Environmental concerns and technical advancements are drawing closer the days when UV-activated coatings are regularly used in your shop
The continued reduction of volatile organic compounds (VOCs) remains one of the leading areas of research as environmental concerns related to air quality remain a priority. Automotive and paint coating manufacturers, along with the collision repair industry, continue to develop ways to reduce the environmental burden. High volume-low pressure (HVLP) spray equipment, for instance, was an initial effort by manufacturers and the collision repair industry to reduce VOCs. Consequently, coating formulas were changed to increase the amount of solids and decrease the amount of solvent in coatings. In the past few years Europe and Canada have adopted the use of waterborne basecoat coatings, reducing the environmental load even more. California soon will join them, and it is widely suspected that the remainder of the United States will adopt similar waterborne basecoat requirements.Waterborne basecoat in use today continues to use traditional solvent-laden undercoats and clearcoats. One way to further reduce VOCs is by using ultraviolet-activated undercoats and clearcoats. Though ultraviolet-activated coatings are not VOC-free, they contain significantly smaller amounts, and would greatly benefit the environment if used.
Ultraviolet (UV) paints have an ingredient called a photoinitiator that acts similarly to catalysts and hardeners used in traditional epoxy or polyurethane solvent-based paints. The photoinitiator will react with ultraviolet energy, causing the coating to crosslink very rapidly compared with traditionally hardened paints. The UV light transfers energy through the air in small units called photons. When photons strike photoinitiators within the coating, the paint film will harden uniformly. The trick is getting the photons to hit all the photoinitiators. If the film build is too high or in the presence of energy-blocking pigment, the photons will not reach the photoinitiators and thus the coating will not cure completely.Presently, undercoats and clearcoats are available in UV-activated coatings, though color coatings are still in their infancy, and clearcoats are limited to the size of the light available to the technician. UV-activated primer is the most advanced, and is available in an aerosol and sprayable coatings. Primer is sprayed eight to 10 inches away from the panel, and after the recommended amount of coats with a short flash time between coats, the required film build is achieved. A UV light is applied to the surface, and after the recommended amount of exposure (in some cases as little as two minutes), the undercoating can be sanded and top-coated.
Some UV-activated coatings have a fluorescing agent, so the operator can monitor the coating as it cures. When first developed, UV primers hardened with a tacky film that remained uncured because of the presence of oxygen at the paint surface. The technician then wiped off this film with an alcohol-based cleaner. Now primers are available that don't leave an uncured film on the top surface and can be sanded or top-coated immediately after curing.Using UV-activated paints has many environmental benefits. UV paint does not harden until exposed to UV energy, so cleanup is easy and quick, since it is still liquid. Additionally, the technician does not have to clean out the paint gun that sprays UV paint, but just hang the gun up in an area not exposed to UV energy. Cosmetic cleanup of the gun is accomplished by wiping the gun with a towel dampened with thinner to clean off the air cap and tip. This eliminates the need to use a significant amount of thinner to clean the gun after each use.
Since paint is cured by a light and not by heat, a baking would no longer be necessary either. This also will save energy costs, as the paint booth only needs to be heated to a comfortable room temperature for the painter.The time factor is another positive aspect of using UV-activated paints. The UV primer and clearcoats offer a cure time of two to five minutes. This significantly speeds up the painting process, as the primed repair can be wet-sanded immediately with minimal waiting time for the panel to cool down. A panel coated with UV clear can be buffed and polished immediately after the curing process is complete. Saving a few minutes of downtime in each step can add up significantly and improve productivity at a shop. For example, if a shop averages 14 work hours per job, it can reduce this time to 10 hours per job by just switching to UV-activated paints. If a shop has four technicians that work 40 hours a week, they can do 160 hours of work per week. At 14 hours per job, the shop would average 11.5 jobs per week. But reducing the time to 10 hours per job would boost output to an average of 16 jobs per week.
Minimal technical adjustment is needed to switch from using solvent-based paints to UV paints. A downdraft booth is still needed to move overspray away from the paint finish; paint respirators still need to be worn; and the same HVLP paint guns used to spray solvent-based paints can be used to spray UV paints. The biggest change required is purchasing and setting up the ultraviolet lights to cure the paint finishes. Small, easily moved light stands can be used for small-area repairs, though bigger lamps may be needed for curing larger repairs consisting of two or more panels. A formidable challenge that remains with today's technology is the development of practical UV lamps suitable for collision repair applications.UV paint repairs are presently limited to spot repairs, unless the shop has more than one UV light to cure larger areas. Currently, the size of a single light needed to cure clearcoat on a multiple-panel repair would be too large to be mobile. In addition, the screens of UV lights need to be meticulously cleaned daily, to ensure that the UV light is distributed evenly on the surface of the repair. As to results, after the paint has cured with a UV light, some masking adhesives may not release as well as when baked, and may be very difficult to remove without peeling away some of the paint's finish.
With these current limitations, it may seem that using UV-activated coatings will not be practical for many years in the automotive aftermarket industry. If these coatings are being used alone this might be true, but when coupled with readily available waterborne basecoats, UV undercoats and clearcoats may be the answer to solving automotive and aftermarket refinish VOC emissions problems.
The disadvantages of UV-activated paints are being continually reduced as the technology is improved, but they are still present. Though the technical adaptations that must be made to change from the use of solvent-borne coatings to UV-activated coatings are minimal, it may take some time for technicians to adjust to the changes. In terms of safety equipment, protective eyewear must be worn when working with a UV lamp to protect the eyes from the UV rays.As everyone including regulators, coatings manufacturers, shop managers, community leaders and neighborhoods strive for environmental improvements each year, solvent-based paints may be in their last days. Meanwhile, with advancements in waterborne basecoats, combined with the improvements of UV primer coats and clearcoats, the practicality of regularly using UV-activated coatings is drawing nearer. As the technology for UV lamps becomes more affordable and UV paint suppliers become more common, it may be a wise decision for shops to start the transition from solvent-based paints to waterborne and UV paints before it is mandatory.
