The week of March 18th I was privileged to attend RadTech’s Big Ideas Conference in Redondo Beach California. In addition to offering a nice reprieve from the Michigan winter, it also provided some keen insight into important things happening in the field of UV. So, for the next few pages, let’s take a look at how UV affects us in our everyday lives.
So, What is UV?
Let’s starting at the beginning. UV is short for Ultraviolet light. If you ever played with a prism when you were a kid, you know that light can be broken down into all the different colors of the rainbow. But this is only the visible portion of what scientists call the “electromagnetic spectrum”, shown in Figure 1.
As we can see, there are many other bands on both sides of visible light. These enable us to perform many of the daily tasks we take for granted, from powering our world (low frequency), to entertaining us (radio waves), to cooking our food (microwaves), and even diagnosing our illnesses (x-rays).
If we zoom in on visible light and its nearest neighbors, as we have done in Figure 2, we see that just above the visible band is infrared, which we use for heating and cooking, and just below it is UV – so named because it is literally a deeper purple than we can see.
What is UV Used For?
Nature has a purpose for just about everything! And, like the other bands of the spectrum, UV is both very powerful and very useful. You understand the “power side” if you’ve ever had a sunburn! You might notice that the UV band is sub-divided into UV-A, UV-B, and UV-C. According to the Mayo Clinic:
“Ultraviolet A (UVA) is the type of solar radiation most associated with skin aging (photoaging). Ultraviolet B (UVB) is associated with sunburn. Exposure to both types of radiation is associated with developing skin cancer. Sunlamps and tanning beds also produce UV light and can cause sunburn.”
This is the reason that your sunblock hypes its ability to block both UV-A and UV-B rays right on the label. But, in addition to the cautionary warning about UV exposure, this also points to some of the many uses of UV in the HBA (Health & Beauty-Aids) marketplace. Tanning and nail salons both use UV in the daily course of operating their businesses. The tanning part is obvious, but nail salons?
Modern nail salons use UV for curing the polish that they apply. Why? Two reasons:
- Reduced solvents – which means a lower odor, particularly from the acetone commonly used in off-the-shelf nail polishes
- Immediate cure – which means no need to sit around “stinking-up-the-joint” waiting for the polish to dry
And it turns out that this is a very important use for UV – the curing of coatings. I’m no chemist, so without getting into too much detail, it is possible to formulate coatings so that they cure immediately upon exposure to UV light. And by “immediately” I mean from less than a second to just a few seconds of exposure!
Since as I am writing this we are wrapping up “March Madness” a good example is the floor of a gymnasium. That glossy clearcoat is poured out and allowed to flow out evenly over the wood floor, then a UV curing machine – which, as shown in Figure 3, looks a little like a vacuum cleaner – is pushed over it. By the time the wheels (and the operator) reach the floor, the finish is cured hard enough to walk on!
Try that with your standard latex paint!
These advantages haven’t been lost on industry, either. Traditional finishes are cured by baking both to remove solvents and to cross-link the polymers that form the coating. This is fine for metal parts, but it can be a problem if your substrate cannot survive the baking process. Pre-finished wood flooring utilizes UV coatings to provide a hard, durable, attractive finish, without the warping and cracking that can accompany the baking process.
And wood is not the only modern industrial substrate that could be damaged in traditional coating operations. Plastics, composites, and a host of other materials can be quickly and easily coated and cured via UV methods – and, as with the gym floor example above, processed faster than with conventional coating methods.
Another good example is printing. Plastic labels and packages can be quickly printed with UV cured inks where a conventional solvent-based ink might actually damage the substrate while the two are in contact prior to the curing process.
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