Study on the gelation rate of [formula omitted] solutions

Abstract

The gelation rate of atactic polystyrene in the solvent carbon disulphide has been studied. The time required to form a gel (gelation time) was measured as a function of gelation temperature, polymer concentration and molecular weight. A master curve was found for the gelation time-gelation temperature curves at various polymer concentrations by shifting the curves along the temperature axis. This means that a simple reduction between concentration and gelation temperature is possible for the rate of gelation, independently of the molecular weight of the polymer. It was also found that the temperature shift is attributable to the difference in the gel melting temperatures at different polymer concentrations, The critical gelation temperature was found to be ≈13°C lower than the gel melting temperature at a given polymer concentration. These results indicate that gelation in this system is a first-order transition and signify that the dependence of gelation rate on polymer concentration and molecular weight is related to their effects on the gel melting temperature T g m. The apparent activation energy of gelation at temperature T was found to be proportional to ( T g m - T) −2.8.