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Achieving both hardness and flexibility is a common formulation challenge in UV-curable coatings. A hard film may provide good scratch resistance but crack when bent or exposed to impact. Conversely, a flexible coating may withstand deformation while offering insufficient surface durability. The solution is not simply to choose a resin with the highest hardness or flexibility rating, but to understand how the resin works within the entire coating system.
UV resin contributes to film formation, curing behavior, adhesion, surface performance, and mechanical properties. Its interaction with monomers, photoinitiators, additives, pigments, fillers, and the substrate determines how the cured film performs in practice.
Why Resin Selection Requires More Than a Specification Sheet
Hardness and flexibility are influenced by several formulation and processing variables, including resin functionality, molecular structure, monomer selection, film thickness, curing energy, and substrate properties. Application requirements also differ considerably. A UV coating for a rigid plastic component may prioritize scratch resistance and surface hardness, while a coating for a flexible film or transfer application may require greater elongation and adhesion.
Viscosity, wettability, chemical resistance, water resistance, yellowing resistance, and curing speed should therefore be evaluated alongside mechanical properties. A resin that performs well in one formulation may not deliver the same results when the substrate, application method, or curing conditions change.
UV Resin Grades to Consider for Hardness-Flexibility Development
Guangdong Lencolo New Material Co., Ltd., operating under the Lencolo brand, offers UV resin grades for coatings, inks, adhesives, PVD, 3D printing, and other applications. Several products in its catalog provide useful starting points for formulations requiring a combination of surface durability and flexibility.
L-6113 – Modified Epoxy Acrylate
This low-viscosity, four-functional epoxy acrylate is described as offering fast curing, excellent film formation, soft elasticity, high hardness balance, and good scratch resistance. Its viscosity is 800–1,500 CPS, with applications including wood, paper, plastic, and metal coatings, inks, OPV/PVD, and 3D printing.
L-6207 – Two-Functional Polyurethane Acrylate
L-6207 is designed around balanced wear resistance and flexibility, together with a fast curing rate. It features RCA resistance over 200 times, a functionality of 2, and viscosity of 28,000–38,000 CPS. Typical applications include 3C coatings, glass, plastic, and PVD.
L-6390 – Four-Functional Polyurethane Acrylate
For applications requiring a combination of mechanical balance and environmental resistance, L-6390 provides good flexibility and hardness, adhesion, water resistance, and heat resistance. It has a functionality of 4 and viscosity of 4,000–8,000 CPS at 60°C. Its application range includes 3C coatings, DIY glue, SPC flooring, nail polish, and 3D printing.
L-6601A and L-6601D – Six-Functional Polyurethane Acrylates
L-6601A is positioned for high curing speed, high hardness and flexibility, and temperature resistance. It is used in PVD, gloss varnishes, inks, DIY glue, 3D printing, and plastic applications. L-6601D offers a related organotin-free option, with low-viscosity positioning and the same high-hardness-and-flexibility focus. Actual suitability depends on the formulation and applicable organotin requirements.
L-8403 – High-Performance Polyurethane Acrylate
L-8403 is intended for hard-texture transfer coatings and offers low shrinkage, good flexibility, good hardness, and pigment wettability. With a functionality of 2 and viscosity of 20,000–50,000 CPS, it can be considered for transfer films, adhesives, inks, coatings, and nail gel applications.
How to Evaluate a Resin in the Complete Formulation
Resin-level descriptions provide a starting point, but they cannot predict finished-film performance under every condition. When developing a formulation, consider the interaction between the resin and reactive monomers, photoinitiators, additives, pigments, fillers, and any other components.
The curing process is equally important. Mercury UV, UV LED, excimer combined with UV, dual cure, moisture plus UV, and UV combined with thermal or 2K curing systems may produce different performance outcomes. Film thickness, curing dose, line speed, and substrate surface characteristics should be considered during evaluation.
For example, a resin intended for a rigid PVD coating may require a different balance of hardness, adhesion, and flexibility than one used in a transfer coating or flexible plastic application. Comparing products under the same test conditions can help identify meaningful differences between candidate grades.
A Practical Approach to Product Selection
Before selecting a UV resin, define the application requirements as clearly as possible:
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Substrate: Plastic, glass, metal, wood, paper, film, or flooring.
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Application method: Spray, roller, curtain coating, printing, dipping, or adhesive application.
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Curing system: Mercury UV, LED UV, excimer, dual cure, or another process.
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Performance targets: Hardness, flexibility, scratch resistance, adhesion, chemical resistance, and weathering performance.
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Processing requirements: Viscosity, film thickness, curing speed, and production conditions.
When these details are unavailable, a preliminary comparison of resin grades may still be possible, but the selection should remain subject to further technical review.
Conclusion
Balancing hardness and flexibility in UV coatings requires a system-level approach rather than a single-property comparison. Epoxy acrylates and polyurethane acrylates can provide different formulation directions, while functionality, viscosity, curing conditions, and substrate compatibility help determine their practical suitability.
Lencolo's grades, including L-6113, L-6207, L-6390, L-6601A, L-6601D, and L-8403, offer documented starting points for different coating, ink, adhesive, PVD, and transfer applications. Final performance should be established through formulation trials and application-specific testing, supported by relevant technical data and process information.
https://www.lencolo37.com/
Guangdong Lencolo New Material Co., Ltd.
