Packaging leaks and leaks

Leakage of packaging generally has two types: one is the inevitable leakage due to the design and structure itself, this leakage can be solved by changing the design and structure of the packaging; the other is due to the packaging in the manufacturing, Leakage caused by defects in the course of transportation, etc. This leakage can be resolved through adjustments without changing the design and structure. Determining if there is a leak in a package and determining the location of the leak is important for the packaging project. At present, the commonly used packaging leak testing methods at home and abroad are shown in Table 1.

From the point of view of the test method, the leakage of the packaging is generally qualitative. The purpose of the inspection is mainly to detect whether there is a certain package in the production of packaging materials, molding, filling, heat sealing, sterilization, and storage, transportation and sales. Some defects cause product leakage.

There are generally two types of leaks caused by defects in products: press-through and leak-sealing. Press-through refers to the packaging material being pressed by an external force to form a penetrating hole or crack. The reasons for this are generally: 1 The heat seal pressure is too high. In the process of heat sealing, if the heat sealing pressure or the heat sealing mold is not parallel, the local pressure is too large, and some relatively fragile packaging materials are often pressed through. 2 heat sealing mold rough, angular or foreign body. Poorly manufactured heat-sealing molds often crush the packaging materials. Some heat-sealing molds will produce sharp edges after impact, and they can easily press through the packaging material. 3 The thickness of the packaging material was not selected correctly. Some packaging machines require thickness of the packaging material. If the thickness is too large, some locations of the packaging bag may be pressed through. For pillow type packaging machines, the thickness of the packaging material should not exceed 60 μM. If the packaging material is too thick, it can be easily broken in the sealing area of ​​the pillow type packaging. 4 Wrong choice of packaging material structure. Some packaging materials have poor compression resistance and cannot be used to package some hard, angular materials. For example, a paper-aluminum-plastic composite material is used to package granular granules. 5 Improperly designed packaging mold. In the design process, if the die hole of the heat seal film does not conform to the shape and size of the packaged material, and the mechanical strength of the packaging material is different, it is easy to press through or fracturing the packaging material during the packaging process.

Leakage sealing is due to the presence of certain factors, so that the part that should have been bonded by heating and melting is not sealed. Leakage seals generally have the following reasons: 1 The heat seal temperature is not enough. The same sealing materials require different heat sealing temperatures in different heat sealing locations, different packaging speeds require different heat sealing temperatures, different packaging temperatures require different heat sealing temperatures, and the sealing and sealing requirements of the packaging equipment are the same as the sealing temperatures. Differently, in the same heat-sealing mold, the temperatures of different parts may not be the same. These are problems that must be considered in the packaging. For the heat sealing equipment, there is also a problem of temperature control accuracy. At present, domestic packaging equipment has poor temperature control accuracy, and generally has a deviation of ±10°C. That is, if the temperature that we control is 140°C, the actual The temperature during the packaging is between 130°C and 150°C. Many companies' airtightness inspections use random sampling in finished products to check. In fact, this is not a good method. The most reliable method is to sample at the lowest temperature point in the temperature range, and it should be sampled continuously so that the sample can cover all parts of the mold longitudinally and longitudinally. 2 The sealing area is contaminated. In the filling process of the packaging, the sealing position of the packaging material is often contaminated by the packaging material, and the pollution is generally divided into liquid pollution and dust pollution. The problem of contaminating the sealing area can be solved by improving the packaging equipment and using anti-pollution and anti-static heat sealing materials. 3 equipment and operation problems. If the heat seal film has foreign matter, the heat seal pressure is not enough, and the heat seal film is not parallel. 4 Problems with packaging materials. If the corona is too thick, too many heat-sealant slip agents cause poor heat sealing.

There is also a “half leak” in the actual leakage of packaging, which means that in the process of molding, filling, heat-sealing, sterilizing, and transporting and selling of packaging products, although there is no perforation leakage between the inside and outside, but its high barrier Layers (such as aluminum foil, SIOX barrier coating or plating) produce cracks or pinholes, and "semi-leakage" will seriously affect the overall sealing performance of the package, which is a non-negligible factor in the packaging process. I have done some research work on the pinholes of aluminum foil and its influence on barrier properties, and obtained the theoretical formula for calculating oxygen permeability and water vapor transmission rate of aluminum foil and its composite materials from pinhole parameters of aluminum foil. How to reduce the cracks and pinholes of the barrier layer in the process of packaging and distribution of packaging materials in the aspects of packaging design, material selection, packaging equipment, etc.; how to detect the crack resistance of packaging materials; how to evaluate barrier layer folding The impact of cracking on packages is a very significant issue in practice. (From "Plastic Packaging," No. 1, 2002)