Moisture resistance of paper and paperboard

Raw paper and corrugated paper, especially corrugated paper, have significant water absorption. When the paper is exposed to a humid environment for a long period of time, its water content increases, which in turn leads to a significant reduction in the paper's transverse ring compression strength. At a relative humidity of 85%, the ring compression strength may even drop by 60%.

Corrugated cardboard boxes have poor water and moisture resistance, a defect that has been criticized by the market. As the cold chain packaging market for chilled meat, fruits and vegetables, and pharmaceuticals continues to expand, the corrugated packaging industry is in urgent need of a fundamental solution to the problem of carton packaging that is prone to collapsing after being exposed to moisture.

To this end, we have compiled the following top ten waterproof and moisture-proof solutions for corrugated cartons for the industry's reference:

Heavily sized containerboard

By adding a large number of water-resistant additives, such as urea-formaldehyde resins, melamine formaldehyde resins and polyvinyl butyral, etc., to the papermaking process of boxboard, the surface of boxboard can be heavily sized. This ensures to a certain extent that water droplets cannot penetrate the surface of the cardboard within 5 minutes. However, this method is relatively costly and may cause problems such as gluing during the production of corrugated board.

Paper water repellents

Paper water repellents are wax-containing water-resistant, hydrophobic agents with excellent dispersing properties that penetrate evenly into the pores of the paper product's fibers. This waterproofing agent resists penetration of other objects and forms a waterproof layer on the surface of paper products. The treated paper products not only significantly improve the water resistance, but also effectively improve the surface gloss and feel performance, so that the coating film is smoother.
Laminating paper

Laminating paper is a composite material formed by coating plastic particles on paper through a casting machine. It is oil- and water-resistant (relatively speaking) as well as heat-laminatable. However, the relatively high cost of laminated paper has limited its widespread use in the packaging industry.

Hydrophobic Corrugated Board

Hydrophobic corrugated board, also known as water-repellent corrugated board, has its surface properties altered by coating the surface of the board's face paper with low-surface-energy substances such as polylactic acid and polyolefins. These substances reduce the surface tension of the board, giving it a hydrophobicity similar to that of a lotus leaf. When a drop of water falls on the hydrophobic corrugated board, it forms a slippery droplet that does not penetrate into the interior of the board. This type of cardboard is ideal for packaging dry powdered items, especially those that tend to clump together when water is absorbed. It is also suitable for goods that are frequently in and out of cold storage, as dew in cold storage does not significantly reduce its compressive strength until it evaporates, thus effectively protecting the goods.