Scratch resistance is a key performance requirement for UV-curable coatings used on plastics, glass, wood, PVC/SPC flooring, 3C electronics, automotive interiors, and other frequently handled surfaces. However, a scratch-resistant UV coating is not created by simply selecting a resin described as “high hardness” or “anti-scratch.”
The final result depends on the interaction between UV resin chemistry, cross-link density, formulation design, curing conditions, film properties, and substrate characteristics. For formulators, understanding these relationships is essential when developing coatings that need both surface durability and practical flexibility.
What Determines Scratch Resistance in a UV Coating?
UV resin is a major film-forming component in a UV-curable formulation. Its functionality, chemical structure, viscosity, hardness, flexibility, adhesion, and curing response can strongly influence the final coating.
1. Resin Functionality and Cross-Link Density
Functionality is one of the factors that affects the cross-linked structure formed during UV curing. Higher-functionality oligomers can generate denser networks, which may contribute to higher hardness and resistance to surface marking.
However, higher functionality does not automatically mean better overall performance. Excessive cross-link density can reduce flexibility or increase brittleness. The appropriate resin therefore depends on the required balance between hardness, toughness, adhesion, and flexibility.
The Lencolo UV resin portfolio includes grades ranging from difunctional products to resins with functionality up to 15, providing different options for formulation development.
2. Hardness Must Be Balanced With Flexibility
A very hard coating may resist certain scratching or abrasion tests but can become vulnerable to cracking when the substrate bends or experiences impact. Conversely, a highly flexible film may tolerate deformation but show lower surface hardness.
The required balance changes with the substrate. Glass and rigid plastic components may require a different resin design from leather, soft-touch plastics, or flexible films.
3. Curing Method and Cure Completeness
Mercury UV, UV LED, Excimer, and Dual Cure systems can produce different curing profiles and surface properties. The selected resin should therefore be compatible with the actual curing equipment and photoinitiator system.
Incomplete or uneven curing can reduce surface hardness and leave the film more susceptible to scratching. For this reason, scratch resistance should be evaluated together with curing speed, cure depth, surface dryness, and the actual UV energy used in production.
UV Resins for Scratch-Resistant Applications
Several Lencolo UV resin grades have documented scratch, wear, or abrasion-related characteristics. These products should be regarded as candidates for formulation testing rather than universal solutions.
Polyurethane Acrylates
L-6207 combines wear resistance and flexibility with fast curing and RCA resistance of more than 200 times. It is used in applications including 3C coatings, glass, plastics, and PVD coatings.
L-6240 is an LED-curable UV resin characterized by high hardness, high gloss, high cross-link density, and scratch resistance. Its application areas include coatings, inks, adhesives, OPV, plastics, paper, and nail gel.
For flooring and soft-touch applications, L-6316 combines leveling and fullness with fast response and scratch resistance, while L-6360 provides wetting, scratch resistance, slipperiness, toughness, and anti-yellowing characteristics for PVC flooring, paper, plastics, and wood.
L-6365 is another option where fast curing, scratch resistance, and substrate adhesion are important.
Matte and Soft-Touch UV Resins
Scratch resistance becomes more challenging when the coating also needs a low-gloss or soft-touch appearance.
L-6380A provides a gloss range of approximately 5°–10°, high hardness, and scratch resistance while maintaining a smooth soft-touch film. It is designed for matte OPV, PVC flooring, leather, plastics, and inks.
Related grades include L-6380A-4, which adds a low-odor characteristic, and L-6380A-10, which provides an anti-yellowing characteristic.
L-6380M is an anti-scratch matte resin designed for a stable 1°–3° gloss level without haze, together with compatibility, leveling, and adhesion properties.
High-Abrasion and Specialty Grades
For applications requiring stronger abrasion resistance, L-6900 provides high scratch resistance together with weather and yellowing resistance at functionality 9.
L-6902 and L-6902X, with functionality 15, reference steel-wool resistance of more than 5,000 times, together with weatherability and yellowing resistance.
For anti-graffiti and anti-fingerprint applications on plastics and films, the L-6905 series provides additional specialty options.
In dual-cure applications, L-8469 combines steel-wool resistance, fast surface drying, low shrinkage, and high hardness for applications including inks, mobile phone glass, and automotive interiors.
Scratch Resistance Also Depends on the Complete Formulation
Selecting a scratch-resistant UV resin is only one step in formulation development. Monomers affect flexibility, viscosity, and cross-linking behavior; photoinitiators influence cure response; additives can modify wetting, leveling, slip, and surface properties; pigments and fillers can also change the mechanical behavior of the cured film.
Substrate preparation and coating thickness are equally important. A resin that performs well on glass may not provide the same result on PVC, PC, leather, or a soft-touch substrate.
For this reason, formulators should compare candidate resins under the same formulation and processing conditions rather than relying on a single specification.
How Should Scratch Resistance Be Evaluated?
Testing should reflect the actual application. Depending on the end use, evaluation may include:
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Scratch or abrasion resistance
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Steel-wool resistance
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RCA resistance
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Surface hardness
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Adhesion
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Flexibility or bending resistance
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Gloss and appearance retention
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Chemical and weather resistance
The test method, load, number of cycles, film thickness, curing energy, and substrate should be recorded when comparing different formulations.
A System-Based Approach to Scratch-Resistant UV Coatings
There is no single UV resin that provides the same scratch performance across every application. Effective formulation development starts with the target substrate and required surface properties, then considers resin functionality, hardness-flexibility balance, curing method, and the interaction of monomers, photoinitiators, and additives.
Guangdong Lencolo New Material Co., Ltd., operating under the Lencolo brand, provides UV resin grades across multiple functionality and application categories. Its UV resin portfolio includes 167 grades across 16 product families, with technical data covering functionality, viscosity, key properties, and typical applications.
For formulators developing scratch-resistant coatings, inks, adhesives, flooring finishes, electronics coatings, or automotive interior surfaces, this type of application-specific resin selection provides a more practical starting point than choosing a material based on “high hardness” or “scratch resistance” alone.
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Guangdong Lencolo New Material Co., Ltd.
