2025 UV Curing Principle

Olá a todos! Sou uma funcionária estrela da CHROMÉCLAIR, uma marca de marcas de esmaltes em gel sem hema.Today, I’ll organize some information about UV curing. I hope this helps you.

UV adhesive curing occurs when photoinitiators (or photosensitizers) within UV-curable materials absorb ultraviolet light, generating active free radicals or cations. These trigger chemical reactions such as polymerization, cross-linking, and grafting of monomers or oligomers, transforming the liquid into a solid within seconds.

Each type of UV light has a distinct wavelength range, which determines its penetration depth into substrates. The appropriate UV light can be selected based on the substrate material used and the desired curing effect:

UVC is a short-wavelength ultraviolet light (200nm-280nm) that delivers strong output in the 250-260nm range but has poor propagation through air. Since oxygen can block UVC, many applications involve the use of nitrogen-purged environments. Primarily used for top-surface curing, it produces surface hardness and abrasion resistance (UVC imparts scratch resistance to coatings). Common uses include: transparent coatings on paper and plastic surfaces; hard coatings for optical and automotive lenses; disinfection and sterilization applications; DNA cross-linking; surface modification.
UVB is a medium-wave ultraviolet (280nm-320nm) capable of deep penetration curing, creating coating and adhesive toughness. Common applications include: curing paints, adhesives, and inks; sterilization and disinfection.
UVA is a long-wave ultraviolet (320nm-395nm) used for curing the deepest layers and providing adhesion. Common applications include: curing inks, coatings, and adhesives; UV inspection; UV fluorescence.
UVV is visible-light UV (395nm–455nm), used for curing the deepest areas and responsible for the adhesion properties of these formulations. UVV works well with white and silver conductive pigments. Common applications include: silver conductive inks; titanium dioxide pigment coatings; adhesives and deep-penetrating potting compounds.

UV Curing vs. Thermal Drying

In industrial processes, two popular drying/curing methods are thermal drying and UV curing. Both methods transform liquid or semi-liquid materials into solid form through heating or ultraviolet radiation. While both aim to cure substances, significant differences exist between them.

Thermal drying is a process that applies heat to ink or coatings on a substrate to accelerate their curing time. It is commonly used for substances like epoxy resins, powder coatings, and certain types of adhesives. It can also be applied to various coatings such as epoxy, polyester, acrylic, and polyurethane, which can be applied to substrates including metals, plastics, and composites.

Heat is typically supplied via large gas-fired ovens, forced-air dryers, or infrared lamps. The curing temperature and duration depend on the specific material being cured. Drying lines can be extensive, tailored to the target production speed and drying time requirements of the ink or coating.

Additionally, certain coatings may require special formulations to ensure proper drying during thermal curing. For instance, some coatings might need the addition of drying agents or accelerators to enhance drying efficiency or reduce drying time.

In terms of energy consumption and production efficiency, UV curing technology consumes significantly less energy than thermal drying technology. The energy consumption of UV curing is only 10%-20% of that required by thermal curing processes. This substantial energy gap primarily stems from UV curing’s high energy conversion efficiency: UV light sources convert most input energy into usable ultraviolet light, whereas thermal drying inevitably loses substantial thermal energy during heat transfer.

UV curing technology also excels in production efficiency. Its curing speed is exceptionally fast, typically completing the process in just 0.1 to 10 seconds. In contrast, thermal drying technology often requires several minutes or longer to achieve the same curing effect. This substantial time difference directly impacts production efficiency, making UV curing technology particularly suitable for high-speed production lines and batch manufacturing.

UV-cured coatings typically exhibit higher crosslinking density, directly leading to superior mechanical properties and chemical resistance. For instance, UV-cured coatings often demonstrate greater hardness, enhanced impact resistance, and outstanding chemical resistance. These characteristics make UV curing particularly suitable for applications requiring long-term outdoor exposure, such as architectural exterior coatings or protective automotive component coatings.

However, UV curing technology may have limitations in certain specific applications. For instance, when handling thicker coatings, UV curing may encounter uneven curing issues due to the limited penetration capability of UV light. In such cases, thermal drying technology may be more suitable as it better accommodates thicker coatings.

Simultaneously, thermal drying technology is expanding into emerging fields. For example, in new energy material manufacturing, thermal drying can be employed for drying battery electrode materials, ensuring material uniformity and conductivity.

Overall, the choice between thermal drying and UV curing ultimately depends on the specific application, and factors such as speed, durability, and environmental impact should be considered.

UV LED and Traditional Mercury Lamp Curing

Both UV LED and traditional mercury lamp curing rely on light irradiation to excite photoinitiators, thereby promoting the polymerization reaction of monomers and prepolymers contained within the fluid. This process results in the formation of a hardened film layer.

Compared to UV curing, UV-LED technology consumes only one-quarter of the electrical energy, significantly reducing energy consumption and CO2 emissions.

Traditional mercury lamps easily exceed radiation levels of 10W/cm², causing excessive heat during surface curing. In contrast, UV-LED radiation energy is controllable and generates minimal heat. This results in reduced thermal impact on heat-sensitive substrates like plastic films, requiring only minor adjustments to printing precision.

UV-LED light source components have a lifespan approximately 12 times longer than traditional UV components, substantially reducing replacement frequency and associated material costs.

UV-LEDs enable instant on/off operation, eliminating the preheating and cooling times required for UV curing, thereby enhancing operational efficiency.

UV-LED systems produce no ozone, improving the working environment for employees and eliminating the need for capture and incineration equipment to mitigate ozone hazards.

UV-LED light sources and their associated equipment are highly compact, simplifying setup and saving space. As evident from these advantages, UV-LED curing systems not only significantly reduce costs but also minimize environmental pollution and energy consumption.

However, unlike traditional UV curing that utilizes the entire 200–450 nm ultraviolet spectrum, UV-LED lamps focus on a narrow range within this spectrum, typically 395–405 nm. While some current UV-LED curing systems operate at 365 nm, most still center around 395 nm, which remains the standard wavelength for UV-LED curing.

We hope this article helps you understand UV curing more easily!

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