Dynamic Modeling and Simulations of Molecular Weight Distributions In Continuous Stirred Tank Reactors for Solution Polymerization of Methyl Methacrylate

Abstract

The finite molecular weight moments (FMWM) technique, originally developed for calculating the complete molecular weight distribution (MWD) in batch free radical polymerizations, is extended here to simulate transient changes in MWD in a series of continuous flow stirred-tank solution polymerization reactors. Unlike the classical method of molecular weight moments, which only calculates molecular weight averages, the FMWM technique provides a simple and effective means to calculate the whole shape of the polymer molecular weight distribution curve, even during the transient period of reactor operations in continuous processes. In this work, the solution polymerization of methyl methacrylate is used as a model system to demonstrate that the FMWM technique can successfully simulate transient MWDs, particularly bimodal distributions of polymer molecular weight resulting from varying reactor operating conditions in a series of two consecutive continuous stirred-tank reactors operating at different temperatures. The simulation results reveal several interesting aspects of how polymer MWD changes over time in each reactor.