Robert Lesko, president of HID Ultraviolet, Sparta, N.J., says the “instant” curing aspect of UV-curable resins has been used commercially to coat products in a manufacturing setting for years. The development of new equipment that enables portable “field curing” of UV-curable formulations has widened their application to the floor coating market. Here’s why you should think about UV-curing, acrylic-based resins.
Decorative concrete contractors are familiar with solvent- and water-based acrylic sealers. But those are very different from new-to-the-market, UV-curable coatings, which are a special type of acrylic with many properties:
- They cure in a fraction of a second.
- They resist almost all stains, acids, alkalines, and solvents.
- They have almost no VOCs or water added, so there is virtually no smell and no change in volume after curing.
- As a cross-linked product, they are perhaps the hardest, abrasive-resistant product on the market.
- The uncured acrylic allows UV radiation to pass through it before curing, but not after the resin hardens.
- They can be applied on surfaces below 0º F and can resist temperatures in excess of 200º F after curing.
- Floors can be restored to service in a very short time.
How to install
Charles Toth, commercial sales manager Americas for DSM, Elgin, Ill., says his company’s acrylic coating, Uvolve, must bond to open pores on concrete surfaces, so the surfaces must be opened up and laitance products removed. “Most contractors do this by diamond grinding, starting with 60-grit diamond pads and finishing at about 90-grit,” Toth says. “But you must be careful not to leave swirl marks or blemishes that will reflect through the UV curable coating.”
Because sunlight partly consists of UV light, applications work best indoors. Windows must be shaded to prevent problems. Toth suggests installing outdoors at night.
UV-cured acrylics can be applied by: rolling, spraying, or painting, with care taken to apply evenly. A typical application is about 5 millimeters, but thickness can be built up in layers as much as 30 millimeters, depending on the owner’s need. DSM’s product also can be colored for decorative purposes and can provide an antislip finish.
Once resin is applied, it remains in a liquid state until a UV light passes over it. Lesko says floor applications typically use a UV light-wand mounted on the front of a cart pushed by a worker. As the light passes over the uncured resin, it cures within a fraction of a second—well before the wheels of the cart could touch soft material. Product formulators specify the rate of travel for their UV light resins, typically ranging from 10 to 75 feet per minute. Handheld UV lights are available to cure smaller projects or hard-to-reach places.
We all know you should protect yourself in direct sunlight. UV lights for curing resins are even more intense than sunlight. Wear opaque clothing—a Tyvek-type suit is good because it blocks light and allows moisture to pass through. Workers shouldn’t have any exposed skin: hands, face, and eyes must be covered; face shields work well.
A final thought
UV-cured acrylics are good vapor retarders. If they bond properly to concrete, they will resist the forces generated by moisture vapor and provide good service. Contractors should be trained to install these finishes properly.