The temperature and humidity of Kraft paper bags' storage environment are key factors affecting their long-term preservation quality. Fluctuations in temperature and humidity can directly alter the paper's physical structure and chemical stability, thereby affecting its load-bearing capacity, printing quality, and lifespan. During storage management, precise temperature and humidity control is essential to prevent irreversible damage to Kraft paper bags caused by extreme environments.
The impact of temperature on Kraft paper bags is primarily reflected in fiber thermal motion and water evaporation rates. When storage temperatures exceed 25°C, thermal motion within the paper's internal fibers intensifies, weakening interfiber bonds and making the paper brittle and prone to breakage. High temperatures, especially for thick Kraft paper bags, accelerate internal water evaporation, causing cracks at creases when folded or loaded, and weakening its structural strength. Conversely, if the temperature is below 15°C, water vapor in the air tends to condense on the paper's surface, forming condensation. Condensation can cause a sudden increase in the paper's moisture content in certain areas, leading to uneven fiber expansion, deformation, wrinkling, and, in severe cases, even mold growth.
Humidity has an even more significant impact on the storage quality of Kraft paper bags. Kraft paper bags are highly hygroscopic. When the storage humidity exceeds 65%, the paper absorbs a large amount of moisture from the air, causing the fibers to swell and the structure to loosen. This significantly reduces the tensile strength of the Kraft paper bags. For example, after one month of storage in a humid environment, the tensile strength may drop by 10%-15%. The bags are also prone to deformation and mold. Mold in humid environments decomposes the cellulose and lignin in the paper, destroying the fiber structure, causing discoloration and rotting, rendering the paper useless. When the humidity falls below 45%, excessive moisture loss from the paper causes the fibers to dry out and become brittle, reducing the paper's flexibility and impact resistance, and making it susceptible to cracking during handling or use.
To maintain stable temperature and humidity in the storage environment, professional environmental control equipment is required. Air conditioning systems can regulate the temperature to maintain a suitable storage environment within the range of 15-25°C, preventing damage to the Kraft paper bags caused by high or low temperatures. Dehumidifiers and humidifiers can work together to maintain a humidity level between 45% and 65%. During humid seasons, dehumidifiers can reduce air humidity and prevent paper from absorbing moisture. During dry seasons, humidifiers can replenish air moisture to prevent paper from losing moisture and becoming brittle. Furthermore, storage facilities should be equipped with temperature and humidity sensors to monitor environmental data in real time. A coordinated system automatically adjusts equipment operation to ensure that temperature and humidity remain within controllable limits.
The stacking method of Kraft paper bags also affects their sensitivity to temperature and humidity. Stacking heights should generally not exceed 1.5 meters. The bottom layer of paper should be placed on pallets, avoiding direct contact with the ground to prevent moisture from penetrating and causing moisture to the bottom layer. Furthermore, when stacking, ensure that the paper is flat and avoid tilting to prevent it from slipping or curling. Kraft paper bags of different sizes and batches should be stored separately. Frequently used sizes should be placed on shelves near the door for quick access and to minimize damage to the paper from frequent handling.
Regular inspection and maintenance are crucial to ensuring the long-term quality of Kraft paper bags. Check the paper quality at least weekly to observe for mold, discoloration, or damage, and address any issues promptly. For long-term storage (over 6 months), paper should be turned regularly to prevent deformation of the bottom sheet due to prolonged pressure. This ensures that the paper is evenly exposed to air to maintain moisture balance. Furthermore, the storage area should be kept clean, with dust and debris regularly removed. Door and window gaps should be sealed to prevent entry by rats and insects. Insect and rodent repellents may be used if necessary, but direct contact between the repellent and the paper should be avoided to prevent contamination.
