkage properties of shrink film used for ...

Source: Labthink Instruments Co., Ltd

Click here to get more.

Shrink wrap, also shrink film, is a material made up of polymer plastic film. When heat is applied, it shrinks tightly over whatever it is covering. It is very common to see shrink film is used to pack bottled drinks such as beers, mineral water and beverage, etc. Such kind of packaging is featured with good flexibility, tear resistance, impact resistance and durability. Common raw materials used for shrink films include PE, POF and PET, etc.

The shrinkage properties of shrink film may directly influence the performance of the packaging. Those properties include shrinkage ratio, shrinking force, contracting force. To be specific, if the shrink film is low in shrinkage ratio, shrinking force and contracting force, it may not be able to cover the goods tightly. On the other hand, if the shrinkage ratio, shrinking force and contracting force of the shrink film is too high, the goods within the packaging may be deformed due to the compression caused by the shrink film.

Therefore, proper shrinkage properties are important to the shrink packaging for bottled drinks and it is necessary for the manufacturers to test the shrinkage properties of the shrink films before use. This article provides a test method of the shrinkage properties of shrink film for your reference. The test specimen we used are shrink films used for one brand bottled mineral water and the testing instrument we used for the tests is Labthink&#;s FST-02 Film Thermal Shrinkage Tester.

Figure 1. Shrink Film used in Bottled Drinks

Labthink&#;s FST-02 Thermal Shrinkage Tester conforms to ISO .

Figure 2. FST-02 Thermal Shrinkage Tester

The tests should be performed according to the following procedures.

(1)  Cut six pieces of specimens from the machine direction and transverse direction respectively. The specimen width should be 15mm. Make two holes in the two ends of the specimen with special hole puncher. The distance between the two holes should be 100mm.

(2)  Divide those specimens into three groups, one from machine direction and one from transverse direction for each group. For each group, one is used for shrinking force and contracting force tests, the other one is used for shrinkage ratio test.

(3)  Clamp one group of specimens in the sample grips with load cell and displacement sensor. Keep the specimens straight.

Figure 3. How to clamp the specimens

(4)  Set test temperature, end temperature and other test parameters. Click Start Test to start the tests.

If you are looking for more details, kindly visit Cell Instruments.

(5)  When the preset temperature of heatingchamber is reached, the specimen will enter the heating chamber automatically. The system starts countdown, records and displays the real-time force values and displacement changes. When the test is finished, the heating chamber stops heating and the specimen will be sent out of the heating chamber. The contracting force will be measured.

(6)  When the test is finished, the maximum shrinking force, maximum contracting force and maximum shrinkageratio will be displayed automatically.

(7)  Repeat the operations of step 3 to step 6 until all the specimen tests are finished.

(8)  The test results of the specimen for machine direction and transverse direction should be the average values of the three groups of the results.

For more details about FST-02 Film Thermal Shrinkage Tester, please visit www.labthink.com

About Labthink Instruments Co., Ltd:

Labthink Instruments Co., Ltd is one leading supplier of packaging testing instruments, which is headquartered in Jinan, China and operated in Boston, U.S.A.

Using a generous amount of shrink-wrapping film might seem harmless or even the right thing to do. Better to overestimate, than underestimate when it comes to sizing, right? Wrong! Over time, you may experience shrinking profits as your materials costs increase. In fact, it&#;s better to simply get it right the first time.

Nailing down your shrink film measurements is easier than you might think. Finding the proper film width and length will depend on what type of film you are using. You will need to know a few facts and measurements before calculating your shrink film dimensions. In this article, all measurements are in inches.

• Orientation/flow through shrink tunnel (This will inform which side is your product length vs your width)
• Type of machine (this will dictate what type of film you need)
• Production/Conveyor Speed
• Product dimensions (always round up to the nearest inch)
  • Width: parallel to the cut-off or cross seal
  • Length: parallel to the fold of the film, in cases of centerfold film
  • Height: In cases of products with uneven surfaces, the height should be considered from the bottom to the highest point of the package

The most common forms of shrink wrap film are tubing, centerfold film, and shrink wrap bags. Conveniently, there is a formula to calculate the proper measurements for each kind.

Centerfold: Combine the height and the width of the item, then add 2-3 inches of wiggle room. (3 for larger items only). The formula for this is H+W+2.

Tubing: Tubular shrink film is typically only used for oblong objects. To determine the width of your shrink film tube, multiply the circumference of your object by 1.15, then divide your total by 2. In other words, (CIR×1.15)÷2. As for the length of your shrink wrap tube, simply add 2-3 inches to the length of the object.­

Shrink Bag: For most applications, bags are the most beginner-friendly solution to shrink wrapping. They are already sealed on 3 of the 4 sides, which makes packaging your item simpler.  To find the right width for your shrink bag, follow this formula: (CIR×1.13)÷2. As with our previous examples, the length of your shrink bag should be the length of your object, plus 2-3 inches.

Every application is different and finding the right size film can be even more difficult when your item is an irregular shape. When in doubt, ask an expert. Every service technician at Best Packaging is trained in shrink wrapping procedure. During your next visit, ask a technician to take a look at your shrink wrapping line and your product to get a shrink film recommendation.

What&#;s your take? We welcome guest bloggers! if you&#;d ever like to collaborate.

Contact us to discuss your requirements of film free shrink tester. Our experienced sales team can help you identify the options that best suit your needs.