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So, I am exploring the idea of carbon nanotubes being used as an alternative to plastics in this sci-if universe of mine. They are flexible yet strong, while being biodegradable and nontoxic and so not damaging to the environment.

The main problem for substituting plastics with these is that, while most plastics are not electrically conductive, nanotubes are, meaning that their usefulness for, say, coating electrical wires is somewhat limited.

Is there a way to manufacture a carbon nanotube-based material that does not conduct electricity?

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It's a question of geometry.

Carbon nanotubes are conductive along their length, insulating sideways.

So the macroscopic object made of nanotubes just has to have them non-aligned, some sideways, and conduction will be blocked across the object.

See Turning Carbon Nanotubes from Exceptional Heat Conductors into Insulators, in which the authors "show that the κ [thermal conductivity] of a packed bed of three-dimensional random networks of single and multiwall CNTs is smaller than that of thermally insulating amorphous polymers." That paper is focused on thermal conductivity, but I believe the same applies to electrical.

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Short answer no.

A single pure carbon nanotubes will either be a conductor or semi-conductor depending on the orientation of the lattice. that is looking down the length of the tube it is possible to have different rotations of the hexagonal arrangement.

However in the bulk tangled clump form the conductivity is orders of magnitudes less then ideal.which would be more likely to occur in plastics.

If nanotubes are dopeds they can be turned into p and n type semiconductors which implies that if they are biased correctly they will be non-conductive, but that is not suitable for non-electronic bulk produced items.

There may be other impurities that can be added, but structure properties will likely be significantly altered and certainly won't be pure carbon nanotubes.

Maybe yes if all tubes in semiconducting orientation?

If the manufacturing process can be tuned to produce semiconducting oriented latice nanotubes. Then those were then non oriented in the products (think clump of tangled wires) they were in then perhaps they will be generally non-cunducting.

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A "carbon nanotube based material, probably.

Carbon can readily attach to other elements. I am not a chemist, but I'd suggest forming your carbon nanotube and then adding another atomic layer that insulates it. The carbon nanotube at the center may be conductive, but the resulting "wire" will have a coat of non-conductive insulation.

That might be an idea worth exploring.

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  • $\begingroup$ Coating carbon nanotubes to insulate them wouldn't really work. The whole process would be really expensive, wouldn't work all that well (because of quantum effect that would be in play if you coat them with one atom thick layer), and would probably result in a material that is not environment friendly. $\endgroup$
    – Negdo
    Feb 9, 2023 at 15:08
  • $\begingroup$ @Negdo Well, more than one atom thick. Something would work, it shouldn't take that many layers. $\endgroup$
    – Amadeus
    Feb 9, 2023 at 18:00
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Sadly, probably not. Wokopa mentioned using different geometry, but that would result in losing the other properties you want from this material (flexibility and strength). If that would even solve your conductivity issues on extremely small scales. And introducing other elements into the structure would just increase toxicity - and most likely not solve your problem.

Also, your asumptions on toxicity and degradability is debatable . In vitro we can degrade carbon nanotubes quite well, but in vivo it's another story. It is higly unlikely that carbon nanotubes aren't a health and environmental hazard. Long term studies are decades away, but I wouldn't be surprised if inhalation of dust would lead to similar symptoms as doing so with asbestos.

Instead, you can use halogen-free plastic for your wire insulation. It is not as big of an issue for the environment - burning it produce only CO2 and H2O, and it would serve the purpose. You can still use carbon nanotubes for other stuff, where their physical properties make them usable. Another good material to use would be the good old cellulose (well, not for wire insulation, but for other stuff)! Especially if you figure out how to (cheaply) make it artificially. There is no need to use plastic or carbon nanotubes to make furniture if you can use wood.

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