Comparative study of carbon dioxide and nitrogen atmospheric effects on the chemical structure changes during pyrolysis of phenol-formaldehyde spheres

The effect of CO2 atmosphere on the chemical structure changes of resol-type phenol-formaldehyde spheres during pyrolysis was investigated, in comparison with that of N-2 atmosphere, using FT-IR, TGA, and elemental analysis techniques. It was found that, in contrast to the expectation that CO2 may act as an oxidizing agent at high temperature, it behaves very similar to N-2 during pyrolysis of PF spheres up to 700 degreesC, but results in a somewhat different extent of some specific reactions. That is, although the reactions occurring up to 700 degreesC were dominated by crosslinking and/or polyaromatization under both CO2 and N-2 atmospheres, fewer alkyl-phenolic ether bonds were formed under CO2 than under N-2. As a consequence, the samples carbonized under CO2 at 700 degreesC were found to have more pendant groups on the edge carbon atoms of carbon in the carbonized samples than those prepared under N2 atmosphere. (C) 2004 Elsevier Inc. All rights reserved.