Knowledge on UV
Why UV Curing?
One part adhesives that cure using ultraviolet light provide an extremely convenient method of curing on demand, unlike two part adhesives that need to be mixed and used within a certain time frame. Not only is this more convenient for the user, it also eliminates many potential sources of process variability.
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. The most significant property of UV light is its intensity. The intensity of light, which can be measured by a radiometer, is designated by milli-watts per square centimeter (mW/cm²) or Watts per square centimeter (w/cm2). The key to UV curing is matching the wavelength range of the spectrum to a photoinitiator in an adhesive.
Every high performance adhesive has at least two components to it. An obvious example is the two-part, room temperature curing material already mentioned. A less obvious example would be contact cement, where only a single material is handled. For this kind of adhesive to work, a solvent must evaporate from the product, leaving the actual bonding resin behind. So, the resin is one part and the solvent is the second part.
In an ultraviolet-curing adhesive, there are also two components. One part is the adhesive itself and the second part is the photoinitiator which will not react with the resin by itself. The photoinitiator must absorb the ultraviolet light before curing takes place. When the UV light is delivered, the photoinitiator will undergo a chemical reaction and cause the adhesive to harden.
Why Use UV Adhesives?
• No two part mixing required
• Cure on demand
• Environmentally friendly
• Faster, stronger cures
• Minimizes adhesive shrinkage
• Decreases moisture absorption
• Increases humidity resistance
• Decreases out gassing
• Reduces defects while increasing yield
• Reduces cost