Control of Molecular Weight Distribution in Emulsion Polymerization Using On-Line Reaction Calorimetry

The molecular weight distribution (MWD) of linear polymers was controlled based on on-line reaction calorimetry. A method to estimate the MWD from reaction calorimetry when chain transfer to a chain-transfer agent is the main termination event was developed and its robustness assessed by simulation. Following this method, the desired final MWD was decomposed in a series of instantaneous MWDs to be produced at different stages of the process. An optimization algorithm was used to calculate the set-point trajectories to produce the desired MWD in a minimum time. A nonlinear model based controller was used to track these trajectories. The control scheme was validated by preparing polystyrene latexes of widely different predefined MWD.