A Mathematical Model for the Styrene-Methyl Methacrylate Copolymerization in the Presence of Polybutadiene

GUTIÉRREZ, C.; ESTENOZ, D. A.; GUGLIOTTA, L. M.; VEGA, J. R.; MEIRA, G. R.

Village Rio das Pedras (RJ), Brasil

Congreso; Enpromer 2005, 4th Mercosur Congress on Process Systems Engineering; 2005

The batch copolymerization of styrene (St) and methyl methacrylate (MMA) in the presence of polybutadiene (PB) is theoretically investigated, with the aim of simulating the solution and bulk processes. A mathematical model is presented that enables to calculate: 1) global variables such as monomer conversion, polymer production, grafting efficiencies, copolymer compositions, average molecular weights, and average number of grafted chains per reacted PB molecule; and 2) the macromolecular structure of the evolving polymer mixture (the molecular weight distributions (MWDs) of the free St-MMA copolymer, residual PB, and St-MMA-g-PB terpolymer). The model is an extension of a previous mathematical model by Estenoz et al. [J. Appl. Pol. Sci., 74, 1950-1961, 1999] for the homopolymerization of St in the presence of PB. The model was validated with experiments that consider dilute solution and bulk copolymerizations carried out at a constant low temperature (65 °C), with THF as solvent, benzoyl peroxide as initiator, and a comonomer ratio of St-MMA close to the azeotropic composition. For comparison, the copolymerization of St-MMA without PB was also considered. Samples were taken along the reactions to determine: a) total monomer conversion and grafting efficiencies, by gravimetry; b) global copolymer compositions (as mass fraction of St) by UV; and c) MWDs of the polymer mixture by multi-detection size exclusion chromatography (SEC). The complete set of experimental runs was adequately simulated using a single set of kinetic parameters.