Analysis of Physical Properties of UV Curing Materials

The physical properties of UV-cured materials are essentially affected by the drying system used to cure them. The expected performance gains, whether protective gels, inks, or adhesives, will depend on the parameters, design, and control of these lamps. The four key parameters of the UV lamp are:

1. UV radiation (or density)

2. Spectral distribution (wavelength)

3. Radiation (or UV energy)

4. Infrared radiation. With respect to the maximum radioactivity or amount of radiation, as well as different UV spectra, inks and protective adhesives will exhibit very different characteristics. The ability to identify different UV lamp properties and match them to the optical properties of the curable material expands the scope of UV curing as a fast and efficient manufacturing process. Many of the curing system's optical and physical properties (in addition to its own composition) affect the curing effect, resulting in differences in the UV cured material's performance.

Cured material properties

The efficiency of a UV lamp depends on how easy it is to launch photons into a curable material to initiate light triggering the molecule. UV curing is determined by photon-molecule collisions. Light can trigger molecules to spread evenly through the material, but the photons are different. In addition to the characteristics of the UV light source, the cured film has optical and thermodynamic properties. They interact with radiant energy and have a major impact on the curing process.

Spectral Absorption: Energy is the absorption of a substance into a wavelength in a gradually increasing thickness. The more energy absorbed near the surface, the less energy is obtained in the deep layer. However, this situation varies with the wavelength. The total spectral absorbance includes all effects from light triggers, single molecules, oligomers, and additives including pigments.

Reflection and Scattering: Relative to absorption, light energy is more often redirected by a substance (or within a substance); this is generally due to the matrix material and/or pigment in the curable material. These factors reduce the UV energy reaching deeper, but improve the curing efficiency at the reaction.

Optical density: Similar to absorption, it consists of two factors: "opacity" and the thickness of the film; including photodilution of absorption and scattering; expressed by a single number, not as a distribution of the spectrum.

Diffusion: A thermodynamic property that contains specific heat, conductivity, and density; the ability of a material to “diffuse” and accept heat; and the temperature of a film and substrate that is affected by infrared energy that suddenly enters the surface.

Infrared Absorption Rate: Temperature has a significant effect on the rate of curing reaction; although the temperature rise in the reaction also affects the temperature, the radiation from the UV lamp (radiant IR) is the fundamental source of surface heat (not from the surrounding Air or heat transferred in the atmosphere). Excessive temperature increase is one of the important limiting factors affecting the curing process.

Optical thickness coating and ink

Due to the fact that opacity or color intensity is a characteristic we need, inks and pigment coatings pose special problems. Adhesives generally also provide a relatively thick film. Unlike the physical thickness of a film, its optical thickness is very important. When light penetrates or passes through a material, its reduction is described by the Beer-Lambert—the light energy that is not absorbed by the upper layer of the film and that is not reflected will pass through to the bottom layer of the film.