Thursday, July 14, 2011

Story of CR-39!

The abbreviation stands for “Columbia Resin #39,” because it was the 39th formula of a thermosetting plastic developed by the Columbia Resins project in 1940.
CR-39, or Allyl Diglycol Carbonate (ADC), is a plastic polymer commonly used in the manufacture of eyeglass lenses.
The first commercial use of CR-39 monomer was to help create glass-reinforced plastic fuel tanks for the B-17 bomber aircraft in World War II, reducing weight and increasing range of the bomber. After the War, the Armorlite Lens Company in California is credited with manufacturing the first CR-39 eyeglass lenses in 1947. CR-39 plastic has an index of refraction of 1.498 and an Abbe number of 58. CR-39 is now a trademarked product of PPG Industries.
An alternative use includes a purified version that is used to measure neutron radiation, a type of ionizing radiation, in neutron dosimetry.
CR-39 should not be confused with polycarbonate, a tough homopolymer usually made from bis-phenol A.

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 of solvents and other chemicals, to gamma radiation, to 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 in 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.
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
 
PROPERTIES
GLASS
PC
PMMA
CR39
Superior optical quality        
YES
NO
NO
YES
Lightness and strength          
NO
YES
YES
YES
Scratch resistant               
YES
NO
NO
YES
Stress cracking resistant       
NO
NO
NO
YES
Solvents and chemical resistant 
YES
NO
NO
YES
Welding sparks resistant        
NO
YES
NO
YES
Plasticizer migration resistant 
YES
NO
NO
YES
Ageing resistant                
YES
NO
NO
YES
Gamma radiation resistant       
YES
NO
NO
YES
Wide range of color              
NO
YES
YES
YES
Wide range of U. V. absorption  
NO
YES
NO
YES
PC: Aromatic Polycarbonate
PMMA: Polymethyl methacrylate

The CR39 plastic :

·         are colorless and completely transparent to the visible light and almost completely opaque in infrared and ultraviolet region of the spectrum. For these reasons, it is largely used for the production of sun glass lenses. They can be colored by surface dyeing or bulk tinting;

·         have high abrasion resistance and high-quality optical properties;

·         weigh about half as much as glass;

·         keep their excellent optical properties despite long-term exposure to chemicals like solvents, highly oxidizing acids, and strong basis;

·         resist to heat distortion up to 100 ° C and are resistant to small hot flying particles such as welding sparks.

Optical PropertyValue
Refractive Index1.498
Abbe value59.3
Density1.31 g/cm³

|| stand up to scratches, heat and household chemicals || have less chromatic aberration than polycarbonate lenses || are lightweight and less prone to shattering than glass ||

5 comments:

  1. Excuse me, is this article from wiki?

    ReplyDelete
  2. @Anonymous

    Yes, most of the portions are from wiki and i have quoted from some from other sites like http://www.df.unibo.it/macro/intercast/charact.htm,...

    ReplyDelete
  3. Does anybody know what the production capacity of CR-39 is ? Which company produces
    CR-39 ?
    If anybodu have any answer, please mail to sammy80@seed.net.tw

    ReplyDelete
  4. It's more than borrowed. It's a complete rip-off. Not cool Mahesh!

    ReplyDelete

Please write your comments here...