Collision Repair Training | United States
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Current Events/News: Advantage Online: 2002 Archives
ULTRAVIOLET-CURED PRIMER-SURFACER
March 4, 2002 -New primer-surfacer undercoats activated and cured by ultraviolet (UV) wavelength light provide an option for small repairs. UV-cured primer-surfacer is applied with an aerosol can. It cures in two minutes, and can be topcoated in 12 minutes. This process can take place outside the spraybooth or prep station as long as normal ventilation is available, and local regulations allow spraying a material in an open shop environment. Materials required for the process include the aerosol primer-surfacer and a special cleaner that's used after curing (see Figure 1). The cleaner is also available as a solvent wipe (see Figure 2).
The new chemistry of UV-cured primer-surfacer allows the UV wave to activate free radicals in the product, hold out oxygen, and cause rapid crosslinking of the resins. The fast crosslinking occurs without the need for hazardous chemicals like isocyanates. The result is a filler coating with exceptional adhesion, hardness, and resistance to solvents. Repair facilities of all sizes can benefit. Having the ability to apply primer-surfacer outside the confines of a spraybooth environment is an advantage in itself. Being able to apply the material and return to the repair in a matter of minutes can increase the productivity of the repair facility through increased workflow and the number of repairs without requiring additional floor space. There's also a reduction in the shuffling of vehicles, decreasing the required time in the facility.
There is a cost to this added convenience. The product requires the investment of the relatively costly UV drying lamp that can only be used with this product (see Figure 3). The aerosol can of primer-surfacer and the required cleaner are also relatively costly. This cost can be at least partially offset by not requiring time for mixing materials and cleaning equipment, the cost of cleaning supplies, and the limited amount of masking required. Trial sprays by the product maker show that one aerosol can will coat 8–12 repair areas the size of a large hand, with a film thickness of 5–6 mils.
The UV curing lamp cures an area the size of a sheet of paper using a "Halide" 250-watt bulb. This special bulb emits a form of halogen wavelength with an electropositive or radical element. This feature is the key to the fast crosslinking. Curing takes place in as little as two minutes. If the repair area is larger, the technician must move the lamp around, allowing each placement to remain the required amount of time, so that all areas are cured. A stand is available to roll the lamp to the next area and keep the lamp in one position for the required two minutes (see Figure 4). Undercured primer-surfacer can exhibit poor adhesion and also bleed or stain light colored topcoats. Overcuring is not a concern. Application Start the application of UV-cured primer-surfacer the same as applying most other types of primer-surfacer. Clean the repair area with soap and water, followed by wax and grease remover. Sand the repair and surrounding area and reclean with wax and grease remover. Protect adjoining panels, glass, or moldings with masking. Not as much masking is required, since the product is applied with an aerosol can. Final wipe the repair area to be sprayed with a tack rag.
This is where the real differences start (see Video). The primer-surfacer settles inside the aerosol can and must be shaken for about two minutes. Then apply the material in four or five quick applications without allowing the product to flash. This applies about 5–6 mils on horizontal surfaces, and slightly less than that on vertical surfaces. If thicker coatings are required, partially cure the material and apply a second series of coatings. This material has very poor hiding, It’s almost clear. So do not apply too heavily trying to achieve full hiding. Position the UV lamp 200–250 mm (8–10") from the surface and cure for two minutes. While the primer is curing, invert the aerosol can and spray until the spray tip and pick-up tube is emptied. During the curing process an iridescent glow will be visible in the primer. This indicates that UV curing is taking place. Oxygen can't be prevented from exposure to the top surface of the primer-surfacer and curing will not take place on this minute top layer. Use the recommended cleaner to wipe off this uncured layer. Sanding this uncured material will clog the abrasive disc. From this point on, all procedures follow the normal process. Guide coats can be applied. The repair area is sanded like any other primer-surfacer. After proper cleaning and additional masking, topcoats can be applied. Conclusion Repair facilities and refinish technicians now have another tool in the repair process. UV-cured primer-surfacer will provide benefits for many shops through increasing productivity and maintaining high quality repairs.
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