CRITICAL PROPERTIES FOR GELATION IN FREE-RADICAL CROSS-LINKING COPOLYMERIZATION

A kinetic model was used to predict the molecular weight developments and the critical properties in free-radical crosslinking copolymerization. The predictions of the model were compared to the experimental data reported previously. Agreement of the kinetic model with experiments is satisfactory for both low and high crosslinker contents. The model parameters indicate increasing extent of shielding of pendant vinyl groups as the reaction proceeds due to the increasing number of multiple crosslinkages. The calculation results indicate that the real critical exponents can only be observed in the region epsilon < 10(-2)-10(-3) where experimental studies are very difficult. Outside of this region, the apparent critical exponent gamma describing the divergence of the weight-average molecular weight was found to deviate from the classical value due to the conversion dependent kinetics of free-radical crosslinking copolymerization.