Molecular weight distribution of styrene polymerization in a starved feed reactor

摘要

A starved feed reactor is a semi-batch polymerization reactor where initiator and monomer are fed slowly into a fixed amount of solvent. The polymerization is carried out isothermally at elevated temperatures. Initiator decomposes instantaneously and monomer polymerizes immediately. The molecular weight and molecular weight distribution are effectively controlled by the feed ratio of monomer to initiator. This paper presents a study on the molecular weight distribution of styrene polymerization in a starved feed reactor. The molecular weight distribution model parameters are regressed with the help of experimental data. Although the solids fraction in the starved feed reactor is high (>50%), the viscosity is not high, and the `gel effect' is weak because of the lower molecular weight of the products. We found that the termination rate constant is a power function of the molecular weight, the radicals terminate via 100% combination, and the thermal initiation can be neglected although the reaction temperature is high. The calculated results indicate that in the starved feed reactor, the long-chain assumption needs modification so that a more accurate model can be set up.