Mis treinta y cinco años en el grupo de polímeros del INTEC en Santa Fe

Es para mí un gran honor el escribir esta reseña. Si bien no estoy a la altura de la mayor parte de los científicos argentinos cuyas historias ya fueron publicadas, acepto gustoso en elaborar esta autobiografía científica comentada, como forma de contribuir a la memoria histórica de las instituciones a las que pertenecí, y en especial al Grupo de Polímeros y Reactores de Polimerización del INTEC que tengo el honor de dirigir desde su creación informal hace ya 35 años.Fil: Meira, Gregorio Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin

Molecular Weight Distributions in Ideal Polymerization Reactors. An Introductory Review

The ultimate aim of polymerization reaction engineering is the production of polymers with tailor-made properties. An introductory review into this field is presented, with emphasis on the effects on the molar mass distribution (MMD), of the sought combination of polymerization mechanism, reactor type, and reactor control. Three ideal polymerization mechanisms are analyzed: free-radical, living anionic, and step-growth. Living anionic and step-growth polymerizations are similar in that their growing chains remain reactive while inside the reactor; and for these systems the narrowest MMDs are produced in reactors with narrow residence time distributions (RDT); i.e.: batch or continuous tubularreactors. In contrast, in conventional free-radical polymerizations, the polymer molecules grow in a fraction of a second and thereafter remain inactive while inside the reactor. In this case, the RTD does not affect the MMD, and the homogeneous continuous stirred-tank reactors provide the narrowest MMDs. Representative mathematical models of polymerization reactors are useful for: a) quantifying the interrelationships between their numerous inputs and outputs; and b) developing open- and closedloop strategies for increasing reactor productivity and product quality.Fil: Meira, Gregorio Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina. Universidad Nacional del Litoral; ArgentinaFil: Oliva, H.. Universidad del Zulia; Venezuel

Mechanisms and conditions that affect phase inversion processes. A review.

The phenomenon of phase inversion occurs in liquid-liquid dispersions foundin a variety of chemical engineering fields. From simple oil-water mixtures tocomplex polymeric systems, the operating variables that affect this physicalphenomenon are discussed in this work. The contribution on this matter by alarge number of researchers is critically assessed, outlining both coherent andconflicting results. A detailed review of the mechanisms by which phase inversiontakes place is also provided. While this subject has been studied for thepast 50 years, this multivariate nonlinear process is not yet comprehensivelyunderstood, and this review article aims to describe the conclusions so farreached to provide insight for future research.Fil: Maffi, Juan Martín. Instituto Tecnológico de Buenos Aires; ArgentinaFil: Meira, Gregorio Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Estenoz, Diana Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin

Reduction of Transients between Steady States in the Continuous Production of High-Impact Polystyrene

This work theoretically investigates the reduction of transients during changes of grade in a continuous plant for the production of high-impact polystyrene (HIPS). A mathematical model was developed that predicts the global molecular structure and the melt flow index (MFI). The switching times of the off-specs accumulation period were selected on the basis of the admissible MFI ranges. Smoother transitions and reduced off-specs can be produced through a simple readjustment (with respect to the original plant policy) of the two intermediate chain transfer agent (CTA) loads into the batch dissolver. For the transitions that involve a large difference in their MFIs, the off-specs can be reduced by 60%, with respect to the original plant policy, by including a transient feed of CTA into an intermediate stirred reactor.Fil: Luciani, Carla Vanesa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Estenoz, Diana Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Meira, Gregorio Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Oliva, Haydée M.. Universidad del Zulia; Venezuel

