Abstract
This paper deals with the multiobjective optimization problem, applied to the free radical polymerization of styrene. The objectives taken into account and proportionally combined into a scalar objective function are: maximization of the monomer conversion or achievement of a desired value for conversion, minimization of the polydispersity index, minimization of the reaction time, obtaining of a polymer with desired polymerization degree. Using different values of the weights, the objectives which have to be reached and, also, their importance within the polymerization problem are established. The decision variables are the initial concentrations of the two initiators (benzoyl peroxide and tertbutylperbenzoate) and temperature represented by two or three isothermal steps. For solving the optimization problem, several methods are used and compared: sequential quadratic programming, genetic algorithm and a hybrid method obtained by successive use of the two above methods. This last solving alternative improves the results of the optimization procedure. The possibility of changing the weight values of the proposed objectives is a favorable opportunity to consider technological criteria for the optimization problem. Keywords: optimization, free radical polymerization, polydispersity index