Saturday, July 07, 2007
I'm gettin' places!
Okay, today has been an excellent day, and not just because it was so fine to go down to the beach riding my motorcycle.
Today I opened the boxes that arrived this week, with new products for me to go *Frankenstein* with my resins (meet my resin bottles to the right).
1st box: N-methyldiethanolamine, the stuff that stops oxygen scavenging in it's tracks.
Remember how that effect was slowing down the setting and hardening of my resins, specially for polyesters? If not, you can read about it on the post below. Well adding a little N-methyldiethanolamine has reduced the curing and hardening time from something around 40 minutes to.... UNDER 5 minutes!
Here is my big rig with the stronger fluorescent tubes, the one that's on here is the germicidal UV one.
With this setup I will nos start fine tuning the mixes so as to get something that will work perfectly well in a syringe and will be fast curing!
It's really close now! Really, this thing hardened so fast that I literally didn't see it happen. In fact it was so fast that it wrinkled the surface of the resin because it hardened before the inside got time to do so.
Just a minor problem that will be tackled in my next experiments.
2nd box: Titanium Oxide powder, a common white pigment that should act as both a filler and a co-initiator, improving depth cure. Well that hasn't worked so well. It has such a diffusion power that the UV radiation gets swamped before it can make its effect. This pigment has some serious covering properties. I will need to use a lot less to see the desired effects. To be continued...
3rd box: Copper powder. This one is straight forward: I wanted to fill my air-drying acrylic i bought the other day with a fat load of copper powder to see if i could get a conducting thread.
On this picture yous see a number of threads i spread over a Polystyrene board with my copper filled acrylic resin, after 1 hour drying. The shiny part that looks like copper I achieved by polishing the hardened thread a little, with a rounded metal object. Isn't that just the most amazingly unexpected thing? I was not hoping this good a result! And I didn't even load the resin to the maximum ability! It's loaded with about 50 volume % copper, i could probably go up to 70v%! And you know what? you could probably use any regular glue to get this stuff, it's so damn easy I tell you!
Now, not everything is perfect. The threads still have a quite high resistance.
Here I made a measure of the polished track's resistance. those are 10 kOhms by the way... And the non polished, quite porous thread has a resistance through the roof! :$ Anyway, the thread varies in resistance and sometimes it's a lot lower. This thing needs to be copper plated still, and that should get us where we want. By the way, the thread sticks pretty nicely on the board, but maybe using strong glues (epoxy?) would give us a better result, specially at very high copper loads.
Anyway, I'm very happy with my results today, I feel like I made a big leap! Cheers to you all RepRappers, and thanx for all your ideas and inspiration! I'll have some drinks on us all to celebrate this :)
Afterward, you could copper plate it if you needed lower resistance.
You might be able to recycle some old laser printer guts to disperse the powder.
I believe something very similar to this method is used to electroplate non-conductive objects (like tree leaves).
Man, idon't have a reprap machine, because if I had, I would be printing circuit boards right now!
Once we get to the point that I can build a coreblower I am intending to create vented cavities and experiment with air-fluidized powders with extremely high filler loads (+99%) to take that idea to its extreme.
Mike: You have more knowledge than me on fillers, and I'm sure you are right with the extremely large loads of metal powder. the stuff i use is so fine that the bonus effect of being able to compress it and improve conductivity is really providential! I will try what you suggest and who knows, maybe we don't even will need to plate these threads. printing and compressing them would be enough to get a circuit board. I was also thinking about a heat system that would melt the grains together. Aluminum would be the metal of choice then as copper has a way to high melting temp. keep me in the loop with the test you make with that. With these three research lines I think we are very close to making conductive materials work, one way or the other.
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