Polymer reactors and molecular weight distribution: Part II. Free radical polymerization in a batch reactor

Hamielec, A. E.; Hodgins, J. W.; Tebbens, K.

doi:10.1002/aic.690130610

Cited by 62 publications

(34 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The works of Hamielec and co-workers represent notable exceptions to the above. Using carefully controlled batch experi ments, MWD determination by gel permeation chromatography (GPC), Hamielec et al (25) obtained good agreement with theoretical calcula tions based on parameters at low viscosities. Duerksen et al (17) did the same for CSTR's.…”

Section: Reaction Mechanismsmentioning

confidence: 55%

Polymerization Reaction Engineering

Chappelear

Simon²

1969

Advances in Chemistry

View full text Add to dashboard Cite

The rational design of a reaction system to produce a desired polymer is more feasible today by virtue of mathematical tools which permit one to predict product distribution as affected by reactor type and conditions. New analytical tools such as gel permeation chromatography are beginning to be used to check technical predictions and to aid in defining molecular parameters as they affect product properties. The vast majority of work concerns bulk or solution polymerization in isothermal batch or continuous stirred tank reactors. There is a clear need to develop techniques to permit fuller application of reaction engineering to realistic nonisothermal systems, emulsion systems, and systems at high conversion found industrially. A mathematical framework is also needed which will start with carefully planned experimental data and efficiently indicate a polymerization mechanism and statistical estimates of kinetic constants rather than vice-versa./^wing to a recent increase in theoretical treatments of polymerization kinetics, processes, and reactor design, chemical engineers are becoming increasingly active in a field where physical chemists primarily published. This paper reviews the theoretical tools now available and attempts to identify the work needed to make a fundamental approach more useful in practice. The broader field of chemical reactor engineering is itself relatively new, with the first modern text by Brotz (10) and by Walas (56) appearing in 1958 and 1959, respectively. Of the several thousand pages that have appeared since 1958, however, only a few deal with polymerization reactors, hardly sufficient recognition of their commercial importance. The recent activity seems triggered by the avail-'Also staff member,

show abstract

Section: Reaction Mechanismsmentioning

confidence: 55%

Polymerization Reaction Engineering

Chappelear

Simon²

1969

Advances in Chemistry

View full text Add to dashboard Cite

show abstract

“…Hamielec and coworkers [3,4] investigated, both experimentally and theoretically, the free-radical bulk and solution polymerization of styrene at different temperatures (e.g., 50-75 8C), in the presence of a chemical initiator (2,2 0 -azoisobutyronitrile, AIBN). Tefera et al [5] also investigated, both experimentally and theoretically, the free-radical suspension polymerization of styrene at different temperatures (i.e., 70, 75, and 80 8C) and initiator concentrations (i.e., AIBN: 0.15-0.45 wt.-% of styrene).…”

Section: Introductionmentioning

confidence: 99%

A Comprehensive Kinetic Model for the Combined Chemical and Thermal Polymerization of Styrene up to High Conversions

Kotoulas

Krallis

Pladis

et al. 2003

Macro Chemistry & Physics

View full text Add to dashboard Cite

In the present study, a comprehensive mathematical model is developed for the free‐radical polymerization of styrene to predict the polymerization rate and the molecular‐weight distribution of the polymer. The kinetic model accounts for both chemical and thermal radical generation and, thus, can be employed over an extended range of polymerization temperatures (e.g., 60–200 °C). The thermal initiation mechanism includes the reversible Diels‐Alder dimerization of styrene, radical formation via the reaction of the Diels‐Alder adduct with monomer, the formation of dead trimers, and the initiation of new polymer chains. Moreover, a comprehensive free‐volume model is employed to describe the variation of termination and propagation rate constants as well as of the initiator efficiency with respect to the monomer conversion. The cumulative molecular‐weight distribution of the polystyrene is calculated by the weighted sum of all the ‘instantaneous’ weight chain‐length distributions formed during the batch run. The capabilities of the present model are demonstrated by a direct comparison of model predictions with experimental data on monomer conversion, number‐ and weight‐average molecular weights, and molecular‐weight distribution. It should be noted that previously published kinetic models cannot describe the combined thermal and chemical free‐radical polymerization of styrene in terms of a unified, fundamental, kinetic model, which further underlines the significance of this study.Predicted and experimental weight‐average molecular weights with respect to monomer conversion (experimental conditions same as in Figure 1).magnified imagePredicted and experimental weight‐average molecular weights with respect to monomer conversion (experimental conditions same as in Figure 1).

