1. The function of moisture-proof packaging bag and the material of the packaged materialMoisture-proof packaging bags are very important for those products whose management will be affected after moisture absorption. The moisture-proof packaging bag can prevent the goods from being damaged by external moisture during storage and transportation. For example, medicines, crispy foods, close-fitting instruments, metal products, etc. will deteriorate in quality after being affected by moisture, and even lose their use value.Moisture-proof packaging bags are also very important for those products that have a lot of moisture in themselves, and the treatment will be affected after losing moisture. lose use value.From the perspective of moisture-proof packaging bags, the packaged objects can be roughly classified as follows:①Hygroscopicity: Low moisture content: Absorption of external moisture will affect the quality. Products such as medicines, cement, etc. can be prevented from absorbing moisture through moisture-proof packaging bags.High moisture content: The quality of the product will decrease when it loses water. Water loss can be avoided by moisture-proof packaging bags, such as bread, cosmetics, etc.②Non-hygroscopic: The product itself has no hygroscopicity, but in a high-humidity environment, it has an image on the quality of the product, and the product can be separated from the high-humidity environment by the moisture-proof packaging bag, such as metal.2. Hygroscopic articlesThere are many types of hygroscopic packaging materials. From the perspective of moisture-proof packaging bags, they can be divided into the following three types: 1, products with dilution isothermsAfter the product absorbs moisture from the air or evaporates moisture into the air, it increases or decreases the moisture content of the pigeons. The proportion of this change decreases with time, and finally reaches a state where it no longer absorbs or dehumidifies. As long as the temperature and humidity conditions in the air do not change, the moisture content of the product will not change. Therefore, under certain temperature and humidity conditions, when the moisture of the product is in balance with the moisture of the outside world, the moisture content of the product is certain. At this time, the moisture contained in the product is called balanced moisture. At a certain temperature, the higher the humidity of the air, the more the corresponding equilibrium moisture. When the relative humidity of the environment drops at a certain temperature and the equilibrium moisture of the product is plotted, the moisture absorption isotherm of the product can be obtained. Moisture absorption or dehumidification isotherms are important in moisture barrier packaging to prevent moisture absorption or dehumidification of the packaged product. 2, products with balanced humidityProducts with inorganic salts as the main components, such as chemical fertilizers and industrial medicines, each have a certain equilibrium humidity. Generally, the equilibrium humidity changes with the change of temperature, but the equilibrium humidity of table salt at room temperature hardly changes with the change of temperature. For packaged products with equilibrium humidity, when the external relative humidity is higher than the equilibrium humidity of the product, the product absorbs the moisture of the air, so that the air humidity of the packaging space tends to the equilibrium humidity of the product; when the relative humidity of the packaging space When the humidity is lower than the equilibrium humidity of the product, the product evaporates water into the air, so that the air humidity in the packaging space tends to the equilibrium humidity of the product. 3, liquid productsThe relative humidity inside the packaging container can be as high as90%-100%. Such products should be packaged in moisture-proof packaging to prevent the loss of moisture and affect product quality.3. Non-hygroscopic productsGlass, ceramics, metals, etc. are all non-hygroscopic. Such products themselves do not contain moisture or have no hygroscopicity, but some non-hygroscopic products also need moisture-proof packaging, especially metal products, which need moisture-proof for the purpose of rust prevention.