Carbomorph

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Contents

Goal

Replicate the results from http://www.plosone.org/article/info:doi/10.1371/journal.pone.0049365

Participants

Method

We mixed vigorously in a 250ml beaker for around an hour. Taking care to break apart the lumps of Polymorph that coalesced. This gave a thick dark pearlescent goo, with the Polymorph fully dissolved, and a lot of the DCM having evaporated off.

We then dried the goo on a ceramic plate, first in sunlight, then on a 40°C hotbed (patience is not a virtue). At this stage pattens where clearly visible in the suspended carbon. Whilst damp the goo was extremely sticky, but once dry easily pealed from the plate.

We then submerged the resulting plastic in n 80°C water-bath. We then dried it, and rolled it between two glass plates to form around 50cm of 3mm filament (with some wastage).

The resulting filament has a uniform appearance similar to pencil lead, but a rubbery feel and is more flexible then PLA (i.e. very similar to pure Polymorph). The filament fed into a TVRRUG Round 1 printer with Bowden conversion. Printing was possible above about 175°C, but with a high tenancy to block the nozzle. Heating to around 205°C seemed sufficient to clear the blockages. Further test printing necessary (we probably didn't wait long enough for it to dry).

The resulting plastic is none conductive. Even thin films (translucent, probably around the thickness of the carbon grain size) are sufficient to block any reading on a 40 M ohm meter.

We tried additional working of the plastic, and pre and post printing. Along with using a carbon based conductive ink to ensure good electrode contact.

Different graphite

We then tried a different type of 'Graphite powder' which appeared finer and blacker. This produced more promising results and at >40% carbon produced suitably conductive samples which still looked black and consitent and felt 'plastic'. However even below the threshold of conductivity they blocked the print head after a couple of mm of extrusion.

Nano tubes

Richard and I created some 15%wt carbomorph using carbon nano-tubes (got to love ebay) at Reading hackspace last night. 4g produced ~50cm of filament which was jet black and harder to work, but maintained a very 'plastic' feel and flexibility. The 3mm filament was hard to accurately measure but was below 100Ω/cm, a hair-width single extrusion was easier to measure at 1kΩ/cm.

However I have not been able to print with it. I believe this is due to its high thermal conductivity, possible coupled with softening at a low temperature. Starting an extrusion into a hot nozzle initially produces some extrusion, however seconds later extrusion stops and will not restart. I have manually tweaked extremely high extrusion pressures and run the temperature from 150° to 220° with no luck. (Getting to 220° is much harder then with PLA, and the carbomorph is soft all along the PEEK.). I also tried undersized filament, and just using 2cm in the hot-end with PLA as a plunger.

TODO

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