A THEORETICAL INVESTIGATION OF THE PRODUCTION OF BRANCHED COPOLYMERS IN CONTINUOUS STIRRED-TANK REACTORS

A comprehensive mathematical model for free-radical copolymerization r eactions has been developed for a homogeneous continuous stirred tank reactor. The present model is based on a fairly general copolymerizati on scheme accounting for the formation of linear and branched copolyme r chains. Both chain transfer to polymer and terminal double bond reac tions are considered in order to predict the long chain branching freq uency. Changes in molecular weight, composition and degree of branchin g occurring during the copolymerization reaction are modelled using th e method of moments. To break-down the dependence of the moment equati ons on higher order moments two different closure methods are consider ed. The predictive capabilities of the model are examined in relation to the solution copolymerization of methyl methacrylate with vinyl ace tate. It is shown that both chain transfer to polymer and terminal dou ble bond reactions significantly contribute to the broadening of the m olecular weight and degree of branching distributions. Furthermore, th e terminal double bond reaction affects significantly the copolymer nu mber-average molecular weight and the concentration of terminal double bonds.