Abstract: This paper introduces the detection method of flexible packaging and its important influencing factors. At the same time, it combines the needs of the market to give a detailed explanation of the new development and new application of detection technology. Keywords: leak, seal, packaging, storage, broken bag
There are many indicators to consider when choosing flexible packaging and flexible packaging materials, such as the barrier to light, gas, the size of the headspace, the cost of packaging, the cost of transportation and storage, the ease of use, the environmental friendliness of materials, etc. . The comprehensive scoring of these indicators is the basis for selecting the optimal packaging, and the sealing test (or the sealing test of the sample after the aging test, vibration test and other simulation tests) is a veto in the soft package evaluation. Because the sealing property is the premise of realizing the functionality of the packaging, it is also a comprehensive reflection of whether the selected flexible packaging materials are matched with each other and the selected packaging form in terms of mechanical properties, thermal properties and optical properties. Poorly sealed packages can cause deterioration of the product due to the ingress or egress of gas or liquid, and may also cause pollution to the environment or surrounding objects. For functional packaging, leakage will also result in loss of packaging functionality and serious consequences for the user. Loss.
Temperature influence factors and development trends of flexible packaging sealing test
1. Flexible packaging sealing test method
Commonly used methods for detecting leaks are positive pressure method and negative pressure method. The positive pressure method increases the internal pressure by filling a gas into the sample, and then judges whether or not a leak occurs according to a change in the internal pressure of the sample. The negative pressure method is to place the sample in the water in the test chamber, and by vacuuming the test chamber, the sample immersed in water is subjected to internal and external pressure difference, and the gas overflow in the sample or the infiltration of water into the sample is observed. This determines whether the sample has a sealing defect. The test data of the tightness of the flexible packaging is an important basis for condition setting and evaluation of the results in the simulation tests such as storage, stacking and vibration.
Compared with other testing items, the biggest characteristic of the sealing test is that it is very rich in the types of testing objects, while the other testing objects are often single. For example, the tensile test can only detect the film or sheet, and the flaw test can only detect. The film and headspace test can only detect the package, and the seal test can not only test various packages but also test the semi-finished products. The samples can be just finished production or in any part of the circulation process. Sampling, while using test accessories, can also expand the types of samples that can be inspected and further relax the limitations on the shape and size of the sample.
2. Factors affecting the tightness of flexible packaging
The soft package sealing is a comprehensive reflection of whether the selected flexible packaging materials match each other and the selected packaging form in terms of mechanical properties, thermal properties and optical properties. External force, temperature change, light radiation, etc. can directly affect the tightness of flexible packaging. In addition, there are some factors that may not directly affect it, but it will lead to lower material strength, heat seal layer fastness, and soft packaging material additives. Problems such as oozing, which in turn will affect the tightness of the flexible package. However, it must be noted that the specific impact of each influencing factor on different packaging forms and packaging materials is inconsistent. If the impact of each influencing factor on the tightness of flexible packaging is to be analyzed one by one, the workload of testing will be greatly increased. And cost, so we can hardly take into account all the influencing factors in the actual test, but the particularly prominent factors must be considered, and should even be reflected as one of the test conditions, otherwise the practicality of the test results will Subject to restrictions.
Practical experience has shown that temperature is a key factor affecting the sealing of flexible packaging during its manufacture and subsequent storage and transportation. On the one hand, for the heat-sealed flexible package, the suitability of the heat-sealing temperature directly affects the strength that the seal can withstand, and the flatness of the bag may also affect the actual sealing effect of the flexible package due to heat deformation. On the other hand, for flexible packaging that has already been produced, the ambient temperature still has a non-negligible effect on its sealing properties, because the currently widely used flexible packaging materials are composite films, and some even consist of high polymers, metals, and paper. Three or more materials are composited, and different materials often have different thermal properties. After the external ambient temperature changes, the difference between the expansion coefficients of the material may cause the interlayer to separate or deform, or cause the strength of the material to decrease, so that the strength of the soft package seal will also drop greatly, so many flexible packages are The sealing performance under high temperature or low temperature conditions is much lower than the test data in the normal temperature environment, and the resulting package leakage is not uncommon. Therefore, when testing the tightness of flexible packaging, we should pay attention to the impact of changes in ambient temperature. It is necessary to control the temperature of the samples subjected to the sealing test and achieve the actual detection at a specified temperature.
3. New changes in seal detection
Nowadays, various new types of packaging have been introduced to the market, but the detection requirements for the tightness of flexible packaging have not only been reduced, but have become more important than ever, because the more expensive the packaging, the less likely it is to cause functional failure of the packaging due to leakage, whether in brand image or cost. In addition, enhanced testing means that packaging tightness is critical. In order to meet the needs of this market, the sealing test equipment has greatly improved in terms of test condition control and detection accuracy.
First of all, it is a sealing inspection device with a temperature control function. As mentioned earlier, the change in ambient temperature during testing does have a significant impact on the results of the seal test. In fact, the effect of temperature on the tightness of the flexible package has also attracted the attention of packaging designers, especially the current long distance. The transportation of goods makes many commodities undergo significant temperature changes from the completion of production until the consumer uses them. Some products undergo temperature fluctuations in circulation, and some products are stored at high or low temperatures. It is not uncommon for a package to pass the test in a laboratory environment but leaks during actual use. Now we can pre-process the sample by controlling the change of the temperature environment or control the temperature in the test chamber to achieve accurate detection of the tightness of the flexible package. However, since the temperature change and the pressure change in the package are both simultaneous, it is still passed. It is more practical to control the test data obtained by simulating the temperature in the test chamber to simulate the actual environment. At present, we have been able to achieve the uniform temperature control of the test chamber temperature from room temperature to 60 ° C, which can meet the storage environment simulation requirements of most commodities.
Secondly, improve the accuracy of detection and quantify detection indicators. The leak test is a destructive test. It is impossible to test all the products. Therefore, it is very important for the seal test to obtain accurate and effective test data with limited samples. However, in the past, when the seal test was conducted, only the pass and fail conclusions could not provide more effective and more valuable data. Therefore, when the actual storage and transportation environment is slightly harsh, the number of leaked packages may be obvious. increased. Now we can use the positive pressure test equipment to accurately measure the maximum burst pressure of flexible packaging samples, and also accurately determine the maximum time that flexible packaging samples can be pressed without breaking under the specified pressure, and can also be achieved through test accessories. The sealing test of the specified position of the sample effectively enhances the practicability of the test data, and can assist in analyzing the weak links in the packaging structure, providing a basis for improving the packaging structure, selecting a more suitable packaging material, and stacking, storing, transporting, Test models such as impact provide more accurate critical conditions for damage.
4 summary
As an important testing item for flexible packaging, the sealing inspection equipment has been greatly improved in the control environment control and detection accuracy, and the practicality of the sealing inspection data has been enhanced, so that it can be used to improve the flexible packaging structure and select flexible packaging materials. A bigger role. In the future, with the diversification of flexible packaging forms, the flexible packaging sealing detection technology will certainly have further development, and in conjunction with other testing indicators to play a greater role in the evaluation of flexible packaging.