How does corrugated cardboard ink maintain adhesion in humid environments?
Publish Time: 2025-08-28
In the modern packaging industry, corrugated cardboard is widely used in logistics and product packaging due to its lightweight, environmentally friendly, low-cost, and excellent cushioning properties. However, corrugated cardboard often faces challenges in practical use, particularly during rainy seasons, during sea transportation, or in high-humidity storage conditions. Moisture absorption can easily lead to decreased adhesion of corrugated cardboard ink, resulting in ink bleeding, discoloration, and blurring, seriously impacting product appearance and brand reputation.
1. The Mechanism of Humidity's Impact on Ink Adhesion
Corrugated cardboard is primarily composed of base paper, which is highly absorbent. When humidity rises, the cardboard fibers absorb water and expand, reducing surface tension and altering the pore structure, making it difficult for ink to effectively penetrate and anchor. Furthermore, the presence of moisture weakens the chemical bonding and physical adsorption between the ink and paper fibers, making the ink layer more susceptible to peeling from the paper surface. Furthermore, water-based inks inherently contain a large amount of water, which slows drying in high-humidity environments, making incompletely cured ink more susceptible to external rubbing. Therefore, the key to improving ink adhesion in humid environments lies in enhancing the ink's ability to bond to the wet paper surface and accelerating the drying and curing process to prevent moisture interference.
2. Optimizing Ink Formulations: Shifting from "Hydrophilic" to "Wet-Resistant"
Modern corrugated cardboard printing widely uses water-based inks for their environmental friendliness, non-toxicity, and low cost. However, traditional water-based inks perform poorly in humid environments. To address this, ink manufacturers are using various technologies to improve their moisture resistance:
Introducing Crosslinkers: Adding crosslinkers (such as aziridines and isocyanates) to the ink creates a three-dimensional network structure during the drying process, enhancing the ink film's density and water resistance. Even if the cardboard becomes damp, the ink layer is less likely to dissolve or peel.
Modifying Resin Systems: Using highly water-resistant acrylic resins or polyurethane emulsions as film-forming agents improves the ink film's resistance to penetration and reduces moisture erosion.
Additives: Wetting and dispersing agents, defoamers, and anti-settling agents are added to improve the spreadability and stability of the ink on damp paper. Tackifying resins are also used to enhance the adhesion of the ink to the fiber.
Through these formulation optimizations, modern high-performance water-based inks maintain excellent adhesion even in environments with relative humidity exceeding 80%.
3. Cardboard Pretreatment: Improving the Substrate's "Wet Resistance"
In addition to the ink itself, the surface condition of the cardboard is also crucial. Some advanced corrugated cardboard manufacturers pre-treat the cardboard before printing:
Surface Sizing: Sizing agents (such as ASA and AKD) are added during the base paper production process to improve the paper's water resistance and reduce hygroscopic expansion.
Plasma or Corona Treatment: Physically increasing the cardboard's surface energy improves ink wettability and adhesion, and is particularly suitable for high-gloss or low-surface-energy paperboard.
Pre-Drying: Moderately drying the cardboard before printing reduces its initial moisture content, creating favorable conditions for rapid ink drying.
These treatments can effectively improve the printability of cardboard in humid environments, providing a more stable foundation for ink adhesion.
4. Coordinated Control of Printing and Drying Processes
Even with high-performance inks and high-quality cardboard, improperly controlled printing processes can still lead to adhesion issues. The key lies in:
Precisely controlling printing pressure and anilox roller line count to ensure even ink transfer and avoid excessive buildup that can lead to poor drying.
Using high-efficiency drying systems, such as hot air drying, infrared drying, or LED-UV assisted curing, accelerates water evaporation from the ink, shortens drying time, and prevents wet ink from being rubbed off during subsequent handling.
A staged drying strategy: Initially drying slowly at low temperatures to prevent surface filming, followed by rapid drying at high temperatures for complete curing, thereby improving the crosslinking density and adhesion of the ink film.
Maintaining adhesion of corrugated cardboard ink in humid environments is a systematic process that relies on a multi-dimensional synergy of ink formulation innovation, cardboard pretreatment, printing process optimization, and drying technology upgrades. As environmental protection requirements become stricter and the logistics environment becomes more complicated, the development of new inks that are more moisture-resistant, fast-curing, and green and environmentally friendly will become an important direction for the future development of corrugated cardboard printing technology.
