Numerical simulation of effects of operating conditions on the molecular weight of polypropylene using a response surface method

A L₄₆3⁵ Box-Behnken design was used for developing a model to predict and optimize the molecular weight (M_w) of polypropylene (PP); a second-order polynomial regression equation was derived to predict responses. The significance of variables and their interactions were tested by means of the ANOVA with 95% confidence limits; the standardized effects were investigated by Pareto chart, the optimum values of the selected variables were obtained by analyzing the response surface contour plots. The optimized M_w value of 1.217×10⁵ g/mol was very close to the industrial value ((1.22±0.004)×10⁵ g/mol) at the optimum values.