show abstract

“…For quality control, where perturbations are very small, this is satisfactory. As a general specification this is more questionable since some properties depend more strongly on the tail of the MWD (5,6,7).…”

Section: Product Specificationsmentioning

confidence: 97%

“…Experimental runs were simulated with a selected MTD and a perfectly mixed RTD by calculating the outlet conditions-i.e., monomer concentration and the moments of the molecular weight dis tribution of polymer products. It was shown that the parameters of the MTD could be obtained from the outlet conditions of a known reactor system using the Rosenbrock pattern search method as described by Wilde (5) to minimize the deviation between the calculated sum of first three moments of the molecular weight distribution and that of the experimental values.…”

Section: = F~e(a*)c(**)damentioning

confidence: 99%

Polymerization Kinetics and Reactor Design

Shinnar

Katz

1972

Advances in Chemistry

View full text Add to dashboard Cite

An informal review is given of the author's view of the present state of engineering knowledge in polymerization kinetics and the present state of the art in the design of polymerization reactors. The discussion focuses on key areas where information for reactor design is needed and relates them to the design and scale-up of the reactor. Special emphasis is given to the effect of reactor configura tion. Optimization methods and the importance of proper control strategy are also discussed.*"phe recent advances in polymerization kinetics and design of polymerization reactors have been aptly summarized in recent reviews (1-4) which include most of the published articles. We therefore decided that instead of repeating these efforts we would devote this review to taking stock of our opinion of where we stand today and what problems must be solved to bring the design of polymerization reactors to the same level as conventional reactor design.Basically, polymerization is a complex chemical reaction, and there fore most of the concepts developed with respect to the design of re actors for such reactions apply also to the design of polymerization reactors. Thus, what are the significant differences of polymerization as compared with other complex chemical reactions that merit special attention? Let us briefly consider what is the information generally needed for the successful design and control of a chemical reactor.Assume we already have a process giving a desired product. What we need for design is:( 1 ) Specifications and tolerances for the product quality, the yields needed, etc.(2) An engineering kinetic model allowing us to predict the effect of changes in the process parameters (temperature, inlet concentration, transport processes ) on the yield and desired products. 56 57(3) A description of the transport processes occurring in the re actor; in other words, a flow model and an evaluation of the effect of transport processes on the kinetics.With this information in hand, we can then undertake to consider: (4) A suitable design configuration allowing safe scale-up and easy control.(5) Optimization of design and operating conditions. (6) Control strategy to ensure conformance to specifications. The body of this review takes up these points in order. Product SpecificationsPerhaps the most characteristic feature of polymerization reactor engineering is the fact that in a majority of cases the specifications are not given in terms which are suitable for reactor design. Let us assume for a moment that we have a simple polymerization process, where only one type of polymer is possible and that we know the kinetics sufficiently to predict the effect of all variables. What we are going to predict are molecular weight distributions (MWDs). However, product specifica tions are given in completely different terms: mechanical strength, elec trical properties, corrosion resistance, performance in molding and extrusion equipment, etc. While for this simple case all these properties should be completely specified by the MWD, wha...

show abstract

Polymer reactors and molecular weight distribution: Part II. Free radical polymerization in a batch reactor

Cited by 62 publications

References 6 publications

Polymerization Reaction Engineering

Polymerization Reaction Engineering

A Comprehensive Kinetic Model for the Combined Chemical and Thermal Polymerization of Styrene up to High Conversions

Polymerization Kinetics and Reactor Design

Contact Info

Product

Resources

About