Heterogeneous bulk polymerization of styrene in the presence of polybutadiene: Calculation of the macromolecular structure

Abstract

A mathematical model is presented that simulates the polymerization of styrene in the presence of polybutadiene (PB) for producing high-impact polystyrene (HIPS) via the heterogeneous bulk process. The model follows the polymerization in two phases; and calculates in each phase the main reaction variables and the molecular structure of the three polymeric components: free polystyrene (PS), unreacted PB, and graft copolymer. Two polymerizations (at 90 and 120°C) were carried out and simulated. The model was validated with measurements of the monomer conversion, the grafting efficiencies, and the average molecular weights.

Partition of tert-dodecyl mercaptan in systems containing styrene, polystyrene, and polybutadiene. Its effect on the macromolecular characteristics of high-impact poly styrene

“…Figure 1 is reproduced from Casís et al [2], and it (crudely) describes the reaction path through a ternary St/PS/PB diagram. First, 5-10% w/w of grated PB are dissolved in St. Industrial recipes typically include other compounds such as solvents and mineral oil to lower the viscosity, and chain transfer agents (CTAs) to reduce the polymer molecular weights.…”

“…The final HIPS properties are essentially determined by the particle morphology and by the global molecular structure of the polymer mixture [5][6][7][8]. [2].…”

“…In spite of the relatively low mass transfer between phases of polymers and other reagents at relatively low monomer conversions, the bulk HIPS process has been considered in thermodynamic equilibrium [2,3,9]. The HIPS process presents a formidable challenge for measuring the partition of species.…”

“…Generally, the models have assumed the reaction mixture as homogeneous, and only 2 works have considered its heterogeneity [2,10]. Ludwico and Rosen [10] considered the homopolymerization of St in the 2 phases, neglecting that most of the initial PB is transformed into GC.…”

“…In addition, for samples taken along the 2 investigated polymerizations, monomer conversion, grafting efficiency, and free PS molecular weights were measured. Theoretical work involved first to model the species partitions through the Flory-Huggins theory [1]; and then, to combine such partition model with a polymerization model extended from that by Casís et al [2]. Theoretical estimations were in good agreement with experimental determinations.…”