Testing and Research on the hottest soft plastic c

2022-07-23
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With the rapid development of food, cosmetics, medicine and other industries, as well as the continuous improvement of packaging materials and processing technology, flexible plastic packaging is playing an increasingly important role in many fields

for example, in the food industry, it is predicted that in 2003, the sales of flexible plastic packaging will exceed 56% of the sales of packaging processing, of which the bagged meat food will grow the fastest at the rate of 20% per year. In addition, according to the 99 annual industrial report published by the business and Economic Research Institute affiliated to the Washington flexible packaging Association, the pharmaceutical packaging will become the second largest economic growth point of flexible packaging in the next five years. The sales volume and sales volume of other products such as industrial products packaging and health care products packaging, including soap, cosmetics, disposable products and other retail packaging, are growing rapidly. In a word, plastic flexible packaging has covered a large number of markets with its unique characteristics, such as bright colors, novel patterns, low prices, easy to use, and has penetrated into every part of the manufacturing field

at present, the competition in the flexible packaging industry is becoming more and more fierce. Various regions have given full play to their regional advantages to improve the quality of products. At present, Shantou, Yuyao, Zhongshan, Taizhou, Tongcheng, Xiongxian, Dongguang and other flexible packaging bases have been formed. Packaging factories actively introduce and develop new packaging materials to meet various packaging needs. But there are also the following problems:

1 As a whole, the market competition is becoming increasingly fierce, especially in the low-end products. They compete to hold down prices, resulting in vicious competition. The products with high performance and high added value are not only few, but also of low quality

2. The standards of packaging products within the industry are implemented differently. International and industry default standards coexist with international standards, which is relatively chaotic. Some enterprises even have no awareness of standards. There are no standards for some new processes and materials

3. The existing quality testing equipment is backward, and the price of imported quality testing equipment is high. Many enterprises are in a dilemma

4. The utilization rate of testing equipment is not high. Only the test report is given for the test, and a large number of tests are less conducted for process research. There is also the phenomenon that the purchasing of testing equipment provides customers with a visit to cope with the inspection of the superior

therefore, China's flexible plastic packaging industry should actively develop projects with high technical content, such as the development of environmental friendly, thin and special multifunctional flexible packaging materials; Actively introduce international standards and advanced foreign standards, speed up industrial standardization, and improve the overall level of our products and the ability to participate in international competition; Actively develop advanced quality testing equipment to replace expensive imported products; It is worth discussing how to give full play to the role of flexible packaging industry associations, communicate information, improve quality awareness and exchange advanced experience

II. Composite strength test and control application of flexible plastic packaging composites

single plastic packaging is becoming less and less. In order to expand the use of products, the price and quality of multi-layer composite impact machines such as plastic, aluminum and plastic are in direct proportion. Packaging materials are becoming more and more extensive, and the problem of composite quality is becoming increasingly prominent. After the composite material is processed into a bag, it is likely to cause damage to the composite layer when exposed to harsh environment or the influence of moisture and chemical composition. Therefore, the higher the composite strength of flexible packaging, the better. Tearing or damage is the most ideal. High viscosity sum value can prevent the separation of composite layer. The use of high viscosity adhesive will undoubtedly achieve high-quality composite, but the production cost will increase. It can not only achieve the required composite, but also save the cost, which requires the detection and analysis of the quality of the composite layer in order to find the appropriate composite factors. The following is the discussion of test methods:

1 sample preparation

1.1 sample size

a method width 15.0 ± 0.1mm, length 200mm. For composite films, etc

b method has a width of 30.0 ± 0.2mm and a length of 150mm. Used for artificial leather, woven composite bags, etc

1.2 sample preparation

remove 50mm from both ends of the sample in the width direction, and evenly cut 5 longitudinal and transverse samples along the sample width direction. The composite direction is longitudinal

peel the composite layer and base material 50mm in advance along the length of the sample, and the stripped part shall not have obvious damage. If the sample is not easy to peel off, immerse one end of the sample about 20mm into a suitable solvent for treatment, and conduct the peel force test after the solvent is completely volatilized. If the composite layer cannot be separated from the substrate after this treatment, the test cannot be carried out and the test report can be directly obtained

2 state adjustment and test environment

the sample shall be placed in an environment with a temperature of 23 ± 21 ° C and a relative humidity of 45%-55% for more than 4h, and then the test shall be carried out in the above environment

