Electrically conductive paint

[jwax]

Bigglez said,

What is that in "ohms per square" (the industry standard
for resistive coating measurements)?

At a width of 2 cm, and a length of 20 meters (2000 cm), there's a thousand squares.
Measures 2 ohms.
2/1000= 0.002 ohms/square. (@ 0.3 mm thickness)
Impressive!

[haklesup]

Sheet R= R/(L/W) 20m / 0.02m = 1000 squares , 2 ohms/1000 = 2mOhm/square = Sheet Resistance

rho=R(A/L) , rho=2(0.02*.003)/20 = 6uOhms*m = bulk resistivity (6E-6)

not sure how he got to the other unit Ohms/mm^2

In any case, its not a bad figure, the other consideration for paint would be durability. A topcoat of clear acrylic (or color paint) would passivate and protect most coatings. This puts it about 5-7 times less resistive than NiCr and 10x to 100x more resistive than most metals.

http://en.wikipedia.org/wiki/Resistivity

Looking at the chart in the link, I never realized how conductive calcium is. Well I don't see much elemental calcium anyway, most of it is locked up in calcium carbonate and other compounds or dissolved in water with other salts. Has anyone ever heard of an electrical component (or part of one) made of calcium?

[jwax]

Interesting!
http://www.encyclopedia.com/doc/1G1-95500871.html
(6 year old article)

[R&DA]

First, I want to thank all responders for the accolades. That's from the heart!!!

I just dubbed it "The ElCon Paint". From the Jwax entry I went to Wikipedia and found that ElCon's Resistivity is 20 x higher than Silver (metal), but 1/100 that of bulk Carbon. I agree that's interesting - to the point of trying to make a business product of this.

To Haklesup & Bigglez : thx for the calculation - I'll try to measure the "ohms per square" directly this week. As for Ca, this is a very reactive material, and is therefore both difficult to obtain, and difficult to work with. Considering its electrical properties, small wonder Nature uses it so much for life processes.

The first product I've in mind is electrically conductive flooring for the sport of Fencing. IF, that is, it can be made at competitive costs to what's out there.

Speaking of uses, any good ideas?

[R&DA]

Further to John:

The conductive medium of the ElCon composition is not copper, nor silver, nor carbon.
At present I've no data on max current density. Presumably that is a function of temperature, which in turn depends on whether there is an overcoat or insulation or air cooling etc. However, to get an idea, I'lll make some experiments this week. I'll keep you posted.
Curing temperature is room, air dry, nothing special. Just make and apply and go away for a day.

Harry (of R&DA)

[jwax]

Thanks Harry!
Harry said,

Speaking of uses, any good ideas?

Sure! Send any of us interested a sample!
That's market research at its finest!
We'll let you know all about it!

[R&DA]

Hi Jwax et al,

sample? sure. It will be of the flooring with the paint on it. Send me your physical address to [email protected] & I'll mail you an envelope with a sample immediately.

Same for any other interested person.

Caveat: at this time the pot life is too short to send out paint. I make it and use it immediately. So if someone wants me to apply it to something, I'd have to do it at my place.

Harry

[haklesup]

the pot life is too short to send out paint

Using a highly volitile solvent perhaps or is is a polymer reaction?

High VOC paints are out of favor in the industry now. Unless it is something reletively benign like an alcohol anthing else may need to ba applied in something like a paint booth as is required for auto painting. Even acetone would present significant regulatory issues in CA. I'm thinking a flooring application is a lot more material than a small electronic part or contact repair.

I'm just saying, if you plan to commercialize it, make sure to do your homework on the EPA and state laws first. This mainly may limit what you can sell to untrained customers but as a properly educated and trained contractor, this could make a decent job for you. Particularly if you are mixing and applying your propriatary coating yourself and/or by licensed franchises using appropriate techniques WRT enviornmental laws.

[R&DA]

Hi Haklesup,

the reason for short pot life is not any of the concerns you raised. Can't go into details, but safety is absolutely NOT a concern. If push comes to shove, I could sell the system as two parts, one liquid, the other solid, and have the customer mix and apply quickly. However that's hardly professional. So upon the wear test returning good answers, and some sales ensuing, I'll have a lab develop chemistry to enable long pot life, for paint sales. By long I mean even 3-4 weeks.

Meantime I'm also working on some other tacks to bypass the problem.

Thx for the advice. Keep it coming, please!

Right now I need to find some buyers of painted vinyl, for any purpose.

I'll be making some conductivity experiments shortly, using DC.

Harry

[Bob Scott]

Right now I need to find some buyers of painted vinyl, for any purpose.

There might be a market for this paint in electronic equipment factories to control ESD (electrostatic descharge). Paint the floor and furniture. ie: Anywhere employees are required to wear ESD wristbands.

Can this stuff be used instead of copper on circuit boards? I'm thinking of a simple silkscreen process. If I recall correctly, appliance manufacturers already use some type of conductive paint to make flexible PCBs for washer, dryer, stove etc. control panels.

[Bigglez]

Has anyone ever heard of an electrical component (or part of one) made of calcium?

A hollow Cathode Lamp(HCL).I may have a calcium
one, amongst several in my tube/valve museum.

[Bigglez]

Speaking of uses, any good ideas?

A 3D enclosure, with electrically conductive walls would also be known
as a "screen room". Necessary for some RF testing work,
calibration labs, and possible secret uses in black ops.
There are commercial companies that build these today.

If that enclosure was, say, a restaurant, the patrons
inside would not have cell phone access. As many
cell phone addicts can't keep off their phones or other
mobile devices they disrupt the dining experience
for others.

A cell phone free zone would have immediate popularity
(and commercial success), more so if the existing room
could be 'painted' to become RF free instead of major
renovation.

BTW, cell phones can be jammed. However, doing so is
both illegal and intrusive to other RF users or legitimate
users outside the kill zone.

[haklesup]

I think this may be too conductive for ESD protection and not conductive enough for most PCB conductor applications though low current apps like connecting an LCD would be acceptable. However, you would be surprised how much resistance some circuits can tolerate particularly if it is a known quantity, it may find a niche here.

As an EMI shielding coating it could be useful both at the small scale of mobile devices (I often see a painted surface inside enclosures to keep the noise in) and maybe at the larger scale of room shielding. You would need to characterize its sheilding properties over a range of frequencies to market it this way.

As a surface activator to electroplating plastic parts, maybe, but it may be too thick for this. Probably overkill as well (more conductive, more costly than necessary).

2 part mixes are not unusual or unprofessional IMO. From epoxy, to paint to patching compounds, plastics and concrete addmix, it happens all the time. Find a way to make the solid part liquid and it would be easier to handle and faster to mix two liquids

[R&DA]

Yea, thass' me.

Turns out the material is not as I'd hoped it be. On curing well, the resistance increase a d___ lot, and even then is not stable. As soon as I've finished the current spate of measurements (few days), I'll publish here my new figures. For now, the original fencing flooring market is out.

However, for easy ESD protection and Faraday cage creation and static dissipation, the material will probably work. So bearing that in mind, pls keep the ideas coming.

Restaurants and elx rooms and eavesdrop-safe rooms and concert halls and CLASSROOMS!!! (end of cellphone cheating!!) - good idea!!!!!

Thx,

Harry