Micron polymeric precursors

Figure 10.2 Molecular structures of polymeric precursors for micron-size carbon fibers.

Ultra thin microporous carbon films are derived via the pyrolysis of phenolic precursors. The latter can be prepared from resorcinol-formaldehyde resins using a base catalyst. After several hours at 50°C of curing, the solution forms a stable polymeric film. Followed by a solvent exchange and ambient pressure drying, the film is pyrolysed in argon atmosphere at temperatures above 800°C. The result is an electrically conducting polymeric carbon film, the structure of which resembles the organic precursor, but shows microporosity in addition. Hereby, films with thicknesses of > 5 microns and sufficient mechanical stability can be made. 

A typical process for the production of vitreous-carbon spheres is represented schematicctlly in Fig. 6.9.1 The precursor is a partially polymerized polymer such as furfuryl alcohol, catalyzed with p-toiuene sulfonic acid and mixed with acetone to obtain the proper viscosity for atomization.l l A pore former is added which can be an organic material with a high boiling point or sub-micron solid particles such as carbon black. Atomization occurs in the thermal reactor shown schematically in Fig. 6.10.1 The curing time is very brief because of the small size of the particles ( 45jum). 

---