Overview of the detection and control technology o

Overview of flexible packaging detection and control technology (I)

I. current situation and development trend of flexible plastic packaging industry

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

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, in the next five years, drug packaging will become the second largest economic growth point of flexible packaging. The sales volume and sales volume of other industrial packaging and health care products, including soap, cosmetics, disposable products and other retail packaging, have increased rapidly. In a word, plastic flexible packaging has covered a large number of markets with its unique characteristics of bright colors, novel patterns, low price and convenient use, and has penetrated into every part of the manufacturing field

at present, the competition in the flexible packaging industry is becoming increasingly fierce, and all regions have played their regional advantages to improve the quality of products. At present, Shantou tensile testing machine has formed innovative characteristics. The tensile testing machine is a new data testing machine head that separates electronic technology from mechanical transmission, and the flexible packaging base led by Yuyao, Zhongshan, Taizhou, Tongcheng, Xiongxian, Dongguang, etc. the packaging factory actively introduces and develops new packaging materials, In order to meet all kinds of packaging needs. But there are also the following problems:

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

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

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

4. The utilization rate of testing equipment is not high. When doing tests, only experimental reports are given, and a large number of tests are less carried out for process. However, in the later stage of research, there is also the phenomenon of purchasing testing equipment to visit customers in response to superior inspection

therefore, China's flexible plastic packaging industry should actively develop projects with high technical content, such as the development of environmental friendly, thin, special multifunctional flexible packaging materials; Actively introduce international standards and foreign advanced 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 to actively play 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, plastic, widely listened to the experience and practice of local production, industrial chain extension, deep processing and other aspects, aluminum plastic and other multi-layer composite packaging materials are becoming more and more extensive, and the quality problems of their composites are also becoming increasingly prominent. After the composite material is processed into a bag, the composite layer is likely to cause damage if it is exposed to the harsh environment or the influence of moisture and chemical composition. Therefore, the higher the composite strength of flexible packaging, the better. Tearing or destruction is the most ideal. High viscosity sum value can prevent the separation of composite layer. Using 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 money, 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 is 30.0 ± 0.2mm wide and 150mm long. Used for artificial leather, woven composite bags, etc

1.2 sample preparation

remove 50mm from both ends of the sample 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 substrate 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, immerse one end of the sample about 20mm in a suitable solvent for treatment, and then 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 obtained directly

2 state adjustment and test environment

the sample should 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 should be carried out in the above environment

3 test speed selection

a method 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 (ldm-100, 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 and the tensile direction are T-shaped, as shown in Figure 1. Start the testing machine, which displays the force value and the stripping force curve in the stripping process of the sample 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 experimental report is as follows

6.1 determine the use of adhesive according to the measured force value, and select the appropriate adhesive, such as 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

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

6.2 choose different materials for compounding, pet/pe, pet/cpp, ny/pe, etc.

6.3 understand the uniformity of composite film compounding according to the fluctuation of the displayed curve; Analyze the stability of this group of samples through 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 common problems in testing

7.1 when the composite film is used for T-Peel test, the sample to be tested will always turn up or swing down. It is difficult to form a right angle when the sample is fixed by hand and moved with the pull-down of the sample. How about peel strength? Is it accurate that this test-bed is mainly used for dynamic change fatigue tests of various torque bearing parts

in fact, gb/t clearly stipulates that "the T-shaped peel test of bonding flexible materials and flexible materials is to apply peel force on the unglued end of the sample to make the sample peel along the adhesive wiring, and the angle between the applied force and the adhesive wiring need not be controlled", that is, to test the force value in a free state, and it is not necessary to control the angle

7.2 composite products compounded with aluminum foil. When doing the peel test, due to the poor mechanical properties of aluminum foil, During the test, it breaks as soon as it is pulled, and its peel strength cannot be tested. It is unrealistic and accurate to describe the peel strength by saying that it cannot be peeled. Its strength is not so high that it cannot be peeled. Sometimes, it is used to stick adhesive tape on the surface of aluminum foil, and then take samples for type peel test, but the force value data displayed is much higher than that of the sample without adhesive tape. How to deal with this kind of situation to accurately reflect the peel strength of composite products

in fact, GB clearly stipulates that "plastic is compounded on plastic or other substrates (aluminum foil, paper, etc.) According to the measurement principle of various soft composite plastics, the composite layer and the substrate shall be pre peeled 50mm along the length of the pattern, and the peeled part shall not have obvious damage. If the sample is not easy to peel off, immerse one end of the sample for about 20mm in the solvent for treatment. After the solvent is completely volatilized, conduct the peel test. If it cannot be separated from the substrate after this treatment, the test cannot be carried out. ". 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 far greater than the tearing force of the aluminum foil itself

as an enterprise, it studies its peeling force, and makes experiments 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 this kind of peel strength. Different kinds of substrates have different modulus, and the modulus of the substrate affects the energy required when the substrate deforms, thus affecting the peel strength. It increases with the increase of the thickness of the substrate. Therefore, when discussing the peel performance of this kind of 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 for three-layer or multi-layer composite product structures, such as BOPP printing/pe/vm CPP, sometimes the peel strength of the first or second layer is detected, and the first or second layer is pulled off at the same time, so the peel strength between the detected layers is not true and accurate. What is the way to avoid this situation? When testing three or more layers of composite structures, is there any regulation on which layer to start from and what is the order

international standards have no clear provisions on this, so the results of such tests should not only indicate the peel strength, but also indicate the phenomena occurred in the test process. 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 it is not allowed to peel all layers on the same sample at the same time for testing, and the peeling of multilayer composite film shall be subject to the intermediate layer