UV absorbance in clear epoxy 3

[windell747]

Hi, I'm poting some UV LEDs in clear epoxy in which will be submerged in seawater. The UV LEDs will shine through the clear surface of the epoxy to prevent bacteria growth on the epoxy surface.

I would like to know the rate at which UV light is absorbed in the epoxy before it exits the epoxy. Resource suggestions would be greatly appreciated.

 

[IRstuff]

You need to get that information from the manufacturer of the epoxy. There are too many types of epoxies and characteristics to make any serious estimate. However, you should note that there are many epoxies that degrade with UV exposure:

http://www.loctite.com/int_henkel/l...elec_ComparPropertiesOpticallyClearEncaps.pdf

TTFN

 

[windell747]

Thanks IRstuff! Actually I ran across that technical paper a little while ago and I agree about the epoxy degradation. However, the paper doesn't seem to talk about the epoxy degrading due to UV exposure. It does talk about the yellowing due to thermal aging.

In the case of many epoxies existing, would you recommend a commercially available epoxy in which I could probably buy at a marine or hardware store in which doesn't attenuate UV light to a high extend and can uphold to UV radiation fairly well?

 

[IRstuff]

I would try to find an optical epoxy, since that's more likely to be formulated to both transparent and resistant to UV.

http://www.dogpile.com/info.dogpl/s...-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/417/top/-/-/-/1

There are a large number of UV resistant epoxies, suggesting that UV degradation is a real issue:

http://www.dogpile.com/info.dogpl/s...-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/417/top/-/-/-/1

You could certainly try some of these other epoxies, as they're probably cheaper than an optical epoxy.

TTFN

 

[unclesyd]

We used a lot of UV cured epoxies from these people. They supplied some specials that once cured were quite resistant to UV light. You might contact them to see what is available in epoxy or other materials for your application.

http://www.masterbond.com/wbarticles/wbuv.html

 

[windell747]

Thanks for the invaluable replies guys! It looks like there is a lot to select from!

 

[unclesyd]

Ran across this while looking for information on an entirely different subject. It looks like they have a very good selection on photonic materials.

http://www.nusil.com/Engineering-Silicones/photonics/index.aspx

 

[windell747]

Thanks for thinking of my thread although it has been a while since your last post! Much appreciated!

Windell

 

[Blazotron]

windell747,

You might also look at Epotek. I don't have a specific product in mind, but I have had good luck with their products in the past, and I am sure one of their tech people can suggest something.

http://www.epotek.com/

One other thought would be to figure out what type of polymer the company that makes your LED's uses to make the LED lens, as they by necessity would need to be UF resistant to the wavelengths of concern. It may not be an epoxy, but it might give you an idea of things that are likely to work. Just a thought.

Good luck.

 

[Anat0ly]

If you want I can measure its UV absorbance for you. I have access to a UV-Vis spectrometer in my lab. You would have to send me a sample of your material that is about 1 sq.cm. Thickness should be a few milimeters so that calculations can be performed accurately. Let me know if you are interested. Take care.

 

[windell747]

Hi Anat0ly, Thank you for your reply! Unfortunately, I've already potted the LED arrays in a epoxy that was provided as a sample by Epoxies.com. Since the size was a sample, I had to use all of the epoxy for potting the arrays with none left over to provide you with a sample. I really appreciate your offer and its unfortunate that I can't take you up on it. Maybe, if the opporitunity arises again, I'll remember to ask you! Thanks!