NEWS

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.

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. Frozen Food

The tests shall be performed according to the following detailed procedures.

• Cut 10 pieces of specimens along the width direction of the provided sample material. The size of the specimen shall be 100mm by 100mm or the diameter of the specimen shall be 100mm. Then condition the specimens in an environment where the temperature is 23±2℃ and the humidity is45% ~ 55%RH for at least 4 hours. Note: The tests should be performed in the same environment.
• Measure the thickness of each specimen from its central point. Calculate the average value of the 10 results and record it as the specimen thickness.
• Select the impact head size according to the impact energy, which shall be within 10% to 90% of the full test range of the instrument.
• Calibrate the instrument as required by the user guide.
• Spread the specimen and clamp it tightly. Make sure the specimen is free of creases. Do not stretch the specimen too tight. The same surfaces of the 10 specimens shall be impacted.
• Fix the pendulum and then release the pendulum to impact the specimen. Record the displayed value.
• Cut another 10 pieces of specimens along the width direction of the provided sample material. The size of the specimen shall be 100mm by 100mm or the diameter of the specimen shall be 100mm. Then condition the specimens in an environment where the temperature is -18℃ for at least 2 hours. Then repeat the procedures from step 2 to step 6.
• The low temperature resistance can be obtained by calculating the ratio of impact energy at -18℃to the impact energy in standard condition. The unit of low temperature resistance is %.

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 www.linktesting.org

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.