Why does paper get warped? | 5 Reasons

Paper products generally have strong hygroscopic properties. When the weather is dry, the paper is easy to lose moisture, causing problems such as paper deformation, cracking, and shrinkage. Here, we will talk about the reasons for paper warping, tips for storage of kraft cardboard, and the solution to the warping of kraft paper.

5 Reasons for Paper Warping

The paper is mainly composed of lignocellulose. But cellulose is a substance with strong water absorption. It not only has strong water absorption but also strong dehydration. The changes in humidity and temperature during the printing process or storage will cause changes in the moisture content of the paper, resulting in shrinkage or expansion of the fibers in the paper.

The reasons for paper warping and deformation are as follows:

  1. The two sides of the paper have different moisture content. It causes the paper to bend to the side with more moisture;
  2. The temperature and humidity in the production, processing, packaging, and transportation environment are different. So the paper is bent and deformed;
  3. The deformation of kraft cardboard is usually that the part close to the core of the paper tube is more curved, especially the bending angle of kraft cardboard will be larger. The paper needs to be humidified to increase the moisture content of the paper. And at the same time, the paper should be flattened for a certain period of time.
  4. The unbalanced force on the two sides of the paper and the uneven shrinkage of the paper itself cause the paper to be warped and uneven.
  5. The loss and imbalance of moisture are one of the main factors causing paper deformation. So the paper must be packed in moisture-proof packaging during storage. Effective packaging can reduce the deformation of paper in the subsequent printing process. Thereby improving production efficiency, and reducing the generation of defective products.
rolls of paper corrugated raw paper

So what is the solution to the warping of kraft paper jam?

It is to adjust the humidity of the kraft cardboard. Then put it in an air-conditioned room to adjust the temperature and keep it at room temperature.

  • If the kraft paper card is warped due to loss of water, place the paper in a high-humidity environment and pay attention to time control.
  • If the kraft cardboard is caused by water absorption, put the paper at a high temperature and store it in a low-humidity environment.

During the storage process of kraft cardboard, we must pay attention to the temperature and humidity of the storage environment. In addition, kraft cardboard paper in general printing factories must adapt to the environment before printing. That is, put the cut paper under the same temperature and humidity as the printing environment. Leave it for a while.

What problems should be paid attention to in the preservation of kraft cardboard?

  1. When placed, it must be clean, dry, and well-ventilated. The kraft cardboard warehouse should be kept dry;
  2. Then there is protection against sunlight exposure. When the temperature rises in direct sunlight, a large amount of water will evaporate. The white kraft cardboard will become brittle, yellow, easy to crack, and fade;
  3. It is not allowed to pile up other chemicals or commodities with high water and oil content to be stored together;
  4. Especially during the rainy season in summer, you should pay more attention to moisture protection. The positions for stacking all kinds of kraft cardboard should be basically fixed. And it is necessary to observe and take protective measures in time so that the kraft cardboard will be as good as before without problems.

That’s all. I hope that you know now how to prevent the warping of paper rolls. If you have other questions, please leave your messages, and we will talk about them in the next blog.