Quality inspection and control technology IV of th

2022-07-30
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Quality inspection and control technology of flexible plastic packaging IV

v. tightness inspection of flexible plastic packaging

the tightness of flexible packaging is also an important performance index, especially in food, pharmaceutical packaging, daily chemical and other industries. The tightness will directly affect the quality of products. Poor sealing is the main cause of leakage and corruption in the future. The test methods are:

coloring solution immersion method

is usually applicable to composite bags with little air content

the method is to take out the contents of the sample, wipe the inside of the sample, pour the test liquid (colored aqueous solution with obvious color difference with the filter paper) into the sample area, and seal the mouth. Place the sample on the filter paper for more than 5min and observe the leakage of test liquid from the sample. Then turn over the sample and test the other side

water punching method

is usually applicable to composite bags with more air content

the most commonly used method is to use the sealing tester (mfy-01, Beijing landmark) with the following characteristics

1 The advanced vacuum generator is used to form a stable air source from positive pressure to negative pressure, so as to avoid the disadvantages of traditional vacuum pump such as pulsation and high impurity (oil) content

2. The high-precision electronic pressure sensor displays the vacuum degree in the test vessel in real time, which is automatically controlled by microcomputer. The short plate of new energy endurance mileage for test participants needs to be supplemented (vacuum degree, holding time) can be set at will

refer to gb/t for the test method, put an appropriate amount of distilled water in the vacuum chamber, and then immerse it in water. At this time, the distance between the top of the sample and the water surface shall not be less than 25mm. Cover the sealing cover of the vacuum chamber and adjust it to one of the following values respectively; 20. 30, 50, 90kpa, keep the vacuum for 30s

the vacuum value set shall be determined according to the characteristics of the sample (such as the packaging materials used, sealing conditions, etc.) or the provisions of relevant product standards. However, the specimen shall not be cracked or the sealing part shall not be cracked due to the excessive internal and external pressure difference of the specimen

during the test, pay attention to the leakage of the sample during the formation of vacuum and the vacuum holding period, and observe whether there are continuous bubbles. The occurrence of isolated bubbles is not considered as leakage

the quality of the packaging bag is measured through the determination of the tightness, and then the rationality of the packaging process is determined

VI. testing and control of ink layer combination fastness of flexible plastic packaging printing

in many types of printing, flexible packaging printing such as plastic film, cellophane, composite film, etc. accounts for a large proportion. With exquisite printing and novel design, the outer packaging will undoubtedly win more favor from consumers. However, due to transportation friction, handling, storage time and other reasons, this kind of outer packaging may cause the ink layer to fall off and affect the overall appearance. Consumers may think it is a "fake and shoddy" commodity, boycott the purchase, or even complain. As a result, the reputation of the manufacturing enterprise was seriously damaged

the traditional test method is to stick the tape on the sample, then peel it off manually, and judge the ink layer bonding fastness based on experience. Due to uneven bonding, the stripping force is different each time, and it varies from person to person, so the comparability is not strong, so it is very strong to control this quality

disc peeling tester and adhesive tape rolling machine (blj-01a, ygj-01a) can accurately measure film printing products, completely avoiding human factors. The standard tapes required for this test are as follows:

width 20mm, adhesion n/20mm, tape substrate cellophane, adhesive natural rubber, solvent aromatic hydrocarbon. The results are only meaningful if standard tape is used. The test method is as follows:

1 Take 250mm × For 30mm sample, the place with uniform ink color shall be taken as far as possible to facilitate the measurement results

2. Gently stick the adhesive tape meeting the above requirements on the sample, and the sample shall be flat and true without wrinkles, so as to avoid bubbles as far as possible

3. Place the test sample with adhesive tape on the roller press, start the test, take down the test sample after rolling back and forth for three times, and put it aside for five minutes. This process makes the adhesive tape and the sample bond evenly, and it still has high impact strength at (4) 0 ℃ to drive away bubbles

4. Manually pre strip 80mm of the sample to be tested, fix both ends on plate A and plate B respectively, start the test, and separate the tape from the sample

5. Take down the sample and cover the uncovered part with 20mm wide mm grid paper. Count the number of cells occupied by the ink layer and the number of cells occupied by the removed ink layer respectively. Calculate according to the following formula:

ink layer bonding fastness =a1 (a1+a2) × 100%

a1: the number of cells of the ink layer

a2: the number of cells of the removed ink layer

according to the regulations, 95% of the ink layer bonding fastness is qualified

common problems of users in the actual operation of the test are solved:

1 After stripping, the sample is torn and the test results cannot be recorded. At this time, the strength of the sample shall be considered, provided that the tape strictly meets the international requirements

2. The calculation of test results is troublesome, and all stripped parts shall be calculated. In case of high thermal conductivity and conductivity or both, cover the place with MM grid red at the most serious peeling according to experience, and calculate 10 × The inner part of 10 cells is enough

3. No matter how carefully the sample is made, there are always bubbles between the adhesive tape and the sample, which will undoubtedly affect the test results

it is actually caused by uneven coating of adhesive tape, although it meets the requirements (n/20mm). Qualified enterprises had better use a testing machine with a drawing device that can automatically record the stripping load to screen the tape and try to avoid errors

the above tests of flexible plastic packaging, but the income after completion is a clear and predictable indicator. In actual production, it is very important to adjust the production process and improve the product quality. Through continuous tests, we can master various reasonable production parameters to make the production quality stable and reliable

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