Free Radical Polymerization: Heterogeneous Systems

Bulk free-radical polymerizations are carried out in the absence of a dispersion medium, and without (or with a very little) solvent. Many technical polymers such as LDPE, LLDPE, PVC, PS, HIPS, PMMA, nylon, and polyester are manufactured in bulk processes. Compared with suspension, emulsion, or solution processes, bulk polymerizations exhibit a higher reactor performance, higher product purity, and reduced transfer reactions to solvents or additives. The disadvantages are related with the high process viscosity, which in turn generates problems of heat removal, mixing, pumping, and reactor wall fouling, by film formation. Some bulk polymerizations (e.g., the production of crystal or general purpose PS) are homogeneous because the produced polymer is amorphous and completely soluble in the monomer. In contrast, PVC soon precipitates from its monomer. In the HIPS process, the heterogeneity results from the incompatibility between the initial PB prepolymer and the generated PS chains. Many thermoplastics are heterogeneous (or heterophase), because they contain liquid or rubber dispersions that improve their physical properties with respect to those of the continuous brittle phase. Examples of this are the softening of PVC by the presence of phthalate droplets, and the improved toughness of HIPS or ABS by addition of PB-based rubber particles. This chapter will focus on the (heterogeneous, bulk, and free-radical) polymerizations leading to the production of HIPS and PVC.Fil: Meira, Gregorio Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Kiparissides, Costas. Aristotle University of Thessaloniki; Greci

Polymerization under Modulation

Polymerization was an early focus for periodic operation. Ray (1968) and Laurence and Vasudevan (1968) observed that the molecular weight distribution of a polymer may be modified by periodically varying the concentrations of either monomer, initiator, or transfer agent fed to a polymerization reactor. Since those original studies, a large literature on this application of periodic operations has developed. Concepts and terminology differ considerably from applications considered here-to-fore, so a short introduction to polymerization begins this chapter.Fil: Meira, Gregorio Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Silveston, P.L.. University of Waterloo; Canad

Polímeros: Introducción a su Caracterización y a la Ingeniería de la Polimerización

Los seres vivos estamos constituidos por macromoléculas complejascomo las proteínas y el ADN, y desde la prehistoria el hombre haceuso de polímeros naturales como la madera, la lana y el caucho.Pero este libro trata principalmente sobre los polímeros sintéticos,que la humanidad comenzó a producir masivamente a partir demediados del siglo XX. En la primera parte se describen las principalestécnicas de caracterización de polímeros, que se relacionan con susestructuras moleculares, con su morfología, y con sus propiedadesfísico-mecánicas. En la segunda, se describen los distintos procesosde polimerización, con énfasis en su modelado matemático yoptimización, así como en la obtención de polímeros con propiedadesespeciales. El área de los polímeros es multidisciplinaria e involucratanto a las ciencias básicas (química, física y biología) como a variasde las aplicadas (ingeniería química, ingeniería de materiales ybiotecnología). Esta obra está dirigida a estudiantes universitarios(de grado y de posgrado) y para profesionales de la industria queestén interesados en la ciencia y la tecnología de los polímeros.Fil: Meira, Gregorio Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Gugliotta, Luis Marcelino. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin

SEC of Simple Polymers with Molar Mass Detection in the Presence of Instrumental Broadening. Computer Simulation Study on the Recuperation of Unbiased Molecular Weight Distributions

This theoretical work presents a correction procedure for calculating an unbiased MWD when analyzing a linear homopolymer by size exclusion chromatography with molar mass detection. The fractionation and the measurements are ideal, but the chromatograms are distorted by a nonuniform and skewed instrumental broadening (IB), and are contaminated with a zero-mean random noise. The main assumption is that the molecular weight calibration is linear in the chromatogram range. The following phenomenological procedure was proposed: (i) independently correct the mass- and molar mass chromatograms for IB through a robust inverse filtering technique; (ii) estimate the unbiased calibration from the ratio of the corrected chromatograms; (iii) adjust a straight line to the mid-values of that cal-ibration; and (iv) estimate the unbiased MWD from the linear calibration and the corrected mass chromatogram. For the chromatogram inversions, a minimum sized broadening matrix was selected and a singular value decomposition technique was applied. The following effects were evaluated: of an increased measurement noise, of uncertainties in the range of the measured chromatograms, and of systematic errors in the IB function. The method fails for very narrow MWDs.Fil: Vega, Jorge Ruben. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Meira, Gregorio Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin