I don't understand much about the processes of graphitization/pyrolysis/ carbonisation. Hence the question. Is it possible to perform graphitization or carbonization on thermoplastic polymers such as PMMA/ PP/PS etc. For instance if I were to take a large cube or block of any of the above mentioned polymers and place it in a furnace, will it give me a good quality graphite cube at the end of the process? Will the melting of the polymers play a role in the process?
In principal you can do this, but generally this would be converting a high value material to a lower value material. If you want to be sure there are no impurities, you can start with essentially any hydrocarbon. Using a purified or special purpose hydrocarbon such as you mention is not necessary. The important part of the process is high heat for long time. Without some care, you are likely to end up with a highly disordered structure rather than crystalline graphite. The process of getting high-quality (highly crystallized) graphite depends more on process parameters than starting materials so long as the starting material is a typical hydrocarbon.
Yes, you can perform graphitization / carbonization reaction process on thermoplastic polymers. Actually the process should be called pyrolysis and has to be conduct in an inert environment such as nitrogen gas. The end product should be a char like material. Note that the pyrolysis process has to be conducted at a temperature below the melting temperature of the material that you are carbonizing.
Finally, the carbonization process is energy intensive like that used to convert the petroleum derived Poly Acrylonitrile (PAN) material into carbon fiber.
Hope this helps answer your question.
Professor Yehia Khalil, Yale University, USA
Fellow of the University of Oxford, United Kingdom
I must say that you plan to do is highly unrealistic.
1. Only very specific thermoplastics like PAN are graphitisable, due to their chemical structure and composition. The vast majority of the others have a quite low carbon yield, sometimes close to zero (PE, PMMA, for instance).
2. As they are thermoplastic, they'll melt so that the shape of the solid will be lost. A huge amount of gas will be produced, leading to porosity and sometimes top foams. The residue will be very light and extremely fragile. Nothing to do with a big, nice, carbon monolith.
3. Obtaining carbon, even not graphitised, requires high temperatures, 900°C is a very minimum, so you have no chance to do any carbonisation below the melting point !!!
4. Thermoplastics like PAN can be stabilised (i.e., for doing carbonisation without melting) by mild oxidation. This requires a high contact area with the oxididing as (air in general), so you can never avoid melting if you deal with a cube: only the faces will be oxidised at a depth of a few microns only.
Alain
Dear Sameer,
for me it is not absolutely clear why you want to do this and what should be the result. Perhaps you can add some more information in your question.
Nethertheless all three answers are correct but let me try to conclude it:
1. Every polymer containing carbon, hydrogen and other elements can be carbonized and show a carbon yield between 0,1% and maximum the content of carbon in the sum of the molecular weight.. Oxygen must be excluded in the atmosphere because it reduces the carbon content forming carbon oxides.
2. This carbonization will work with thermoplasts and thermosets. Thermoplasts will melt before the molecular structure will be converted. So the resulting carbon structure is worse and the carbon content is low. Thermosets are unmeltable and for that reason they can show a higher carbon yield and a better carbon structure.
3. Some thermoplast material like polyacrylonitrile (PAN) can be converted in a cyclized ladder-structure crosslinked before carbonization (stabilization process). This results in a higher carbon yield. The ladder structure helps to form graphit-like layers but that is no graphite (!). The interlayer distance between the layers is not small enough.
Perhaps I can add some more information for you, but please describe more in detail what kind of resulting carbon material you want to get. Please also describe how this material should be different to existing graphite material which is available on the market.
With best regards
Michael
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