Did you know… that changing the rate of monomer addition in a semi-batch emulsion polymerization can affect your product properties? Monomer feed rates may be varied for different reasons. Increasing monomer feed rates can reduce the overall batch cycle time and increase productivity. If you are making core-shell or other structured particles, controlling monomer feed rates is an important strategy for obtaining the desired morphology.
However key polymer particle properties, including molecular weight, degree of branching and extent of crosslinking, are influenced by the monomer concentration inside the particles, which in turn is largely determined by the rate at which monomers are fed, coupled with reaction temperature. Higher monomer concentrations result in longer polymer chains (higher molecular weight) being made at any instant during the polymerization. Conversely, lower monomer concentrations result in shorter polymer chains (lower molecular weight) being made at any instant. However lower monomer concentrations can also increase the rates of branching and crosslinking.