Cure In Seconds With UV/VIS Light

There are many ways that organic adhesives can be cured to their final, fully polymerized state. Two part epoxies just need to be mixed and they will react in minutes or hours at room temperature, depending on how they were formulated. Cyanoacrylates (“Super Glue”) polymerize rapidly on exposure to moisture in the air. One part epoxies cure when heated, typically in the 100° - 150°C range. And then there are the materials that cure when exposed to light, either ultraviolet (UV) or visible (VIS). An important class is the acrylate urethane chemistry that cures in a free radical addition polymerization. Once the reaction is initiated, polymerization occurs very quickly, within seconds. In order to trigger the reaction, a small amount of photoinitiator is included in the adhesive and it decomposes when exposed to UV/VIS light, creating the free radical. A second important class is the UV/VIS activated, cationic-cured epoxy, which also cures very quickly.

UV/VIS cure materials are most commonly used as encapsulants or coatings, where one surface is available for exposure to the light. The major advantage of UV/VIS cure materials is the rapid reaction, enabling complete assembly in just a few seconds. They are also used as adhesives for bonding clear materials such as glass or plastics. But even with opaque materials, modified UV/VIS adhesives can be used to advantage. For example, when bonding a mostly clear material there may be shadowed areas where light cannot be directly transmitted. In these cases, there are products available with secondary cures activated by heat or moisture. These two-step adhesives allow fast tacking of two components with UV/VIS cure and complete bonding through the entire structure with the secondary cure. Another approach for opaque materials is using a delayed cure UV/VIS epoxy. In this case, exposure to light triggers a “fuse” which allows a time delay for final assembly after which full cure is achieved. This “fuse” can be set for just a few seconds in a high speed, automated assembly operation.

While fast cure is the primary advantage of UV/VIS adhesives, long work life in a one-component product is a close second. As long as there is no exposure to the activation wavelength, these materials can be stored, dispensed, and assembled at room temperature for long periods of time.

Resin Designs specializes in producing custom formulations to meet specific application needs. While some representative products can be found listed
here, it is best to contact us and discuss the details of your project.
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