CARBONIZATION OF 3.5-DIMETHYL PHENOL-FORMALDEHYDE RESIN AND ITS CHEMICAL-STRUCTURE AT MESOPHASE APPEARANCE

The evolving gases during heat treatment of 3.5-dimethyl phenol-formaldehyde resin up to 1000°C were continuously analysed by means of gaschromatography, and the resin's structural change was investigated by using IR spectra. At 430°C, a mosaic type mesophase suddenly appeared over the whole sample. Most of the sample carbonized at 400°C could be dissolved in pyridine, its chemical structure having been analysed by using NMR. Only 5.5 mol/MW of H2O and 1.5 mol/MW of CH4 were evolved in the range of carbonization temperature up to 400°C, and the chemical structure at 400°C was nearly the same as that of original resin except for the formation of some methin and ether linkages with naphthene and heterocyclic rings; large aromatic condensed polycyclic structures have not developed yet at this point. At temperatures from 400 to 430°C, only 0.52 mol/MW of H2O, 0.55 mol/MW of CH4 and 0.02 mol/MW of H2 evolved, showing that no severe structural change takes place. Thus, the mesophase formation in this resin does not necessitate the pre-existence of large aromatic polycyclic structures, but is formed rather from planar large molecules. © 1979.