How to Increase the Hardness of Cardboard Boxes

In many industries, cardboard boxes are essential for packaging, but if their hardness is insufficient, the items stored in them can easily become deformed or damaged. Here are several ways to enhance the hardness of cardboard boxes:

1. Additives One method to increase the strength of corrugated boxes is by adding various chemical agents before or after the papermaking process. These additives improve the bonding strength of the materials, thereby boosting the compression resistance of the boxes. Common additives include corn starch, adhesives, glues, heavy metals, plastics, and urea-formaldehyde resins. In some cases, chemicals are sprayed onto the outer layer of the boxes to further reinforce the cardboard.
2. High Pressure High-pressure forming is another method to enhance the strength of cardboard during the papermaking process. This involves increasing the pressure points on the paper to compress the cardboard more tightly. The denser the cardboard structure, the greater its strength. This method also helps to extract more moisture from the pulp, but the key benefit is producing a stronger, more tightly compressed board with increased compression resistance.
3. Cross-Linking Cross-linking is a technique that changes the orientation of the fibers during the papermaking process. Typically, the fibers run parallel in a single direction, which weakens the box’s resistance to pressure when stacked horizontally. Cross-linking changes the fiber direction, placing many fibers at a 90-degree angle to the machine’s flow, resulting in fibers that run vertically on the edges of the box. This enhances the stacking strength of the box without increasing its weight.
4. Lamination This method involves reinforcing the strength of corrugated boxes by using two or more layers of paper. The core paper is laminated with adhesives, such as simple corn starch glue, to create a stronger core layer. This core is then sandwiched between cross-linked or conventionally pressed layers, boosting the overall strength of the box.

By applying these methods, the hardness and strength of cardboard boxes can be significantly improved, ensuring better protection for the products they hold.