Modelling of resole type phenol formaldehyde polymerization

Abstract

The kinetics of polymerization of phenol formaldehyde has been modelled to account for the formation of highly-branched resole molecules. The conversions of phenol and formaldehyde, number-average chain length, degree of branching and the concentrations of internal and external ortho and para-H atoms are obtained as functions of time, for several values of the various rate constants and the initial phenol to formaldehyde ratios. The conversions of phenol and formaldehyde are found to be most sensitive to the rate constant associated with the reaction between the external para-H atom with ---CH₂OH groups. The condensation between two ---CH₂OH groups prevents complete depletion of formaldehyde and leads to highly-branched, high molecular weight final products at large reaction times. Our studies show that at low values of the initial phenol to formaldehyde ratio, small amounts of lightly-branched, low molecular weight polymer with a high degree of substitution by ---CH₂OH groups is obtained. At some intermediate initial phenol to formaldehyde ratio, highly-branched, high molecular weight product is obtained and at high values of this feed ratio, larger amounts of lightly-branched, lower average molecular-weight product is obtained.