The abrasion resistance of woven bag ink is a key indicator of print quality and durability, directly impacting the clarity and appearance of information during transportation, storage, and use. Abrasion resistance is influenced by multiple factors, including ink formulation, substrate properties, curing process, environmental conditions, and additive selection. It requires a comprehensive consideration of chemical structure, physical properties, and process control.
The resin type in the woven bag ink formulation is a fundamental factor in determining abrasion resistance. The molecular crosslink density of different resins varies significantly. For example, epoxy resin, due to its dense crosslinking structure, generally exhibits better abrasion resistance than acrylic resin. The resin's glass transition temperature (Tg) also influences the coating's flexibility. While high-Tg resins offer increased hardness, they also increase brittleness, potentially reducing friction resistance. Low-Tg resins, while flexible, are susceptible to coating wear due to excessive deformation. Therefore, the resin type should be selected based on the characteristics of the woven bag material. For example, modified acrylic resins with strong adhesion and flexibility are preferred for polypropylene woven bags.
The influence of substrate properties on the abrasion resistance of woven bag ink cannot be ignored. The surface roughness, porosity, and chemical composition of woven bags directly affect ink penetration and adhesion. Untreated woven bags can have interfiber gaps that lead to uneven ink penetration and a weak interface. Corona or plasma treatments can increase surface energy, improve ink wettability, and thus enhance the mechanical bond between the coating and the substrate. Furthermore, the substrate's water absorption is a key consideration. Highly absorbent materials can cause the coating to swell and detach due to water penetration, reducing wear resistance.
The curing process is crucial for controlling wear resistance. The degree of ink curing directly affects the crosslinking density of the coating. Incompletely cured coatings, due to insufficient molecular chain connection, are susceptible to detachment due to friction. For UV-curable inks, sufficient UV energy and exposure time must be ensured to avoid a decrease in wear resistance due to insufficient curing. For oxidatively drying inks, controlled drying temperature and ventilation are essential to prevent residual solvents from weakening the coating's hardness. Experimental results show that fully cured UV inks can withstand more than six times the number of abrasions as uncured samples.
The appropriate use of additives can significantly improve wear resistance. Wear-resistant additives such as nanosilica and polytetrafluoroethylene wax powder reduce the coefficient of friction and improve wear resistance by forming a lubricating layer on the coating surface or strengthening the cross-linking structure. Adhesion promoters improve the interfacial bonding between the woven bag ink and the substrate, reducing coating delamination caused by stress concentration. Furthermore, leveling agents eliminate surface defects in the coating, preventing uneven surfaces from exacerbating friction damage. However, care must be taken with the dosage of these additives; excessive addition may cause coating embrittlement or a reduction in gloss.
Ambient temperature and humidity influence wear resistance throughout the printing process. High temperatures and high humidity accelerate solvent volatilization in the ink, leading to uneven coating shrinkage and internal stress. Low temperatures and low humidity can prolong drying time and increase the risk of coating contamination or mechanical damage. In humid weather, woven bags easily absorb moisture and expand, resulting in uneven pressure distribution during ink transfer, causing blurred prints or de-inking. Therefore, printing should be performed in a constant temperature and humidity workshop, and the temperature and humidity of the ink storage and use environment must be strictly controlled.
Optimizing printing process parameters is crucial for improving wear resistance. Too little printing pressure can lead to insufficient ink transfer and uneven coating thickness; excessive pressure can crush the woven bag fibers and damage the substrate structure. The squeegee angle and hardness must be adjusted according to the ink viscosity to avoid a rough coating surface caused by incomplete scraping. Furthermore, the printing speed must match the ink drying speed to prevent adhesion or smearing caused by insufficient drying.
The abrasion resistance of woven bag ink is a result of a combination of formulation design, substrate preparation, curing process, additive selection, and environmental control. By optimizing the resin type, increasing the substrate surface energy, ensuring complete curing, appropriately adding anti-wear additives, and strictly controlling the printing environment, the ink's abrasion resistance can be significantly improved, thus meeting the quality requirements of woven bags in complex usage scenarios.
