Achieving both high hardness and good flexibility is a common challenge in UV-curable coatings, inks, adhesives, and transfer materials. A hard surface can improve scratch and wear resistance, but excessive rigidity may cause cracking during bending or impact. In contrast, a flexible film may withstand deformation but provide insufficient surface durability.
This balance is important in 3C electronics, PVD coatings, plastic finishing, SPC flooring, wood coatings, and specialty adhesives. The right solution depends on resin chemistry, formulation design, substrate properties, and curing conditions—not on a single performance specification.
Start with Application Requirements
UV resin is a major film-forming component that influences hardness, flexibility, adhesion, viscosity, curing behavior, and surface performance. Resin functionality affects the potential cross-link density of the cured film, but higher functionality does not automatically produce a better result. Excessive cross-linking may increase hardness while reducing flexibility or increasing brittleness.
The target balance should be defined by the application. Glass and metal coatings may prioritize hardness and scratch resistance, while leather, TPU, and flexible films require elasticity and adhesion during deformation. Flooring and plastic coatings often need a combination of wear resistance, toughness, appearance, and cost efficiency.
Resin Candidates for Hardness and Flexibility
Different resin structures provide different starting points for formulation development. Modified epoxy acrylates may offer film formation and hardness, while polyurethane acrylates can support combinations of mechanical strength, flexibility, and adhesion.
L-6113 is a modified epoxy acrylate UV resin described as offering fast curing, excellent film formation, soft elasticity, high hardness, and good scratch resistance. With a functionality of 4 and a viscosity of 800–1,500 CPS, it is indicated for coatings and inks involving wood, paper, plastic, and metal, as well as OPV, PVD, and 3D printing.
L-6207 is a two-functional polyurethane acrylate positioned around wear resistance, flexibility, fast curing, and RCA resistance exceeding 200 times. It can be evaluated for 3C coatings, glass, plastic, and PVD applications.
L-6390 combines documented water and heat resistance, adhesion, and a balance of flexibility and hardness. Its indicated applications include 3C coatings, DIY adhesives, SPC flooring, nail polish, and 3D printing.
L-6601A is a six-functional polyurethane acrylate described as offering a high curing rate, hardness, flexibility, and temperature resistance. Its organotin-free related grade, L-6601D, may be considered for formulations with specific raw-material requirements.
For hard-texture transfer coatings, L-8403 is positioned around low shrinkage, flexibility, hardness, and pigment wettability. It is indicated for adhesives, inks, coating-film transfer, and nail gel applications.
These products should be treated as candidate materials rather than universal solutions.
How the Complete Formulation Influences Performance
The final hardness-flexibility balance depends on more than the selected resin. Reactive monomers influence viscosity, reactivity, cross-linking, shrinkage, and flexibility. Photoinitiators affect curing efficiency and must match the light source, film thickness, and formulation system.
Additives, pigments, and fillers may change flow, dispersion, surface appearance, adhesion, and mechanical properties. A resin that performs well in a clear coating may behave differently in a pigmented ink, matte coating, or filled adhesive.
Curing technology also matters. Mercury UV, UV LED, excimer, dual-cure, moisture + UV, and UV + thermal or 2K systems can produce different curing profiles. Surface hardness, through-cure, shrinkage, and flexibility should be evaluated under actual processing conditions.
Testing and Material Selection
When comparing candidate UV resins, formulators should evaluate hardness and flexibility together with adhesion, scratch resistance, abrasion, chemical resistance, yellowing, and shrinkage. Testing should reflect the actual substrate, application method, film thickness, viscosity, and curing equipment.
Guangdong Lencolo New Material Co., Ltd., operating under the Lencolo brand, provides technical reference formulations and process parameters marked “Status: Verified” and “Usage: Reference only.” These references can support preliminary development but must be reassessed when application or curing conditions change.
A reliable selection process begins with the application requirements, identifies suitable resin structures, and then evaluates the complete formulation through comparative trials. Lencolo’s catalog includes 167 UV resin grades across 16 product families, offering different starting points for hardness-flexibility development. Final suitability should always be confirmed through testing under the customer’s actual project conditions.
https://www.lencolo37.com/
Guangdong Lencolo New Material Co., Ltd.
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