What Is the Difference Between UV Ozone Type and Ordinary Shoe Sole UV Curing Machine

Shoe sole UV treatment equipment falls into two fundamentally different categories that are often confused: UV ozone type machines and ordinary UV curing machines. The difference is not simply a matter of configuration or power-it comes down to the wavelength of ultraviolet light they emit, the chemical processes they trigger, and the surface changes they produce on the sole material.

The Core Difference: Wavelength

The distinction begins with the lamps inside each machine.

Ordinary shoe sole UV curing machines use high-pressure mercury lamps that emit primarily at 365nm in the UVA range . This wavelength is optimized for photoinitiator activation-it triggers the cross-linking of UV primers and adhesives that contain photo-reactive chemicals .

UV ozone type machines use low-pressure mercury lamps that emit at 184.9nm and 253.7nm in the deep UV range . The 184.9nm wavelength carries enough photon energy to split oxygen molecules (O₂) and generate ozone (O₃) continuously within the treatment chamber. The 253.7nm wavelength then decomposes the ozone into atomic oxygen and other reactive species .

The two machine types are not interchangeable. A 365nm lamp cannot generate ozone, and a 184.9nm lamp is not optimized for primer curing.

What Each Machine Actually Does

Ordinary UV Curing Machine: Activates Primer

The ordinary UV curing machine's job is to cure a primer layer. The process requires that a chemical primer-typically containing photoinitiators, acrylate monomers, and chlorinated polyolefin resins-be applied to the sole surface first. When the primed sole passes under 365nm UV light, the photoinitiators absorb the energy, decompose into free radicals, and initiate polymerization of the primer film . The cured primer creates a polar layer that adhesives can bond to.

Without primer, the 365nm machine does very little to the EVA surface itself.

UV Ozone Machine: Modifies the Surface Directly

The UV ozone machine does not require a primer to change the EVA surface. Instead, it uses the combination of deep UV photons and ozone to chemically and physically modify the sole material itself.

The 184.9nm photons have sufficient energy to break carbon–carbon and carbon–hydrogen bonds on the polymer surface . Simultaneously, the ozone and atomic oxygen generated by the lamp react with these broken bonds, creating new polar functional groups: carbonyl (C=O), hydroxyl (–OH), and carboxyl (–COOH) . These groups raise the surface energy of the EVA, allowing adhesives to wet and bond to the material.

The process also produces ablation and etching. Research using scanning electron microscopy shows that UV-ozone treatment creates a "ruffled" topography with deep crevices on EVA-PE surfaces . This mechanical interlocking complements the chemical bonding. For EVA containing 20% vinyl acetate, ablation is dominant; for EVA containing 12%, roughness formation prevails .

What the Surface Modification Achieves

The practical outcome differs in measurable ways.

A study on EVA-PE blends used in sport soles found that UV-ozone treatment produced "noticeably increased" adhesive strength in joints made with polyurethane adhesive . The failure mode shifted from adhesive failure at the EVA-adhesive interface to cohesive failure within the leather substrate-meaning the bond became stronger than the materials it was joining.

For EVA12 bonded with polychloroprene adhesive, T-peel strength increased significantly after 5–7.5 minutes of UV-ozone treatment . The surface modifications lasted at least 24 hours after treatment, giving production flexibility .

A European patent specifically covering shoe sole treatment describes the process as applying UV radiation between 130 and 185nm at a power density of at least 20 mW/cm², with the sole placed inside a chamber containing ozone . The patent explicitly notes that this treatment is applicable to EVA, polyurethane foams, and vulcanized and non-vulcanized rubbers.

Why the Distinction Matters for Shoe Manufacturers

The choice between the two machine types depends on the chemistry of your bonding process.

If you use a UV primer: The ordinary 365nm curing machine is the correct choice. Its wavelength matches the photoinitiator absorption spectrum in standard UV primers.

If you want to eliminate primer or halogenation: The UV ozone machine offers a different path. It modifies the EVA surface directly, without requiring a chemical primer layer. A European patent contrasts this with traditional halogenation, noting that UV-ozone treatment "shortens treatment time from around one hour to minutes," produces "no chemical residues, nor are solvents used," and allows the adhesive to be applied immediately after treatment .

If you need deeper cleaning along with modification: UV ozone treatment also removes organic contaminants from the surface as a dry process, without chemicals or wet cleaning solutions .

Some production systems combine both approaches: a UV ozone chamber for surface activation, followed by primer application and a separate 365nm curing stage.

Summary

The two machines serve different roles in the bonding process. Understanding the wavelength difference-and what each wavelength does to the EVA surface-is the key to selecting the right equipment for your production line.