Control of molecular weight distribution in emulsion polymerization using on-line reaction calorimetry

The molecular weight distribution (MWD) of linear polymers was controlled b ased on on-line reaction calorimetry. A method to estimate the MWD from rea ction 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 o ptimization algorithm was used to calculate the set-point trajectories to p roduce the desired MWD in a minimum time. A nonlinear model based controlle r was used to track these trajectories. The control scheme was validated by preparing polystyrene latexes of widely different predefined MWD.