WHAT IS UV TECHNOLOGY?

Chances are... several times today you touched an object "cured" using ultraviolet (UV) processing by simply reaching for your morning cereal box, handling a CD or DVD, reading a magazine, using your credit card, typing on your keyboard, driving your car, or just walking on your floor.

UV refers to a special way in which coatings, inks and adhesives are cured or dried using “energy” from these sources, rather than conventional heat. In effect, the ultraviolet light spectrum in a UV lamp interact with specially formulated chemistries to cure materials typically more quickly, using less energy and thereby at lower cost than by other methods.

The advantages of UV have been well-documented -- particularly when used with manufactured products that include inks, adhesives and coatings on substrates that are sensitive to heat. In addition, UV is considered environmentally friendly since most of the solvents in inks, paints, adhesives and coatings can be eliminated, thanks to the special capabilities of UV curing.

What kind of substrates can UV coatings be used on?

Besides Concrete…it is used widely on Compact Discs, Hardwood Flooring, Upscale Shopping Bags, Optical Fibers, Furniture Laminates, Release Papers, Vacuum Metallized Plastic, Credit Cards, Beverage Cans, Photographic Film, Magazine Covers, Wall Paneling, Vinyl Floor Tile, Leather Finishes, Magnetic Media (tape & floppy disks), Galvanized Metal Tubing.

Also inks for: Lithographic, letterpress, flexographic, gravure and screen printing Adhesives for: Automotive headlamps, Pressure sensitive labels and decals, Potting and encapsulation of electronic components, Plastic components assembly for the medical industry.

Printing Plates: Letterpress, flexographic and gravure. Miscellaneous: Dental fillings, Rapid prototyping resins

THE UV CURING PROCESS

UV curing typically describes the use of ultraviolet (UV) or visible light to polymerize a combination of monomers and oligomers onto a substrate. The UV material may be formulated into an ink, coating, adhesive or other product.

The process is also known as radiation curing or radcure because UV is a radiant energy source. The energy source for UV or visible light cure are typically medium pressure mercury lamps, pulsed xenon lamps, LEDs or lasers.

Why Convert to UV Technology?

1. Improved Productivity: Most systems are solvent-free and require less than a second of exposure. Productivity gains are tremendous compared to conventional coating techniques. Web line speeds of 1,000 ft/min. are common and the product is immediately ready for testing and shipment.

2. Suited for Sensitive Substrates: UV coatings do not contain water or solvent. In addition, the process provides total control of the cure temperature making it ideal for application on heat sensitive substrates.

3. Environment and User Friendly: Formulations are solvent-free so emissions and flammability are not a concern. Light cure systems are compatible with almost all application techniques and require a minimum of space. UV lamps can usually be installed on existing production lines.

UV Curable Formula

Monomers are the simplest building blocks from which synthetic organic materials are made. A simple monomer derived from petroleum feed is ethylene. It is represented by: H2C=CH2. The symbol "=" between the two units or atoms of carbon represent a reactive site or, as chemists refer to it, a "double bond" or unsaturation. It is sites like these which are capable of reacting to form bigger or larger chemical materials called oligomers and polymers.

• Polymer: Is a grouping of many (i.e. poly-) repeat units of the same monomer. The term oligomer is a special term used to designate those polymers which often can be further reacted to form a large combination of polymers. The unsaturation sites on oligomers and monomers alone will not undergo a reaction or crosslinking.

When UV or visible light is utilized as an energy source, a photoinitiator is added to the mixture. The photoinitiator, when exposed to light, generates free radical or actions which initiate crosslinking between the unsaturation sites. These are the major components of UV.

• Oligomers: The overall properties of any coating, ink, adhesive or binder crosslinked by radiant energy are determined primarily by the oligomers used in the formulation. Oligomers are moderately low molecular weight polymers, most of which are based on the acrylation of different structures. The acrylation imparts the unsaturation or the "C=C" group to the ends of the oligomer.

• Monomers: Monomers are primarily used as diluents to lower the viscosity of the uncured material to facilitate application. They can be monofunctional, containing only one reactive group or unsaturation site, or multifunctional.

This unsaturation allows them to react and become incorporated into the cured or finished material, rather than volatilizing into the atmosphere as is common with conventional coatings. Multifunctional monomers, because they contain two or more reactive sites, form links between oligomer molecules and other monomers in the formulation.

• Photoinitiators: This ingredient absorbs light and is responsible for the production of free radicals or actions. Free radicals or actions are high energy species that induce crosslinking between the unsaturation sites of monomers, oligomers and polymers. Photoinitiators are not needed for electron beam cured systems because the electrons are able to initiate crosslinking.

• Additives: The most common are stabilizers, which prevent gelation in storage and premature curing due to low levels of light exposure. Color pigments, dyes, defoamers, adhesion promoters, flatting agents, wetting agents and slip aids are examples of other additives.

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