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Abstract: In order to implement nonlinear control, nonlinear system identification must be performed, however, there are open questions concerning this field of process control, for example, experimental planning, model structure selection, parameter estimation, and validation. Therefore, the study of nonlinear model identification is a relevant unsolved problem that needs to be handled for nonlinear control synthesis. This paper presents the use of bifurcation theory, dynamic and stability analysis for nonlinear identification, and control of polymerization reactors. Peroxide‐initiated styrene‐solution polymerization reactors (lumped‐distributed) are investigated: batch, continuous stirred‐tank reactor (CSTR), and tubular reactors. Open and closed loop analyses are carried out using jacket temperature and weight average molecular weight setpoints as the bifurcation parameters. Phenomenological mathematical models, neural network nonlinear models, and an experimental data from a polymerization unit are employed for validating the proposed methodology in order to implement confident nonlinear controllers. [ABSTRACT FROM AUTHOR]

Simulation and experimental studies are carried out for peroxide-initiated styrene solution polymerization in a lumped-distributed reactor. Weight-average molecular weight (intrinsic viscosity measurements) and conversion (density data) are the output signals, while the manipulated variables are jacket reactor temperature and feed modifier ( tert-dodecylmercaptan) concentration. A simple in-line viscometrical method makes the in-line control of weight-average molecular weight in solution polymerization feasible, using independent conversion measurements from an in-line densitometer. Successful closed-loop servo and regulatory control results are obtained. [ABSTRACT FROM AUTHOR]

Poly(ethylene terephthalate- co-isophthalate) (PETI) prepolymer was submitted to solid state polymerization (SSP) at 184-230°C in a fixed bed reactor, to study the evolution of morphological changes during the process. Short reaction times were selected to investigate crystallization phenomena during nonisothermal (heating) and isothermal SSP phases. More specifically, multiple PETI melting behavior was observed and attributed to secondary crystallization, the rate of which increased significantly with SSP temperature. Reaction time was also found to exert a positive effect on solid-phase perfection of secondary crystals, leading at each temperature to melting points close to the value of bottle-grade poly(ethylene terephthalate). Finally, the mass fraction crystallinity of the SSP grades was found to comply with the crystal morphology encountered. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 [ABSTRACT FROM AUTHOR]

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