Scratch resistance is an important performance requirement for UV-curable coatings used on plastics, glass, wood, PVC/SPC flooring, 3C electronics, automotive interiors, and other frequently handled surfaces. However, improving scratch resistance is not simply a matter of choosing a high-hardness resin.
The final performance of a UV coating depends on the interaction between UV resin chemistry, cross-link density, hardness, flexibility, curing conditions, formulation components, film thickness, and substrate characteristics. A resin that performs well in one application may require a different formulation approach on another substrate.
What Determines Scratch Resistance in UV Coatings?
UV resin is a major film-forming component in a UV-curable formulation. Its functionality, chemical structure, viscosity, curing response, hardness, flexibility, adhesion, and surface characteristics can all influence the final coating.
Resin Functionality and Cross-Link Density
Functionality affects the network structure formed during UV curing. Higher-functionality oligomers can produce a denser cross-linked network, which may contribute to higher hardness and resistance to surface marking.
However, increasing functionality is not automatically the solution. 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 products ranging from difunctional grades to resins with functionality up to 15, providing different options for formulation development.
Hardness and Flexibility
Scratch resistance needs to be considered together with mechanical flexibility. A very hard film may resist certain scratching or abrasion tests but can crack when the substrate bends or experiences impact. A softer film may tolerate deformation better but can be more susceptible to surface marking.
Rigid substrates such as glass may require a different resin balance from flexible plastics, leather, or soft-touch coatings.
Curing Conditions
Mercury UV, UV LED, Excimer, and Dual Cure systems can produce different curing profiles and surface properties. The resin, photoinitiator system, UV wavelength, energy, and exposure conditions must therefore be considered together.
Incomplete or uneven curing can reduce surface hardness and make the coating more vulnerable to scratching, even when the selected resin has good scratch-resistance characteristics.
Lencolo UV Resins for Scratch-Resistant Applications
Several UV resin grades in the Lencolo portfolio have documented scratch, wear, or abrasion-related characteristics. These products are candidate materials for formulation evaluation rather than universal solutions.
Polyurethane Acrylates
L-6207 combines wear resistance and flexibility with fast curing and RCA resistance of more than 200 times. Its application areas include 3C coatings, glass, plastics, and PVD coatings.
L-6240 is an LED-curable UV resin featuring high hardness, high gloss, high cross-link density, and scratch resistance. It is used in coatings, inks, adhesives, OPV, plastics, paper, and nail gel.
For flooring and soft-touch applications, L-6316 combines high leveling and fullness with fast response and scratch resistance for SPC/PVC flooring and soft-touch plastics. L-6360 combines wetting, scratch resistance, slipperiness, toughness, and anti-yellowing characteristics for PVC flooring, paper, plastics, and wood.
L-6365 provides another option where fast curing, scratch resistance, and substrate adhesion are required.
Matte and Soft-Touch UV Resins
Low-gloss coatings create an additional formulation challenge because the surface must maintain its appearance while resisting scratching and marking.
L-6380A is designed around a 5°–10° gloss range, high hardness, and good scratch resistance while maintaining a smooth soft-touch film. It is used for matte OPV, PVC flooring, leather, plastics, and inks.
Related grades include L-6380A-4, which provides 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 with more demanding abrasion requirements, L-6900 provides high scratch resistance together with weather and yellowing resistance at functionality 9.
L-6902 and L-6902X, both at functionality 15, reference steel-wool resistance of more than 5,000 times, together with weatherability and yellowing resistance.
The L-6905 series extends the performance focus to anti-graffiti and anti-fingerprint coatings for plastic and film substrates.
For 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 Depends on the Complete Formulation
UV resin selection is only one part of the formulation. Monomers influence viscosity, flexibility, and cross-linking behavior. Photoinitiators affect curing response, while additives can modify wetting, leveling, slip, and other surface characteristics. Pigments and fillers can also change the mechanical behavior of the cured film.
Substrate preparation and coating thickness are equally important. A formulation that performs well on glass may not produce the same result on PVC, PC, leather, or a soft-touch substrate.
For this reason, candidate resins should be compared under consistent formulation and processing conditions rather than selected from a single specification.
How Should Scratch Resistance Be Tested?
The testing method should match the intended application. Depending on the coating system, 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 retention
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Chemical resistance
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Weathering performance
Test results should be interpreted together with film thickness, substrate, curing energy, curing method, load, and number of cycles. This helps prevent misleading comparisons between products tested under different conditions.
A System-Based Approach to UV Coating Selection
Improving scratch resistance requires more than selecting a resin with a high-hardness or anti-scratch description. Formulators need to consider the target substrate, required surface properties, resin functionality, hardness-flexibility balance, curing technology, and interactions among the other formulation components.
Guangdong Lencolo New Material Co., Ltd., operating under the Lencolo brand, offers UV resin grades across multiple functionality levels and application categories. Its portfolio includes 167 UV resin grades across 16 product families, with technical information covering functionality, viscosity, key characteristics, and typical applications.
For formulators developing scratch-resistant coatings, inks, adhesives, flooring finishes, electronics coatings, or automotive interior surfaces, selecting UV resin according to the complete application system provides a more reliable development path than evaluating scratch resistance as an isolated resin property.
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Guangdong Lencolo New Material Co., Ltd.
