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Thread: An Experement

  1. #11

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    Ron,
    couldn't be PVOH hardenable (at least in an alkaline medium) by using boric acid? Or perhaps using glutaraldehyde?
    regarding its mechanical/optical properties, does it differ much from gelatine? were there any attempts for using PVOH in photo emulsions?
    since there are also some PVA variants available functionalized with anionic (and cationic) groups, couldn't be that stuff hardenable by just adding an aluminium salt?
    thanks

  2. #12
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    It is more common to use Acryl Amide, Poly Vinyl Pyrrolidone or Butvar in emulsions, and none of these nor Poly Vinly Alcohol resemble gelatin in any way. Gelatin has a structure which is imposed by its protein makeup. The amino acids act to peptize gelatin and it can chill set and crosslink. The others can, but under conditions often harmful to the silver halide grains.

    The Silanes probably add something to the mix to improve the activity of the vehicle with the AgX crystals. IDK. It also may supply hardening sites. We usually used a site with an active methylene on it so that we could harden.

    I've worked extensively with polymers in order to replace gelatin. It is not an easy task. I await Bill's results.

    PE

  3. #13

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    Ron, what do you mean with a site with an active methylene-on which polymer? gelatine?
    so PVP could be a "lousy" substitute for gelatin?
    I am also very curious about Bill's results!
    thanks

  4. #14
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    Gelatin has active cross linking sites that work with formalin or other hardeners. These are amine based. Other active sites which can be placed on polymers are -C=O CH2 C=O (this is hard to draw and explain). In any event, Poly Vinyl Alcohol by itself is difficult to harden and has no sites to peptize Silver Halide grains as they form.

    Therefore, something else (Silane?) is helping Bill. I am curious as well.

    PE

  5. #15

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    Quote Originally Posted by Photo Engineer View Post
    It is more common to use Acryl Amide, Poly Vinyl Pyrrolidone or Butvar in emulsions,
    Butt-Head: Whoa, huh huh, he just said "Butvar!"
    Beavis: Yeah, Heh heh heh eh eh eh heh heh heh.

    Sorry...
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

  6. #16

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    Silanizing agents attack compounds that contain hydroxyl groups by displacing the alkoxy groups on the silanizing agent and forming a covalent -Si-O-Si- bond.

    It seems to me reacting a silanizing agent with Polyvinyl Alcohol will just add the silane to the alcohol groups - it will add mass to the PVOH chain, but not crosslink anything.

    Also, to those reading that don't have experience with silanizing agents, they are kind of nasty compounds. You need to take real care when handling them. They are toxic through contact with skin and corrosive - that is they react with your skin as well.
    Last edited by Kirk Keyes; 06-23-2011 at 12:20 AM. Click to view previous post history.
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

  7. #17

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    Kirk, actually we don't know how the PVA (in this case) is derivatized, crosslinked or not. The Kuraray site states that it has silanol groups. therefore, these are probably more or less Si-OH groups which can interact with glass surface by hydrogen bonding SiOH......HOSi and of course within the polymer itself
    I have first-hand experience with silylating (mostly trimethylsilylating to be precise) agents, since we use them in our lab for GC work. They are really useful stuff (greatly extend the volatility range of coumpounds), but yes, they are really nasty to work with.

  8. #18

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    Quote Originally Posted by T-grain View Post
    Kirk, actually we don't know how the PVA (in this case) is derivatized, crosslinked or not. The Kuraray site states that it has silanol groups. therefore, these are probably more or less Si-OH groups which can interact with glass surface by hydrogen bonding SiOH......HOSi and of course within the polymer itself
    I have first-hand experience with silylating (mostly trimethylsilylating to be precise) agents, since we use them in our lab for GC work. They are really useful stuff (greatly extend the volatility range of coumpounds), but yes, they are really nasty to work with.
    It's been made probably along these Kuraray's patents: US 4617239 and US 4567221.

  9. #19

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    Quote Originally Posted by T-grain View Post
    I have first-hand experience with silylating (mostly trimethylsilylating to be precise) agents, since we use them in our lab for GC work.
    Same here.

    What GC stuff do you do? I run air for volatiles with GC/MS (TO-15) and various drinking water and waz waste methods for water and soil with ECD or FID detectors.
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

  10. #20

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    Quote Originally Posted by Kirk Keyes View Post
    Same here.

    What GC stuff do you do? I run air for volatiles with GC/MS (TO-15) and various drinking water and waz waste methods for water and soil with ECD or FID detectors.
    As for silylation, we do mostly aminoacids and other similar stuff (cannot disclose everything, sorry ). Otherwise, we do mostly food and pharma analyses, a wide array.

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