Optimal Processes for Crystal Polystyrene

Anionic Polymerization of Styrene in a Tubular Reactor

“…Since the polymerization rate for anionic polymerization is faster than that of radical polymerization, the viscosity changes quickly, giving an even greater tendency toward elongation than in radical polymerization. For stable operation of a tubular reactor, the maximum axial velocity was recommended to be less than 10 times the average velocity . However, the present modeling results indicate that it usually exceeded a factor of 10 in our experiments.…”

“…The free radical polymerization of styrene is sufficiently understood to allow a priori design of polymerization reactors. See, for example, Mallikarjun and Nauman. , This is not yet the case with anionic polymerization, but progress is being made. Using existing correlations, model predictions were in fair agreement with experimental results.…”

Solution viscosity of polystyrene at conditions applicable to commercial manufacturing processes

“…The previously used Harkness correlation remains fairly accurate, even for the extended range of data included in this paper. Thus, design studies based on the correlation (10)(11)(12)(13) are unlikely to contain major errors.…”

“…This result was used in the modeling studies of Agawal (10), Chen and Nauman (11), and Mallikarjun and Nauman (12,13). The data base used by Harkness generally spans the region of industrial interest, but his correlation does not include effects due to polydispersity or to nonzero shear rates.…”

Scaleup of Polymerization Processes

“…The dramatic transition from a controlled reaction to a thermal runaway corresponds to a mere 1 mm difference in tube diameter. Although inlet and wall temperatures can be varied, reaction in a large-diameter tube is not feasible for this and similarly energetic reactions absent an excellent control system [6]. A detailed model of this polymerization in an open tube (the model consists of simultaneous, partial differential equations for composition, temperature, and velocity) shows that hydrodynamic instabilities can arise in the absence of static mixers due to large viscosity differences between the wall and centerline.…”