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Old 3rd February 2005, 10:12 PM   #11
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The Quads do seem relatively well sealed, but certainly are not hermetic. But there are bound to be small leaks which will allow slow air exchange. During a long humid summer, the interior humidity has got to rise to match the ambient average level. And likewise fall in the winter. The Quads must use a coating which is fairly well behaved over humidity changes. The coatings I've seen are black, as in carbon bearing. I know that early Quads used dissolved nylon, but I'm not sure what the 63s used.
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Old 3rd February 2005, 10:31 PM   #12
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Quote:
The problem with those coatings is adhesion- without treating the film surface, getting them to stick permanently will be nearly impossible. In order to get really good adhesion to Mylar or Saran, you need to do something like corona or plasma treatment to get the surface energy up to 45 dyne or higher. It can also be done chemically, but it involves VERY nasty stuff like chromic acid.
I assume you're referring to the Sony patent. I'm no chemist, so I wonder if you can tell by looking at the ingredients if anything there would work to ensure (or preclude) a good bond. We certainly don't need a thick layer. The patent is encouraging in that it shows thoroughness by testing several parameters, so if adhesion were a problem, you'd think they would have caught it.

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Many of the chemicals mentioned in the Sony patent are reasonably dangerous... I didn't read it all yet, there may be a unique combo that is only moderately dangerous and perhaps suitable for DIYers...
My concern too. Hey, I don't even like solder flux vapor, and I use a suction system to draw that stuff out the window. I do see some chemicals in the Sony patent that I use already but I treat carefully, such as ferric chloride. Used outside in fresh air, perhaps with a ventilator, and some caution, I'm thinking of trying one of the easier and less toxic choices from the patent. The advantages touted in the patent are very tempting. Grinding graphite is no fun either, that's for sure!
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Old 8th February 2005, 01:37 AM   #13
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Default 1 week and counting

It has been a week with the HV bias on continuously and the stove-black diaphragm coating is still working fine.

I'll update again in a month or two...

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Old 8th February 2005, 02:15 AM   #14
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Quote:
I assume you're referring to the Sony patent. I'm no chemist, so I wonder if you can tell by looking at the ingredients if anything there would work to ensure (or preclude) a good bond. We certainly don't need a thick layer. The patent is encouraging in that it shows thoroughness by testing several parameters, so if adhesion were a problem, you'd think they would have caught it.
Actually, the patent is more of a shotgun, with essentially no data on adhesion or longevity. I was referring to coatings in general on Mylar or Saran.

There's really no good reason to use conductive polymers rather than filled polymers as coatings and quite a few good reasons not to: expense, stability to air and moisture, mechanical ruggedness, toxicity...
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Old 9th February 2005, 02:07 AM   #15
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Default That SONY patent...

I got a few minutes today to read the SONY patent...

It seems like this is a possibly do-able DIY "coating." It actually converts the surface of the poly chemically, so there is no "adhesion" issue.

There is some degree of danger using the least difficult of the chemicals. Two of the "oxidizers" are fairly easy to get - ferric chloride and ammonium persulfate are both commonly used to etch PCBs... so if you have experience with PCB etching, ur probably ok here...

The other part, the aniline I'm not so sure of... I know about aniline dyes, and I don't want them on or in me, but the dyes are sold for all sorts of things, including wood staining... dunno enough to determine the relationship between the quoted chemicals and the dyes. We would be lucky to have the dyes work here...

The process seems fairly straightforward bathe for a few hours then bake/dry. Rinse in hyper clean water. Done.

Any chemists out there who can identify the aniline compounds quoted??

Seems interesting...

Of course the stupid graphite method seems to work in many cases indefinitely and almost never less than 15-20 years done right and not soaked in humidity all the time...

If you live in southern FLA or Louisiana, the rainforest, this SONY method is clearly for you!

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Old 2nd March 2005, 12:38 AM   #16
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Default One month and counting

It has been a month since I installed the stove-black coated diaphragm and it is still working fine. The speaker has been powered up the entire time.

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Old 2nd March 2005, 12:52 AM   #17
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Bear, as it happens, I'm a coauthor on the first definitive paper on polyanilines (Synthetic Metals 121, 173 (1985)). And I've got a handful of patents on using the materials in electronics manufacture. They are potentially suitable (though not optimal) as coatings, but you can't make the diaphragm out of polyaniline, then dope it into conductivity- the films don't have great integrity. It's a gimmick and absolutely not suitable for diy.

Forgot- thanks for the update. let's see how long we get out of this...
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Old 4th March 2005, 03:52 PM   #18
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Originally posted by SY
Bear, as it happens, I'm a coauthor on the first definitive paper on polyanilines (Synthetic Metals 121, 173 (1985)). And I've got a handful of patents on using the materials in electronics manufacture. They are potentially suitable (though not optimal) as coatings, but you can't make the diaphragm out of polyaniline, then dope it into conductivity- the films don't have great integrity. It's a gimmick and absolutely not suitable for diy.

Forgot- thanks for the update. let's see how long we get out of this...
Man, I now feel entirely inadequate in all respects...

Heh.

Anyhow, I didn't quite follow your comment above... the SONY patent calls for using it as a coating layer on a poly film, not the film itself as I read it, no?

Are you saying the SONY method, or similar will not have "great integrity"??

And, what is the "polyaniline" part's basic chemical make up - any relationship to the aniline dyes??

signed,

.... still curious


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Old 4th March 2005, 05:15 PM   #19
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You just accidently picked door number 3!

Polyaniline is, as you might expect, a polymer of aniline, that is, a bunch of aniline sub units hooked up in a long chain. It exists in a variety of forms depending on the oxidation state and the degree to which the nitrogens in the chain are protonated (that was the basis of the paper I referenced). The perchlorate is an oxidizing agent, which in an acidic environment will cause the aniline monomers to chemically link up and form the polymer. That's the perchlorate's only role; generally, you wash it out of the polymer before doing anything else.

The polymer needs to be partially oxidized and then protonated (e.g., from an acid treatment) to become electrically conductive. In the unprotonated (free base) form, the polymer doesn't conduct but it can be dissolved and cast into a very cool-looking coppery film. That film then gets treated with an acid (protonating agent) to "dope" it. The conductivity varies enormously with humidity, and the polyaniline needs to be somehow amalgamated with another polymer in order to make a coating that won't flake off.

Polyanilines of various sorts were known as byproducts of the aniline dye industry, but the relationship between oxidation state, acidity, structure, and conductivity weren't really sorted out until the 1980s. I note that the principal author of this paper, Alan MacDiarmid, received the Nobel Prize in 2000 for his work in conductive polymers.

There. This is much more than you wanted to know!
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Old 4th March 2005, 05:43 PM   #20
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SY,

Good stuff! That really helps to explain the Sony patent.
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