FAQ

Materials that cure using ultraviolet light provide an extremely convenient cure on demand capability. Other compounds that harden, for example, at room temperature must be mixed and used within a certain time to obtain the best results.

Typically there is no mixing required for UV-curing materials, nor is there any requirement to use dispensed material within a short time period. Not only is this more convenient for the user, it also eliminates two potential sources of process variability-meaning more consistent results!

We will look at what Ultraviolet light is, how it interacts with UV-curing materials and different types of UV-curing adhesives.

What is UV Light?

Ultraviolet light is a particular portion of the light spectrum, typically considered to be in the wavelength range from 200 nm (nanometers) to 400 nm. Light in this spectral range has many important uses including water purification, semiconductor lithography, UV ink and UV varnish "drying", sun tanning and, of course, adhesive curing.

Since ultraviolet light falls below the visible portion of the light spectrum, we cannot see pure UV light. This can be an important onsideration, because another significant property of light is its intensity. Special equipment -a radiometer- is required to measure the intensity of UV light. The intensity of light falling on a surface is measured in milliwatts per square centimeter (mW/cm2), or power (mW) per unit area (cm2).

UV-Curing Adhesives see under own chapter

UV Cure Conditions

Previous research has demonstrated that adjusting cure conditions can favorably impact the performance properties of many UV-curing adhesives. Critical applications may require a sequence of curing steps-involving different intensities of light and duration of exposure-in order to optimize results. Less sensitive applications will also benefit from ensuring that cure conditions are suitable and consistent from one period to the next.

Curing equipment should be engineered to ensure repeatability in critical UV parameters, such as intensity and duration of exposure. The ability to adjust the spectral profile of a UV light source can also be very important, as different adhesives may respond more favorably to different spectral inputs. Similarly, when working with a variety of bonding surfaces-notably plastics-changing the UV output profile can avoid excess heating of the surface.

Conclusion:

The use of ultraviolet light to cure adhesives brings many benefits to product manufacturers. Among these are ease of use, process consistency and flexibility, reduced environmental considerations and the availability of high performance materials.

When suitable material selections are made and understood, best practices for adhesive curing are implemented, and process monitoring and feedback are in place, the potential for consistent, high yield product assembly is significantly enhanced. One part of this is understanding the factors that affect process reliability and adhesive performance.