FOR OPTICAL VIEWERS Applications CR-39 is transparent in the visible spectrum and is almost completely opaque in the ultraviolet range. It has high abrasion resistance, in fact the highest abrasion/scratch resistance of any uncoated optical plastic. CR-39 is about half the weight of glass with an index of refraction only slightly lower than that of crown glass, and its high Abbe number yields low chromatic aberration, altogether making it an advantageous material for eyeglasses and sunglasses. A wide range of colors can be achieved by dyeing of the surface or the bulk of the material. CR-39 is also resistant to most solvents and other chemicals, gamma radiation, aging, and to material fatigue. It can withstand the small hot sparks from welding, something glass cannot do. It can be used continuously in temperatures up to 100 °C and up to one hour at 130 °C. In the radiation detection application, raw CR-39 material is exposed to proton recoils caused by incident neutrons. The proton recoils cause ion tracks, which are enlarged by an etching process in a caustic solution of sodium hydroxide. The enlarged ion tracks are counted under a microscope (commonly 200x), and the number of ion tracks is proportional to the amount of incident neutron radiation.[4] In the 2008 paper "Nuclear tracks today: Strengths, weaknesses, challenges", nuclear physicist Saeed A. Durrani discussed the use of CR-39 as track detector.[5] In the same way, CR-39 is used as a solid-state nuclear track detector for autoradiography studies with alpha particles,[6] and for (comparatively cheap) detection of alpha-emitters like uranium[7] It is used in some photographic filters, such as the Cokin filter system. A direct equivalent is produced by Acomon AG with the brand name RAV, and another one by Danyang Yueda FineChemichal Co. Ltd in China. MUHAMMAD NAWAZ KAMBOH
Posted on: Sat, 08 Jun 2013 08:13:00 +0000
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