Thermal decomposition of methylene bridges and methyl groups at aromatic rings in phenol-formaldehyde polycondensates

Abstract

Phenol-formaldehyde polycondensates which contain methyl (or ethyl) substituents at different positions on the phenolic rings and methylene bridges at ortho or ortho and para positions were investigated. The products of pyrolysis at 600° C were analysed and the amounts of the alkylbenzenes and alkylphenols were related to the structure of the polycondensate pyrolysed. Most of the monoaromatic pyrolysis products are alkylphenols. The same alkyl substituents occur in the alkylphenolic pyrolysis products at the same positions that were present in the macromolecule. Methyl substituents were also found at the positions of the methylene bridges of the polycondensate, but their amounts in the pyrolysis products proved to be considerably lower than those of the methylene bridges related to the aromatic rings in the macromolecule. The amount of alkylbenzenes is only a few percent of that of alkylphenols in the 600°C pyrolysate, but the occurrence of the substituents in the alkylbenzene pyrolysis products reflects well the presence of the substituents and methylene bridges in the macromolecule.