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How to reduce the breakage ratio of flexible package for food at low temperatures?

Apr 24,2020

Source: Link Testing Instruments Co., Ltd

Some food or pharmaceuticals need to be stored in extremely low temperature (sometimes the ambient temperature is required to be as low as -18℃) to guarantee the quality of the products.

However, the mechanical properties e.g. impact resistance of those flexible packaging materials used for those products may be compromised when the products are stored at an extremely low temperature. As a result, the package may become liable to be broken in storage or transportation.

Therefore, it is necessary to ensure the low temperature resistance of the packaging materials before use them to pack the products mentioned above. The low temperature resistance of the packaging material is mainly reflected by its flexibility and impact resistance. To be specific, the packaging materials must have sufficient flexibility and impact resistance so that the package can resist the impact caused by external forces during storage and transportation process and the breakage ratio of those packaging bags may be reduced.

This article provides a simplified test method of the impact resistance of flexible package for your reference. The test specimens are plastic bags for frozen food. The testing instrument used for the tests is Link Testing’s LTJM-06 Pendulum Impact Tester. In the tests, two groups of specimens which have been conditioned in standard conditions and at -18℃ respectively are tested and the low temperature resistance can be obtained by comparing the test data of the two groups of specimens.

Figure 1. LTJM-06 Pendulum Impact Tester

The tests shall be performed according to the following procedures.

(1) Cut Specimens

Cut 20 pieces of specimens from provided samples. Condition the specimens at 23±2℃, 45% ~ 55%RH for at least 4 hours. The size of the specimen shall be 10cm x 10cm.

(2) Measure Thickness

Measure the thickness of specimens. Make the center as the point to be measured. The final result should be the average value of the results of all the 20 pieces of specimens.

(3) Condition Specimens

Select 10 random specimens and condition them at -18℃ for 2 hours.

(4) Calibrate Instrument

Select proper impact head and impact range, which shall be within 10% to 90% of the full test range of the instrument. For the tests we did, we select Φ12.7 mm impact head and the diameter of the clamped specimen is Φ89 mm. The impact energy is 3 J. The instrument shall be calibrated as required.

(5) Test at Room Temperature

Clamp the specimen. Step on the pneumatic pedal switch to clamp the specimen tightly. Click Test so that the impact head will be released and impact the specimen. The result will be automatically displayed in the screen. Repeat the operation until all the 10 pieces of specimens are tested.

(6) Test at Low Temperature

Test the specimens which are conditioned at low temperature in the same way as described in step 5.

The low temperature resistance of the packaging materials shall conform to certain requirements e.g. the low temperature resistance of BOPA/LDPE composite film should be not less than 60%. Otherwise, the user or manufacturer shall consider how to strengthen the mechanical properties of those packaging materials at low temperature.

For more details about LTJM-06 Pendulum Impact Tester, please visit

About Link Testing Instruments Co., Ltd:

Link Testing Instruments Co., Ltd is one leading supplier of packaging testing instruments, which is headquartered in Jinan, China