What is the thickness of the soft bag?

1, the importance of film thickness uniformity is one of the prerequisites for materials to have specific protective functions. Taking barrier functional materials as an example, whether the barrier layer is uniform or not will directly affect the overall barrier performance of the materials. The barrier layer is the most important layer in the barrier film. On the one hand, the barrier performance of the barrier film depends on the choice of barrier layer materials (for example, the barrier layer of materials with excellent barrier performance is mostly aluminum foil, aluminum plating, silicon oxide plating, PVDC, EVOH, etc.). ); On the other hand, it depends on the thickness of the barrier layer. Generally, the greater the thickness of the barrier layer, the better the barrier performance of the film. However, when the thickness of the barrier layer reaches a certain level, the barrier performance of the film tends to be stable and will not increase with the increase of the thickness of the barrier layer. High barrier materials are expensive, so the thickness of the barrier layer directly affects the overall cost of the barrier film. The application of multilayer composite film can effectively reduce the packaging cost, in which the thickness of the barrier layer is only about 10% of the overall thickness of the film, and some even only 5μm (or less), but it is very difficult to control the thickness of the barrier layer. If the thickness uniformity of the barrier layer is not good, the functional weakening of the barrier layer will easily occur, which will lead to the instability of the barrier performance of the whole film, and the barrier performance of some packages may be poor, which will lead to the failure to reach the due shelf life of the products. Moreover, the change of the barrier layer thickness of some films (especially those with good transparency) will also affect the overall appearance and color of the films and reduce the display of goods. Whether the film thickness is uniform or not will also increase the difficulty of film printing and the corresponding use process. Taking gravure printing widely used in China as an example, the control of printing tension is very important to ensure the quality of printed matter. The control of tension is related to the material, thickness and thickness uniformity of the film, and poor control will directly lead to inaccurate material overprinter. In addition, poor film thickness uniformity may also lead to winding dislocation after printing. In the process of making multilayer composite film, the non-uniformity of any film layer will cause the non-uniformity of subsequent processing and make the thickness uniformity of the finished film worse. When the film with uneven thickness is used as the outer packaging, the mechanical properties of the packaging are prone to weakness. If the packaging is impacted by external force in the process of packaging, transportation, storage and sales, these weak points are prone to cracks and holes, which will reduce or completely lose the special preservation function of materials. 2. How to detect the film thickness In the film manufacturing and processing industry, detecting the film thickness is one of the most common film detection indicators, and thickness detection can be divided into two categories: film thickness detection and coating thickness detection. Because the thickness of the film is the sum of the thickness of each layer of resin, if the overall thickness uniformity of the film is poor, the thickness distribution of each layer of resin will be different. Undoubtedly, the detection of coating thickness will be more conducive to effectively controlling the thickness uniformity of each layer of the film. However, for multilayer films, if we want to accurately measure the thickness of each layer, we need to invest a lot of corresponding thickness detection equipment, which will increase with the increase of film layers, bringing greater economic burden to enterprises. The more economical way is to test the coating thickness of some expensive coating materials, and at the same time strengthen the test of the overall thickness of the film to effectively control the thickness uniformity of other layers of materials. Thickness measuring equipment can be divided into two categories: online thickness measuring equipment and offline thickness measuring equipment. For a detailed introduction of these two types of equipment, please refer to the article "Common Measurement Methods of Film Thickness". It would be more ideal if these two kinds of thickness measuring equipment can be used together. On the one hand, on-line thickness measuring equipment often adopts non-contact measuring method, which can't avoid large data fluctuation caused by poor compressibility or surface smoothness of soft packaging materials, while off-line thickness measuring equipment can provide contact measuring method (such as mechanical thickness measuring method adopted by Labthink CHY-C2), which effectively makes up for this deficiency of on-line thickness measuring. On the other hand, on-line thickness measurement can effectively control the thickness uniformity of a batch of films, but it is not suitable for sampling inspection of finished films, so off-line thickness measurement equipment must be equipped. On-line thickness measuring equipment can obtain thickness measuring data at the fastest speed, adjust production line parameters in time, reduce material thickness fluctuation and shorten production line start-up time. However, it needs to be equipped with a scanning frame matching the production line, which limits its repeated use, and the price, operation and maintenance costs of the equipment are much more expensive than those of off-line thickness measuring equipment. Off-line thickness measuring equipment is cheap, small and easy to use, but the feedback of thickness parameter adjustment of production line is much slower. There are many kinds of off-line thickness measuring equipment, among which mechanical thickness measuring technology is the most suitable. It is not selective to samples, and the test is not affected by the change of product color and composition or surface reflection. It can be used to detect any substance, while measuring the thickness, it will exert a certain pressure on the measured surface of the sample, which can effectively avoid the situation that the data fluctuates greatly due to the poor compressibility or surface flatness of the sample, and is very suitable for the thickness detection of soft packaging materials. In addition, due to the compressibility of the film, there is often a gap between the thicknesses of the same film detected by various thickness gauges. Therefore, it is very important to select instruments in strict accordance with the conditions stipulated in the standard. 3. It is expected that by increasing the test of material thickness uniformity, the rejection rate of packaging materials will be reduced and the cost will be saved. Due to the compressibility of flexible packaging material structure, mechanical thickness gauge has always been the first choice for thickness detection of various flexible packaging materials. However, the contact measurement of mechanical thickness measurement limits its development in the field of online thickness measurement. Therefore, in order to effectively control the thickness uniformity of materials, it is best to have both online and offline thickness detection equipment, which needs to be decided by enterprises according to the comprehensive factors such as material type, thickness uniformity control requirements, equipment budget and so on.