Adhesion of corrugated cardboard ink is a key indicator of print quality, and its performance is significantly affected by ambient temperature and humidity. During the corrugated cardboard printing process, fluctuations in temperature and humidity alter the interaction between the ink and the substrate through both physical and chemical pathways, thereby affecting adhesion stability. This process involves complex changes in the ink's rheological properties, the substrate's surface conditions, and the drying and curing efficiency.
Ambient humidity has a dual impact on the adhesion of corrugated cardboard ink. When humidity is too high, water molecules in the air penetrate the corrugated cardboard fibers, increasing the cardboard's moisture content. Cellulose absorbs water and expands, making the cardboard surface softer and reducing its tension. This physical change weakens the mechanical bond between the ink and the cardboard fibers. Furthermore, high humidity slows the evaporation of the ink's solvent, causing the ink layer to remain moist for extended periods. This can lead to uneven ink transfer or localized buildup, ultimately reducing adhesion. Conversely, under low humidity conditions, cardboard fibers shrink due to water loss, becoming brittle and increasing surface roughness. While this may initially enhance mechanical adhesion of the ink, overdrying can cause the ink layer to solidify rapidly, forming a brittle interface that can easily lead to adhesion failure during subsequent handling or stacking.
The impact of temperature on the adhesion of corrugated cardboard ink is primarily reflected in the regulation of ink viscosity and drying efficiency. Increasing ambient temperature reduces ink viscosity and enhances its fluidity, which helps the ink penetrate the cardboard's microporous structure and form a secure anchor point. However, if the temperature is too high, the binder in the ink decomposes due to thermal decomposition, reducing viscosity. Simultaneously, rapid solvent evaporation can cause a skinning on the surface of the ink layer, hindering the uniform escape of the solvent within, resulting in a "false dry" phenomenon and severely impairing adhesion. Furthermore, high temperatures accelerate the hydrolysis of the adhesive in the corrugated cardboard, reducing the cardboard's inherent adhesive strength and indirectly weakening the foundation for ink adhesion. At low temperatures, the ink's viscosity increases, its fluidity decreases, making it difficult to fully wet the cardboard surface, resulting in reduced adhesion.
The synergistic effects of temperature and humidity on the adhesion of corrugated cardboard ink are even more complex. In high-humidity and high-temperature environments, the conflict between cardboard moisture content and ink drying speed is particularly pronounced. Water molecules not only hinder solvent evaporation but can also participate in the cross-linking reaction of the ink's resins, altering the ink's curing mechanism and forming an unstable adhesion layer. Under low-humidity and high-temperature conditions, the increased brittleness of the cardboard fibers combined with the rapid curing of the ink can easily lead to cracking or shedding of the ink layer under stress. This synergistic effect is particularly pronounced in printing on multi-layer corrugated cardboard, where varying moisture content in different layers can cause localized uneven adhesion.
Printing companies need to implement systematic measures to control ambient temperature and humidity. For humidity control, dehumidifiers or humidifiers can be installed to maintain a suitable relative humidity in the workshop to prevent excessive moisture absorption or dehydration. Temperature control requires a combination of air conditioning systems and localized heating to ensure stable rheological properties of the ink during the printing process. Furthermore, it is crucial to select an ink system that matches the temperature and humidity conditions, such as using fast-drying inks in high-humidity environments and low-viscosity resin formulations in low-temperature conditions.
The stability of corrugated cardboard ink adhesion depends on precise control of ambient temperature and humidity. By understanding the mechanisms by which temperature and humidity influence ink rheology, the physical state of the cardboard, and the drying process, printers can optimize process parameters and select appropriate ink products, thereby achieving high-quality printing results under complex environmental conditions. This process requires not only advanced equipment but also a scientific temperature and humidity management system to lay the foundation for the continued improvement of corrugated cardboard ink adhesion.
