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Monitoring method for impact resistance of plastic shopping bags

Jan 13,2021

Source: Link Testing Instruments Co.,Ltd

Plastic shopping bags are important tools used by consumers to store the purchased goods, and have the function of carrying, which provides great convenience for consumers' purchase activities. Plastic shopping bags are generally vest bags, which are currently divided into three categories: ordinary plastic shopping bags, starch-based plastic shopping bags and degradable plastic shopping bags. The most common are ordinary plastic shopping bags, which are made of polyolefin. As the main raw material, such as LDPE, HDPE, LLDPE, mLLDPE, etc., it is made by adding appropriate fillers, such as calcium carbonate, so this type of shopping bag cannot be degraded; starch-based plastic shopping bags and degradable plastic shopping bags are made of modified starch, Completely degradable plastics are the main raw materials, so these two types of plastic bags are degradable and cause little pollution to the environment. As the plastic shopping bags currently used in China are still mainly non-degradable ordinary plastic shopping bags, discarded plastic bags have become the culprit of "white pollution". In order to reduce the burden on the environment, in addition to responding to the country’s "plastic limit" call to minimize the use of plastic shopping bags, and increase the number of repeated uses of plastic bags to reduce the use of plastic bags. The realization of this measure requires plastic shopping bags to have good impact resistance. Avoid early damage to the plastic bag during use and affect its service life.

Test method and instrument   The test standard that can be referred to for the dart impact test of plastic film and sheet is GB/T 9639.1-2008 "Test Method for Impact Resistance of Plastic Film and Sheet, Free Falling Dart Method Part 1: Step Method". The test equipment used in this test is the LTMC-A falling dart impact tester independently developed and produced by Link Testing Instruments Co.,Ltd

Falling Dart Impact Tester LTMC-A

The test principle of the instrument: At the beginning of the test, select the appropriate initial mass of dart and counterweight according to the thickness and material of the sample. During the test, the falling dart freely drops the impact sample. If the sample is damaged, reduce the weight of the falling dart by △m; if the sample is not damaged, increase the weight of the falling dart by △m, and then change it with The mass of the falling dart impacts the sample again, and the mass of the falling dart is increased or reduced according to the test results, and so on, and the test is repeated. In short, the use of weights to increase or decrease the mass of the dart depends on whether the previous sample was damaged. When the test of 20 specimens is completed, calculate the number of damaged specimens N, if N is equal to 10, the test is completed; if N is less than 10, continue to add specimens for the test until N is equal to 10; if N is greater than 10, It is still necessary to continue to supplement the sample test so that the undamaged number of the sample is 10. Then the equipment automatically calculates and displays the impact damage quality of the sample according to the calculation formula in the standard.

Test sample and test process Test sample: This test uses a plastic shopping bag provided by a supermarket as the test object. Experimental procedure:

  • Turn on the switch of the instrument and select Method A or Method B as required. Method A was selected for this experiment.
  • Adjust the falling height of the falling dart to 0.66 ± 0.01 m, and adjust the adjustable bracket of the equipment so that the falling dart can impact the center of the sample after falling.
  • More than 20 specimens with a size of at least 18 cm × 18 cm are randomly cut from the sample surface.
  • Take one piece of the sample and place it on the lower clamp, make sure the surface of the sample is flat, step on the foot switch, the device will automatically clamp the sample.
  • Obtain the approximate impact damage quality of the sample through the pre-test, then insert the falling dart of this quality into the magnetic connector vertically, click the test option, the falling dart will automatically fall and impact the sample.
  • Input the damage condition of the sample into the equipment, and use the weight to increase or decrease the mass of the dart according to the damage condition of the sample.
  • Repeat (4) ~ (6) until the damaged or undamaged quantity of the sample meets the requirements, and the equipment automatically calculates and displays the impact damage quality. Test results and analysis   

Test results and analysis.

 The impact damage mass of the plastic shopping bag sample tested this time is 107.4 g. While providing convenience for consumers, plastic shopping bags have a bad impact on the environment we depend on for survival. By monitoring the performance of plastic shopping bags, increasing the number of times they can be used is an effective way to reduce the burden on the environment and has good impact resistance. Performance is one of the properties that plastic shopping bags should have. This article uses the LTMC-A falling dart impact tester to test the impact resistance of the plastic shopping bag samples. The test process is simple, there is little human interference, and the test results are accurate.

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