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Working on polystyrene & graphite composite, interesting effect(s)

  1. Nov 27, 2007 #1
    Dear Folks:

    I have been experimenting with composite conductor materials for a while, but have had little success with getting conductivity below 200 ohms/cm.

    Polystyrene gel is easy to make and offers recycling opportunities, so I have been using this as a starter binder.

    Found that if graphite powder is in a suspension with acetone and then 'reacted' with polystyrene gel in acetone, the gel will absorb the graphite from suspension till an approximate proportion of .725gr graphite:1.0gr weighted styrofoam raw. Very little graphite remains in the acetone suspension.

    From this attempted to see if the polystyrene/graphite composite was stable. I obtained a high speed blender with distilled water and wiped the composite gel at high speed as I poured it in. The graphite did not separate out into the water, but the composite broke up into small flakes. These flakes have low conductivity, so still stuck. After drying the flakes, reexposed them to acetone, they took a while to re-gel but did return to near original mass/gel.

    Questions:

    a) what is the underlying 'chemistry' affecting the absorbtion of graphite?
    b) any suggestions to improve conductivity?
    c) would exfoliation of the graphite help?
    d) would other solvent system help?
    e) open to suggestions.

    Graphite & polystyrene gel composites are mentioned in the literature, but no mention of this proportion.

    A similar reaction takes place with a graphite/manganese dioxide acetone suspension, but the polystyrene seems to cross link becoming stringy and stiff, but has my best low conductivity. This has toxicity issues.

    James




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  2. jcsd
  3. Nov 27, 2007 #2

    chemisttree

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    The aromatic groups of the polystyrene have an affinity for the planar extended 'aromatic' sheets of graphite. That could explain the affinity of the graphite to the PS. Conductivity in graphite requires the charge carrier to hop from one extended sheet of graphite to another. PS is coating the surface, however, and will block that from happening by keeping the sheets too far away from each other. A binder level over 50% with an insulating polymer (PS in this case) is not likely to conduct electricity extremely well. You would be better served to use a soluble conducting polymer such as sulfonated polyphenylene-vinylidine to preform your part. Thermal processing will remove the sulfur trioxide, resulting in a composite of graphite/polyphenylene-viylidine which, once formed, will resist further processing (it won't redissolve).

    What is 'exfoliation of the graphite'?
     
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