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Ultraviolet activated substances

  1. Dec 6, 2016 #1
    I recently purchased a bonding agent that is activated by an ultraviolet light (provided as part of the package). After three seconds of exposure to the UV light, the liquid substance turns rock hard. I believe they use the same process with modern dental fillings. Can anyone explain what is the physics/chemistry involved in this reaction.
     
  2. jcsd
  3. Dec 6, 2016 #2

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  4. Dec 7, 2016 #3
    Thanks. I was looking for the actual mechanism whereby the UV light induces the polymerization.
     
  5. Dec 7, 2016 #4
    The UV light creates a free radical. Then the monomers polymerize via free radical polymerization.
     
  6. Dec 7, 2016 #5
    So why UV light? Is this strictly because it is short wavelength/high energy. In which case, would x-rays work?
     
  7. Dec 7, 2016 #6
    No, the frequencies of X-rays are too high. The freqeuncy of the incident radiation has to be resonant with the electrons in the bond.
     
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