Viscosity of inks with different compositions

Date: Jan 29 2025 From: Star Color

Printing Ink, as a core consumable in the printing industry, directly influences the quality of printed materials. Among the numerous performance indicators of ink, viscosity plays a pivotal role. Inks of different compositions exhibit varying viscosities due to differences in their chemical structures and physical properties. Next, let's explore the mysteries of viscosity within the classification of ink components.

Solvent-Based Ink: The "Chameleon" with Diverse Viscosity

Solvent-based ink primarily uses organic solvents to dissolve resins, pigments, and other components. Its viscosity range is relatively broad, typically between 50 - 5000mPa·s. This is because solvent-based inks have different viscosity requirements across various printing processes and application scenarios.

In gravure printing, solvent-based inks need to have a lower viscosity, usually within 50 - 500mPa·s, to ensure the ink can quickly and evenly fill the engraved pits on the printing cylinder and smoothly transfer to the substrate surface, such as for printing packaging materials like plastic films and metal foils. In some special screen printing applications, the viscosity of solvent-based inks may increase to 1000 - 5000mPa·s to meet the needs of specific patterns and printing effects.

The adjustable viscosity of solvent-based inks benefits from the volatile properties of organic solvents. By adjusting the type and proportion of solvents, the viscosity of the ink can be flexibly changed. However, the volatilization of organic solvents also poses issues of environmental pollution and safety hazards.

Water-Based Ink: The "Environmental Pioneer" with Low Viscosity

Water-based ink uses water as the main solvent, offering environmental friendliness, non-toxicity, and no irritating odor. Its viscosity generally ranges between 200 - 2000mPa·s, relatively low.

The low viscosity of water-based inks is partly determined by the physical properties of water. Water's lower surface tension makes water-based inks easier to flow and spread during the printing process. Additionally, to ensure good transfer performance of water-based inks on printing equipment, their formulation design also tends to maintain a lower viscosity.

In flexographic printing and inkjet printing, the low viscosity advantage of water-based inks is fully leveraged. In flexographic printing, water-based inks can be evenly transferred from the anilox roller to the flexible plate and then to the substrate surface, achieving clear and exquisite printing effects, commonly used for printing labels, corrugated cartons, etc. In inkjet printing, low-viscosity water-based inks can smoothly pass through the printhead, forming fine ink droplets to meet the printing needs of high-precision images and text.

Oil-Based Ink: The "Traditional Guardian" with High Viscosity

Oil-based ink uses oils as the main binder, such as linseed oil and tung oil. Its viscosity is relatively high, typically ranging between 10000 - 50000mPa·s.

The high viscosity of oil-based inks mainly stems from the characteristics of oils. Oils have higher molecular weights and viscosities, making oil-based inks thicker at room temperature. High-viscosity oil-based inks can better maintain their shape and stability during the printing process, resisting flow and diffusion.

In some printing applications requiring special textures and artistic effects, such as artistic painting and special binding printing, the high viscosity of oil-based inks can form thick, layered ink films, exhibiting unique artistic charm. Additionally, the dried ink film of oil-based inks has good flexibility and gloss, which is also one of the reasons they are still widely used in specific printing fields.
Viscosity of inks with different compositions

UV Ink: The "Technological Favorite" with Adjustable Viscosity

UV ink is primarily composed of oligomers, monomers, photoinitiators, pigments, and additives. Its viscosity range can be adjusted according to specific printing processes and requirements, typically between 500 - 50000mPa·s.

In UV offset printing, to ensure good transfer and performance of the ink between ink rollers, the viscosity of UV ink is usually controlled between 10000 - 30000mPa·s, similar to the viscosity range of traditional offset printing inks. In UV screen printing, to meet the requirements of fluidity and filling performance of screen printing inks, the viscosity of UV inks may be reduced to 500 - 5000mPa·s.

The adjustable viscosity of UV inks benefits from their special curing mechanism. Under ultraviolet light, the photoinitiators in UV inks absorb light energy to generate radicals or cations, initiating polymerization reactions between monomers and oligomers, thereby rapidly curing the ink. By adjusting the types and proportions of oligomers, monomers, and additives, the viscosity of UV inks can be effectively controlled to adapt to different printing methods and substrate materials.

The composition of ink is closely related to its viscosity, with inks of different compositions exhibiting unique viscosity characteristics during the printing process. Understanding these characteristics not only helps printing professionals select suitable inks according to different printing needs but also better controls printing quality to create more exquisite printed materials. With continuous technological advancements and increasing environmental protection requirements, the composition and performance of inks are constantly being innovated and optimized, and the mysteries of ink viscosity will continue to be rewritten and enriched in the future.