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Does anyone know how a photopolymer works chemically/molecularly? What is it about the UV light that makes it solidify?

sp332 14y ago
OK this literally is quantum physics and the discovery was Nobel-prize material but it's not that hard to grasp so here's how it works :) If you have a chemical reaction that requires a certain energy level, shining lots of light on it won't help much if each individual photon is below that energy level. Even if you have a really bright reddish light, each photon still only has a relatively low energy. On the other hand each UV photon has more energy than a red one, so they can add enough energy to cause a chemical reaction.
- tocomment 14y ago
  So it just needs energy to solidify? Would heat also work? So the molecules that it's made of up combine into new molecules that are solid? Do you know what the chemical reaction is?
  - sp332 14y ago
    Not sure about the exact chemistry but I think there are actually two exposures, one to harden the shape after which the unused material is removed, and then another higher one to make it less sticky or "detackify" it. Here's a paper from 1995 explaining the chemistry http://195.37.231.82/publications/pac/pdf/1995/pdf/6701x0025.pdf http://195.37.231.82/publications/pac/pdf/1995/pdf/6701x0025...
  - lepton 14y ago
    If "heat" is from a low-energy source, like an infrared lamp, then no it won't work. You need the individual photons to have enough energy.
  - ErikHuisman 14y ago
    Watch this movie for a brief introduction on quantum states. http://www.youtube.com/watch?v=kJBcXFsFa7Y http://www.youtube.com/watch?v=kJBcXFsFa7Y I've also googled around and found this picture explaining what is called uv curing. http://www.signindustry.com/flatbed_UV/articles/images/2008-11-UV_Ink_Reaction_to_.gif http://www.signindustry.com/flatbed_UV/articles/images/2008-... So basically the uv light is kicking the electrons up multiple levels in the "photoinitiators", the "photoinitiators" stabilize by dropping levels and giving off photons. These photons excite the "Monomers" and "Oligomers" between which electrons can freely flow (radicals) making it possible to form new bonds, creating longer chains of atoms (a polymer) /amateurexplenation

sp332 14y ago

OK this literally is quantum physics and the discovery was Nobel-prize material but it's not that hard to grasp so here's how it works :) If you have a chemical reaction that requires a certain energy level, shining lots of light on it won't help much if each individual photon is below that energy level. Even if you have a really bright reddish light, each photon still only has a relatively low energy. On the other hand each UV photon has more energy than a red one, so they can add enough energy to cause a chemical reaction.

tocomment 14y ago
So it just needs energy to solidify? Would heat also work? So the molecules that it's made of up combine into new molecules that are solid? Do you know what the chemical reaction is?
- sp332 14y ago
  Not sure about the exact chemistry but I think there are actually two exposures, one to harden the shape after which the unused material is removed, and then another higher one to make it less sticky or "detackify" it. Here's a paper from 1995 explaining the chemistry http://195.37.231.82/publications/pac/pdf/1995/pdf/6701x0025.pdf http://195.37.231.82/publications/pac/pdf/1995/pdf/6701x0025...
- lepton 14y ago
  If "heat" is from a low-energy source, like an infrared lamp, then no it won't work. You need the individual photons to have enough energy.
- ErikHuisman 14y ago
  Watch this movie for a brief introduction on quantum states. http://www.youtube.com/watch?v=kJBcXFsFa7Y http://www.youtube.com/watch?v=kJBcXFsFa7Y I've also googled around and found this picture explaining what is called uv curing. http://www.signindustry.com/flatbed_UV/articles/images/2008-11-UV_Ink_Reaction_to_.gif http://www.signindustry.com/flatbed_UV/articles/images/2008-... So basically the uv light is kicking the electrons up multiple levels in the "photoinitiators", the "photoinitiators" stabilize by dropping levels and giving off photons. These photons excite the "Monomers" and "Oligomers" between which electrons can freely flow (radicals) making it possible to form new bonds, creating longer chains of atoms (a polymer) /amateurexplenation