Abstract: A starved feed reactor (SFR) is a semi-batch polymerization reactor where initiator and
monomer are fed slowlyinto a fixed amount of solvent. The polymerization is carried out
isothermally at elevated temperatures. The added initiatordecomposes instantaneously and
the added monomer polymerizes immediately. The molecular weight (MW) and molecularweight
distribution (MWD) of the product polymer can be effectively controlled by the feed ratio
of monomer to initiator. Thispaper presents a study on the MWD of styrene polymerization in
a SFR. The MWD model parameters are regressed withexperimental data. Although the solids
fraction in the SFR is high(higher than 50%), viscosity is not too high and the "gel
effect"is weak due to the low molecular weight of the products. It is found that the
termination rate constant is a power function ofmolecular weight, radicals terminate via
100% combination, the thermal initiation can be neglected even at high reactiontemperature
studied. And calculated results indicate that in the SFR,the validity of the long chain
assumption becomes doubted. It appearsthat other alterative assumption should be found for
an improved model.

Key words: starved feed reactor, molecular weight distribution, styrene, radicalpolymerization

摘要： A starved feed reactor (SFR) is a semi-batch polymerization reactor where initiator and
monomer are fed slowlyinto a fixed amount of solvent. The polymerization is carried out
isothermally at elevated temperatures. The added initiatordecomposes instantaneously and
the added monomer polymerizes immediately. The molecular weight (MW) and molecularweight
distribution (MWD) of the product polymer can be effectively controlled by the feed ratio
of monomer to initiator. Thispaper presents a study on the MWD of styrene polymerization in
a SFR. The MWD model parameters are regressed withexperimental data. Although the solids
fraction in the SFR is high(higher than 50%), viscosity is not too high and the "gel
effect"is weak due to the low molecular weight of the products. It is found that the
termination rate constant is a power function ofmolecular weight, radicals terminate via
100% combination, the thermal initiation can be neglected even at high reactiontemperature
studied. And calculated results indicate that in the SFR,the validity of the long chain
assumption becomes doubted. It appearsthat other alterative assumption should be found for
an improved model.

关键词: starved feed reactor;molecular weight distribution;styrene;radicalpolymerization