As one kind of packaging material that is widely used, shrink label is featured with compactness, transparency, decency and high bonding strength. If the shrinkage ratio of the shrink film is too high, the printings on the shrink label may be twisted and deformed. If the shrinkage ratio of the shrink film is too low, the shrink label may not be able to stick to the bottle tightly. Therefore, it is necessary to control the shrinkage ratio of the shrink films that are used in shrink labels so as to maintain a good appearance of the bottle and reduce the production cost.

This article provides a simplified test method for shrinkage ratio of shrink labels for your reference. The sample material is shrink label made from PVC and the testing instrument is Labthink’s C631H Film Thermal Shrinkage Tester.

Figure 1. Shrink Labels of Beverage Bottles

The testing instruments for film thermal shrinkage test on the market mainly employ drying oven or liquid bath to process the testing materials and then measure the size after heat shrinking to calculate the shrinkage ratio wherein only shrinking force can be measured. Labthink’s C631H Film Thermal Shrinkage Tester conforms to ISO 14616, which can measure both shrinking and contracting force of heatshrinkable films.

Before tests, Cut 20 pieces of 15mm wide specimens along the machine direction and transverse direction of the samples of shrink labels, respectively. Divide those specimens into 10 groups, 2 specimens for each group. The length of the specimens should be proper so that the valid specimen length between the sample grips should be not less than 100mm. Measure the thickness of the specimen and calculate the average value of at least 3 points. Use special hole puncher to make two holes in the specimen so that the specimen can be mounted easily in the sample grips.

After preparing the specimens, the tests can be started in the following procedures.

1)     Mount the specimens. One specimen in one group should be mounted in the load cell and no force should be applied on the load cell. The other specimen in the said group should be placed horizontally between the support arm and the displacement sensor with valid length of 100mm.

2)     Set reference temperature for PVC shrink film, test temperature and end temperature, etc. Start test.

3)     Set thermal shrinking temperature. When the temperature inside the heating chamber reaches the preset value, the specimen should be delivered to the heating chamber. The specimen shrinks and the load cell and displacement sensor will record the real-time shrink force and shrinkage ratio.

4)     If the maximum shrink force appear after 15 seconds to 30 seconds since the test starts, record the maximum shrink force and shrinkage ration. Otherwise, adjust the setting of shrinking temperature and do the test again.

For more details about C631H 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.

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 14616.

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.

(5)   When the preset temperature of heating chamber 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 shrinkage ratio 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.

More details  about Labthink, please feel free to contact Shirley Wu via:

• Labthink at CHINAPLAS 2011: Booth S21, Hall 1.1

Labthink will participate Chinaplas 2011 at Booth S21 Hall 1.1 during 17~20, May in Guangzhou (China Import & Export Fair Pazhou Complex). We will bring new technology and products of Packaging Quality Control Testing Techniques to each visitor.

Labthink is willing to further strengthen exchanges with professionals of the plastic and rubber industry, and brings more professional information and services with her profound testing control techniques. Labthink(Booth S21, Hall 1.1), inviting and await for your presence respectfully.

For more details, please feel free to visit http://www.labthink.cn

or contact Shirley Wu via:
EMAIL: trade2@labthink.cn
SKYPE: shirley-labthink
MSN: shirleywu_labthink@hotmail.com

More about Labthink:

Labthink focusing on the laboratory testing instruments R&D and production and laboratory IT services, is dedicated to provide professional quality control solutions for customers in packaging, food, pharmaceutical, medical, daily chemistry, printing, adhesive, automotive, petrochemistry, bioscience, construction, new energy and other industries.

Labthink is an international enterprise headquartered in Jinan, China with administrative, sales and service branches in Shanghai, Guangzhou,Brussels and etc.,covering over 40 countries and regions.

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CHINAPLAS –Asia’s No.1 International Plastics and Rubber Trade Fair

Accompanying the growth of China’s plastics and rubber industries for nearly 30 years, CHINAPLAS has become a distinguished meeting and business platform for these industries and has also largely contributed to their prosperous development. At present, CHINAPLAS is not only the largest plastics and rubber trade fair in Asia, but also widely recognized by the industry as the 3rd most influential exhibition in the world. Its significance is surpassed only by K Fair in Germany, the world’s premier plastics and rubber trade fair, and NPE in USA, the second largest plastics fair in the world.

But, deformation cause by high shrinkage rate is a problem for ordinary flexible cigarette package. Generally, the shrinkage rate is controlled within 3%-7%. For heat shrinkage testing of BOPP cigarette film, ASTM D 2732 is applied. Take Labthink PARAM RSY-R2 Film Free Shrink Tester as an example; mark the vertical and crosswise lines on the specimen with clear indication of direction. Put the specimen in between the frame, and immediately emerge into 120±2C constant temperature medium for 20 seconds. Then, emerge the specimen into the prepared normal temperature bath for 5 seconds, and take it out. Lay horizontally and measure the vertical and crosswise size within 30 minutes. The measurement should be with accuracy up to 1 mm. At present, some companies heats 1 minute, 5 minutes or other conditions under 120C with different testing results.

For more details and whole quality control project for BOPP Films, please feel free to contact Shirley Wu via trade2@labthink.cn or (tel)0086-531-85061080.

More about Labthink:

Labthink, focusing on laboratory testing instrument R&D, production and laboratory IT services as the core business, is dedicated to provide perfect and professional product quality control solutions for customers in packaging, food, pharmaceutical, medical, daily chemistry, printing, adhesive, automotive, petrochemistry, bioscience, construction, new energy and other industries.

Labthink is an international enterprise headquartered in Jinan, China with administrative, sales and service institutions in Shanghai, Guangzhou and Brussels as well as other over 40 countries and regions.

Labthink, as a knowledge-base enterprise, advocates scientific research and combines production with IT services. Labthink is devoted to share the most excellent testing technologies and the most advanced IT achievements with customers worldwide. Labthink instruments are now operating in more than 5000 laboratories of authoritative institutions and renowned enterprises. Labthink IT service, with the innovative online cloud computing information management mode, promotes the informationization trend of Laboratories!

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