Wetting agent: How does the "invisible assistant" of water-based ink make printing more perfect?Water-based ink is gradually becoming the "new favorite" of the printing industry because of its high environmental
protection and strong safety. However, the high surface tension of water as a solvent is like an invisible barrier, hindering
the close contact between ink and substrate. At this time, the wetting agent becomes an "invisible assistant" and uses
its unique "magic" to solve this problem.
1. Why does water-based ink need a wetting agent?
Water-based ink uses water as a medium, but the surface tension of water (about 72 mN/m) is much higher than that of
most substrates (such as paper about 35 mN/m, plastic is lower). This tension difference will make it difficult for the ink to
spread, and there will be problems such as "shrinkage holes", "fish eyes" or poor adhesion. The core function of the wetting
agent is to reduce the surface tension of the ink, making it easier to spread on the surface of the substrate, forming a uniform
and smooth printing effect.
2. The "magic" principle of the wetting agent
The wetting agent molecule has an "amphiphilic" structure: one end is hydrophilic and the other end is oleophilic. They will be
arranged in a directional manner at the interface between the ink and the substrate, connecting the two like a "bridge".
Reduce surface tension: reduce the tendency of droplet shrinkage by adsorbing on the surface of the ink.
Improve leveling: allow the ink to flow fully before drying and fill the pores of the substrate.
Enhance adhesion: promote the interaction between the ink and substrate molecules.
3. "Family members" of wetting agents
Anionic type (such as carboxylates):
High efficiency, but excessive amounts are prone to foaming and need to be used with defoamers.
Nonionic type (such as polyethers):
Good stability, strong compatibility, suitable for complex formula systems.
Fluorocarbon type:
Extremely strong wetting performance, but high cost, mostly used in high-end printing.
Silicone type:
Can reduce surface tension and improve leveling at the same time, but may affect the recoatability of the ink.
4. "Balance" in practical applications
Accurate control of the amount of addition:
Generally, the amount of addition is 0.5%~3%. Too little will not work, and too much will cause the ink to dry slowly and reduce
water resistance.
"Adaptation" of substrates:
Paper printing needs to focus on permeability, while plastic printing needs to focus on adhesion.
Synergy with other additives:
Often used in combination with dispersants and defoamers to avoid "loss of one for the other".
5. New challenges under environmental protection trends
Traditional wetting agents (such as APEO-containing ones) are gradually being eliminated due to poor biodegradability. The new
generation of wetting agents must meet the following requirements:
Degradability: Based on natural alcohols, bio-based polyethers and other raw materials.
Versatility: It has multiple effects such as wetting, leveling, and anti-slip.
Compliance certification: It complies with environmental protection standards such as REACH and GB/T.
6.. The future: Smart wetting agents are on the scene
With the development of nanotechnology, wetting agents are becoming "intelligent":
Stimulus-responsive: Automatically adjust surface tension through changes in temperature and pH value.
Targeted wetting agents: Molecular structures are designed for specific substrates (such as metals and textiles).
Carbon-based materials: Graphene derivatives may bring super wetting properties.
Conclusion
Although wetting agents are only a "supporting role" in the formulation of water-based inks, they are the key to improving
printing quality. In the future, with the improvement of environmental protection requirements and technological innovation,
wetting agents will evolve in a more efficient and intelligent direction, helping water-based inks to lead the way in the green printing race.