3 select

a method for test speed 300 ± 50mm/min

b method 200 ± 50mm/min

4 test steps

clamp the two ends of the stripped part of the sample on the upper and lower clamps of the testing machine (ld-500, Beijing landmaker) respectively, so that the longitudinal direction of the stripped part of the sample coincides with the center line of the upper and lower clamps, and the tightness is appropriate. During the test, the UN stripped part is T-shaped with the tensile direction, as shown in Figure 1. Start the testing machine, which displays the force value and the stripping force curve in the process of sample stripping in real time

5 at the end of the test, the arithmetic mean value will be calculated automatically according to the curve shape obtained from the test, with Newton (n) as the unit

6 the test report is as follows

6.1 determine the use of adhesives according to the measured force value and select appropriate adhesives. For example, the performance comparison of several adhesives of Beijing GAOMENG company

project yh501sl yh501s (1) imported adhesive D (1)

peel strength ≥ 31 2 1.. 6

100 ° boiling difference

it can be seen from the test data that the performance of yh501sl is better than that of yh501s (1) and imported rubber D (1), which is suitable for plastic composite

6.2 select different materials for composite. Pet/pe, pet/cpp, ny/pe, etc.

6.3 know the uniformity of composite film composite according to the fluctuation of the displayed curve; Analyze the stability of this group of samples by curve superposition

6.4 adjust the workshop humidity, solvent moisture content, composite film hardness, film surface treatment degree, machine tension control, production speed, composite pressure and other production processes based on the data

7 solutions to common problems in testing

7.1 when conducting T-type peel test for composite film, the sample to be tested will always turn up or swing down. It is difficult to form a right angle when fixing the sample by hand and moving with the sample. How is peel strength accurate

in fact, gb/t clearly stipulates that "T-type stripping test for bonding of flexible materials and flexible materials is to apply stripping force on the unglued end of the sample to make the sample peel along the bonding wire, and the angle between the applied force and the bonding wire need not be controlled", that is, to test the force value in a free state without controlling the angle (as shown in Figure 1)

7.2 for the composite products compounded with aluminum foil, due to the poor mechanical properties of the aluminum foil during the peel test, it is impossible to test the peel strength when pulling, and it is unrealistic and accurate to describe the peel strength by saying that it is impossible to peel. Sometimes, the adhesive tape is pasted on the surface of the aluminum foil, and then the sample is taken for the type peel test, but the displayed force value data is much higher than that of the sample without adhesive tape, How to deal with such cases to accurately reflect the peel strength of composite products

in fact, GB clearly stipulates that "enterprises of plastic packaging materials can make further improvement and promotion by reference to the following aspects: materials are compounded in plastic or other base materials (aluminum foil, paper, etc.) According to the measuring principle of various soft composite plastics, the composite layer and the substrate shall be pre peeled for 50mm along the length of the pattern, and the parts similar to the shape of the load deformation curve shall not have obvious damage. If the sample is not easy to peel off, immerse one end of the sample about 20mm into the solvent for treatment. After the solvent is completely volatilized, conduct the peel test. If the sample cannot be separated from the substrate after such treatment, the test cannot be conducted. ". In such cases, it can be concluded that the test cannot be carried out according to international regulations, indicating that the peeling force between the substrate and the aluminum foil is much greater than the tearing force of the aluminum foil itself

as an enterprise to study its peeling force, the test was carried out after pasting adhesive tape on the surface of aluminum foil. The results can be used as a reference to measure the quality of the composite film through comparison. A large number of studies have shown that the substrate has a certain impact on the peel strength. Different types of substrates have different moduli, and the modulus of the substrate affects the energy required for the deformation of the substrate, thus affecting the peel strength. It increases with the increase of the thickness of the substrate. Therefore, when discussing the peel performance of such products, it is necessary to note the type and thickness of the substrate, the type and thickness of the adhesive tape used, Otherwise, the test data will lose reference value

7.3 three layer or multi-layer composite production the increasing number of sports events in the world will drive the demand structure of sportswear. For example, BOPP printing/pe/vm CPP sometimes tests the peel strength of the first or second layer and pulls the first or second layer off at the same time. In this way, the peel strength between the detected layers is not true and accurate. What can be done to avoid this situation? When testing three or more layers of composite structures, is it specified which layer to start from and what is the order

there is no clear stipulation in the international standard. Therefore, the results of such tests should not only indicate the peel strength, but also the phenomena during the test. According to a large number of tests, the peel strength of each layer of multilayer composite film is different, and there is no relevant national regulation. Enterprises can formulate enterprise standard test methods according to their own actual situation. The general principle is that each layer shall not be peeled off at the same time on the same sample for test, and the peeling of multi-layer composite film shall be subject to the intermediate layer

(to be continued)

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