UV Curing Technology
UV Curing is a photochemical process by which specially formulated liquid monomers are polymerized, or “Cure” by exposure to ultraviolet radiation.
The UV-Curable monomers contain sensitizes that absorb UV energy which then produce very rapid polymerization.
The relative speed of curing depending on several factors, including the chemical formulation and thickness of the monomer, and the intensity and spectral distribution of the ultraviolet source.
What is Ultraviolet Light Ultraviolet radiation cover a band of wave lengths just beyond the eye’s capabilities. This Board band of the UV Spectrum is divided into three ranges:
Future distinctions in wave lengths are often made to define their application :
It shows that the curing band can encompass the complete UV spectrum depending on the particular job that it has to do.
Advantages of UV Curing
High Productivity fast curing can be achieved at ambient temperatures there by shortening production times and minimizing stacking.
Energy Serving : UV Curing consumes only 20% of the energy needed to cure solvent-based coatings.
No Air Pollution : UV Curable materials are “Solvent Free” and therefore do not release residues or gases into the environment.
Low Heat Output : Because ultraviolet, instead of infrared radiation is used, fragile materials such as paper, plastic and thin films can be processed safely.
Space Saving : UV Systems are usually smaller in size than their conventional counterparts.
UV Curing Applications
New uses of UV Curing are being developed everyday. Among them most wide used are :
– Plating Ink
– Screen Printing On Glass
– Printed Circuit Boards
– Graphic Art
– Metallic Decorations
– Plaint Drying of Plywood
– Setting Adhesives
– Surface hardening
– Photolysis of Toxic Waste
UV Curing Units
There are three types of cooling systems.
Combined Air and Water Cooling
Cooling systems for the material to be coated can be added, for example: water plates for the label printing machines.
Most important for the cooling is :
Optical lamp cooling about 600C-900C lamp tube temperatures. If the temperature is too high, the result is diversified , especially in combination with impurities.
At temperatures above 1000C the quartz soften and the lamp blows up or will bend under it’s own weight. It is also important to have the correct temperature at the sealing. It should not exceed 350C. If the temperature is too high, the sealing foil might oxidize and the lamp will lose its vacuum.
Ozone must be removed so that the KAM-value of 0.1 PPM will not exceed. Ozone is unstable and will disintegrate into oxygen after a few minutes.
The picture below shows the most common type of air-cooling. The hot air above the lamp is removed and fresh air can get the housing. Air flow should be between 30m/h – 50m/h depending on lamp Kw.