Source: Link Testing Instruments Co.,Ltd.
Tea contains catechins, cholestene, caffeine, inositol, folic acid, pantothenic acid and other ingredients, which can improve human health, and tea has a certain fragrance. Because it is prone to deliquescence in a high-humidity environment, resulting in the loss of aroma and the deterioration of tea leaves. Therefore, tea production enterprises generally use plastic composite film, aluminized composite film, aluminum-plastic composite film or iron cans for packaging, so as to protect the tea, so that the tea fragrance is not easily lost and the tea is not easy to deliquesce and mold. Therefore, ensuring the overall sealing performance of tea is one of the basic requirements for the packaging of finished tea products. If the sealing performance of the packaging is poor, in the circulation links such as sales and transportation, it is easy to cause the finished tea packaging to lose its fragrance and the packaging is loose and not tight.
Test methods and instruments
The domestic test method standard for the sealing performance of flexible plastic packaging is mainly GB/T 15171-1994 "Test method for sealing performance of flexible packaging". This test uses the LTY-01 leak tester independently developed by Link Testing. LTY-01 leak tester is professionally suitable for sealing test of packaging bags, bottles, tubes, cans, boxes, etc. It can also test the sealing performance of the test piece after the drop and pressure test.
Test principle: LTY-01 leak tester is designed according to the test principle of testing packaging sealing by negative pressure method. The equipment is mainly composed of vacuum tank, microcomputer operation panel, vacuum pump and other components. A certain amount of water is injected into the vacuum tank. By placing the sample in the water in the vacuum tank, and using the vacuum pump to evacuate the vacuum tank, the test is carried out. There is a certain pressure difference between the inside and outside of the sample. If the sealing performance of the sample is poor, the gas inside the sample will overflow to the outside along the weak seal on the surface of the sample under the action of the pressure difference, showing a continuous flow. Bubbles pop out. Alternatively, the sealing performance of the sample can be judged by observing the recovery of the shape of the sample after expansion and release of the vacuum.
Test samples and test procedures
Test sample: packaging of finished tea products of a certain brand.
Experimental procedure:
(1) Immerse the finished tea packaging sample in the water of the vacuum tank.
(2) Close the sealing cover, and set the test parameters such as the vacuum degree to be achieved in the test and the pressure holding time in the vacuum tank through the microcomputer operation interface.
(3) Turn on the vacuum pump and press the start test button on the operation panel to start the test.
(4) Observe whether there are continuous bubbles on the surface of the sample during the vacuuming process and pressure holding process. If there are continuous bubbles, record the pressure value displayed by the equipment when the bubbles appear and the specific position of the bubbles on the surface of the sample.
Test Results and Analysis
Among the 5 finished tea packaging samples tested, all samples had air leakage at the lower sealing edge when the temperature was -57.8 ~ -62.1 KPa.
From the above results, it can be seen that the products all have air leakage at the lower sealing edge, and the manufacturer should adjust their heat sealing parameters appropriately to ensure good overall sealing performance. In this paper, the use of LTY-01 leak tester can accurately test the pressure value of packaging air leakage, and there is no human interference, which helps enterprises to strictly control the packaging quality, and can effectively reduce the probability of poor sealing of finished packaging to the market.
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