The Adhesion of UV Flexo Ink on Non-Porous Surfaces

Date: Jun 24 2025 From: Star Color Views:

UV flexographic inks have become the preferred material for many printing enterprises due to their unique advantages. They can cure rapidly in a short time, significantly improving production efficiency. Meanwhile, they can present high-quality printing effects with vivid colors and clear layers, meeting the market demand for exquisite packaging and labels.

When printing on non-porous surfaces, the adhesion of many inks often becomes an issue. Will UV inks suffer from insufficient adhesion, leading to color fading? Let’s elaborate on this below.

What are Non-porous Surfaces?

Non-porous surfaces are fundamentally different from absorbent substrates like paper and cardboard. Their surface structure is dense, unable to absorb inks like the latter, so the ink can only adhere to the material's surface.
Common non-porous substrates include:

PVC, PE, PP films
PET, BOPP, and composite film materials
Synthetic paper (synthetic substrates)
Aluminum foil and metallized materials

These materials are widely used in flexible packaging, heat-shrinkable films, labels, and industrial product identification, featuring good moisture resistance and durability.

zhongzhixing UV flexo ink

Why Does Adhesion Often Fail?

Non-porous substrates have smooth surfaces like mirrors, making it difficult for inks to adsorb. Such materials typically have low surface energy or inert chemical properties. Excessively low surface energy prevents the ink from fully wetting the substrate surface, resulting in weak intermolecular forces between the two and difficult firm bonding. The surface energy of untreated PE film is only about 31–34 dyn/cm, far lower than the wetting surface energy required by most UV flexographic inks.

During the production, storage, and transportation of materials, the surface is highly prone to contamination. Pollutants such as dust, oil, and antistatic agents adhering to the substrate surface form a barrier between the ink and the substrate, hindering their direct contact and bonding. Statistics show that ink adhesion issues caused by surface contamination account for more than 30% of actual production problems.

Extremely low substrate surface energy
Surface contamination (e.g., dust, oil, antistatic agents)
Lack of surface treatment (e.g., corona treatment or plasma treatment)
Inappropriate ink formulation or UV curing parameters

Core Principles of UV Flexographic Ink Adhesion

The matching degree between the substrate's surface energy and the ink's surface tension directly determines the ink's wetting effect on the substrate surface. When the substrate's surface energy is higher than the ink's surface tension, the ink can fully spread on the substrate surface, forming a uniform ink film and closely contacting the substrate's surface molecules, laying the foundation for subsequent bonding. Take corona treatment as an example: the surface energy of PET film after corona treatment can be increased from about 42 dyn/cm to 48–52 dyn/cm, significantly improving its wettability with UV flexographic inks.

According to the characteristics of non-porous surfaces, R&D personnel need to carefully design UV ink formulations. Reasonably selecting monomer combinations can adjust the ink's viscosity, drying speed, and curing performance; adding adhesion promoters can enhance the chemical bonding or physical adsorption between the ink and the substrate.

During R&D, StarColor has developed exclusive ink formulations for different types of non-porous surfaces through extensive experiments and tests to meet the market demand for high-adhesion inks.

In the UV curing process, the ultraviolet energy emitted by the UV lamp promotes the decomposition of photoinitiators in the ink to generate free radicals, thereby triggering cross-linking reactions between monomers and prepolymers to form a three-dimensional network film. Excessively fast curing or insufficient curing will affect the ink's adhesion performance. Precisely controlling the UV lamp power, irradiation time, and ink curing speed to ensure sufficient ink cross-linking is the key to improving ink adhesion and printing quality.

Tips to Improve UV Ink Adhesion

Test the substrate surface tension (recommended to be >38 dyn/cm)
Use surface-treated materials (e.g., corona treatment, flame treatment)
Choose ink formulations specially designed for non-porous surfaces
Ensure sufficient UV lamp power for complete curing
Avoid substrate surface contamination by oil or silicone before printing

StarColor’s Professional Solutions

With years of deep involvement in the UV flexographic ink field, StarColor has developed a series of high-adhesion UV flexographic ink products for the printing needs of non-porous surfaces. These products are suitable for various non-porous materials such as PE, PET, PVC, and aluminum foil, enabling good adhesion on different substrate surfaces. After curing, the ink film exhibits excellent alcohol resistance, water resistance, and scratch resistance, maintaining the integrity and clarity of printed patterns even in harsh environmental conditions.

In terms of printing performance, StarColor’s inks have high fluidity, enabling precise dot transfer in flexographic printing to restore delicate and clear printed patterns, meeting the quality requirements of high-end packaging and label printing.
Meanwhile, StarColor always upholds the concept of environmental protection. Its ink products are free of heavy metals and comply with international regulations such as RoHS, REACH, and FDA, providing customers with safe and reliable printing solutions.

Additionally, StarColor offers personalized ink customization services. According to customers’ special printing needs, such as specific color requirements or targeted chemical resistance, the R&D team will conduct targeted formula adjustment and optimization.

When printing on non-porous surfaces, through reasonable surface treatment, professional ink selection, and precise UV curing control, UV flexographic inks can also achieve excellent adhesion and durability on materials like plastic films and metal films. StarColor looks forward to being your stable partner in high-difficulty substrate printing.