The acrylic moldings made by us tend to turn yellow after exposure to gamma rays. We are using a food grade approved acrylic for the housings.

Dear,

I advice you to do a search under article with the keyword "gammasterilization" on the devicelink website: www.devicelink.com. You will find a lot of very interesting articles on the effects of gammaradiation on polymers. One of them: Polymer materials selection for radiation sterilized products by Karl J. Hemmerich will certainly interest you (www.devicelink.com/mddi/archive/00/02/006.html).

Good luck,
Wim Renders

You can also get a lot of information in the book:
"Effect of sterilization metods on plastic and elastometers", by William Andrew. ordering information at: http://www.knovel.com/knovel2/Toc.jsp?BookID=378

and this is from an article written by W. A. Whitaker:

Acceptable sterilization technologies for acrylic are E-beam or gamma irradiation or dry ethylene oxide gas. While gamma sterilization has a tendency to discolor (yellow) most acrylics, this yellowing is temporary and recovery can be complete, with the parts retaining their original integrity. The higher the radiation dosage, the greater the yellowing and the longer the required recovery time. Until recently, when rapid-gamma-recovery formulations were introduced, acrylic took as long as 60 days to recover from the effects of gamma irradiation. This time has been cut to a week for some grades of acrylic.

Yaffa Raz