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Fil: Forchetti Casarino, Agustin. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Santa Fe. Instituto de Desarrollo Tecnologico para la Industria Quimica. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnologico para la Industria Quimica; Argentina

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; Argentina 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; Argentina Fil: 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; Argentina

The phase inversion (PI) during the bulk polymerization ofthe styrene?polybutadiene system (high impact polystyrenemanufacturing process) is empirically and theoreticallystudied in this article. In the experimental work, a series ofreactions were performed with benzoyl peroxide as initiatorand at temperatures considered of industrial interest (80Cand 90C), varying also the reactor stirring level. PI wasdetermined by offline viscosity measurements and verifiedby scanning transmission electron microscopy. The rheologicalbehavior of each reacting system was analyzed andan empirical correlation to predict its apparent viscosityfrom fundamental reaction parameters was derived. Thiswas achieved successfully for both before and after the PIpoint. Fil: Maffi, Juan Martín. Instituto Tecnológico de Buenos Aires; Argentina Fil: Casis, Natalia. 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; Argentina Fil: Acuña, Pablo. Centro de Investigacion En Quimica Aplicada, Saltillo; México Fil: Morales, Graciela. Centro de Investigacion En Quimica Aplicada, Saltillo; México Fil: 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; Argentina

The performance of three multifunctional peroxide initiators in a bulk high impact polystyrene (HIPS) process was experimentally and theoretically investigated. For the experimental work, a series of batch reactions was carried out, comprising the main stages of an industrial HIPS bulk process using multifunctional initiators with varying functionality and structure: DEKTP (cyclic trifunctional), PDP (cyclic bifunctional) and L331 (linear bifunctional). The theoretical work consisted of the development of a comprehensive, generic yet detailed mathematical model for bulk HIPS polymerization using multifunctional initiators. The model predicts the evolution of the main polymerization variables (including conversion, molecular weights, grafting efficiency) as well as the detailed molecular structure of the polymeric species (free polystyrene, residual polybutadiene and graft copolymer), and the melt flow index of the obtained HIPS. The model was adjusted and validated using experimental results, obtaining a good agreement between measured and predicted values. The model was used to theoretically evaluate the effect of the operating conditions on the molecular and physical characteristics of the obtained polymer. It was found that the use of multifunctional initiators leads to high polymerization rates and high molecular weights simultaneously, while promoting the grafting of styrene onto butadiene, generating a microstructure with salami-type morphologies. Fil: Laganá, María Laura. Instituto Tecnológico de Buenos Aires; Argentina Fil: Maffi, Juan Martín. Instituto Tecnológico de Buenos Aires; Argentina Fil: Berkenwald, Emilio. Instituto Tecnológico de Buenos Aires; Argentina Fil: Acuña, Pablo. Centro de Investigación En Química Aplicada; México Fil: Morales, Graciela. Centro de Investigación En Química Aplicada; México Fil: 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; Argentina

Fil: Karp, Federico. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Santa Fe. Instituto de Desarrollo Tecnologico para la Industria Quimica. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnologico para la Industria Quimica; Argentina

The synthesis of new nanoporous materials based on molecularly imprinted polymers (MIPs) is investigated. The novel procedure combines the non-covalent imprinting method with the colloidal crystal template technique to producemembranes with pre-specified morphology capable of selectively recognizing progesterone. The colloidal crystals made of silica particles were obtained by Langmuir−Blodgett and self-assembly techniques, and exhibited a considerable control of the film thickness. Hydrogel films were prepared by copolymerization of acrylic acid and ethylene glycol dimethacrylate in the presence of 2,2′-azobisisobutyronitrile as initiator. The polymerization took place in the interspaces of the colloidal crystal and after the reactionwas finished the silica particleswere etched with hydrofluoric acid to produce a 3D ordered structure. The nanocavities derived from progesterone were distributed within the walls of the internal structure of the films. The equilibrium swelling properties of the MIPs were studied as a function of crosslinking degree and pH. The poremorphology of the film was analyzed by SEM. The MIP characterizations were accomplished by several techniques, e.g. Fourier transform infrared spectroscopy, DSC and evaluation of their sensing and selective properties.

This work experimentally and theoretically investigates the use of the symmetrical cyclic trifunctional initiator diethyl ketone triperoxide (DEKTP) in the bulk polymerization of styrene (St). The study focused on temperatures of 150 to 200°C, considering chemical initiation by both sequential and total decomposition reactions. The experimental work consisted of a series of isothermal batch polymerizations at higher temperatures, 150 and 200°C, with an initiator concentration of 0.01 mol/L. The mathematical model is based on a kinetic mechanism that includes thermal and chemical initiation (both sequential and total decomposition reactions), propagation, transfer to monomer, termination by combination and re-initiation reactions. Experimental and theoretical results show that the decomposition mechanism of the initiator is modified by the reaction temperature and can be modeled as a set of two parallel reactions with different temperature dependences. The developed mathematical model simulates the bulk polymerization of St in the presence of DEKTP for a wide temperature range (120–200°C). It was found that due to these two decomposition mechanisms, the system may behave as a “dead-end” polymerization system above a certain temperature, yielding low molecular weights and a limiting conversion value. Simulation results indicate the value of this temperature to be about 185°C. Fil: Berkenwald, Emilio. Instituto Tecnologico de Buenos Aires; Argentina Fil: Spies, Cecilia Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentina Fil: Morales, Graciela. Centro de Investigación en Química Aplicada; México Fil: Estenoz, Diana Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina. Instituto Tecnologico de Buenos Aires; Argentina

In this study, we experimentally and theoretically investigated the use of the symmetrical cyclic trifunctional initiator diethyl ketone triperoxide (DEKTP) in the bulk polymerization of styrene. The experimental study consisted of a series of isothermal batch polymerizations at different temperatures (120 and 130°C) with different initiator concentrations (0.005, 0.01, and 0.02 mol/L). A mathematical model was developed to predict the evolution of the reacting chemical species and the produced molecular weight distributions. The kinetic model included chemical and thermal initiation, propagation, transfer to the monomer, termination by combination, and reinitiation reactions. The simulation results predict the concentration of diradicals, monoradicals, and polymeric chains, characterized by the number of undecomposed peroxide groups. The experimental results showed that at reaction temperatures of 120–130°C, initiation by DEKTP produced an increase in the polymerization rates (Rp's) and average molecular weights, depending on the initiator concentration, due to sequential decomposition. The mathematical model was adjusted and validated with the experimental data. The theoretical predictions were in very good agreement with the experimental results. Also, an optimum initiator concentration was observed that achieved high Rp's and high molecular weights simultaneously. For polymerization temperatures of 120–130°C, the optimum concentration was 0.01 mol/L. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

For a batch emulsion polymerization of isoprene at 10 °C in the presence of a chain transfer agent, a previous mathematical model [Minari et al., J. Appl. Polym. Sci. 2010, 116, 590] was extended for predicting the molecular weight distributions of all the generated long-branched molecular topologies; with each topology characterized by the number of tri- and tetra-functional branches per molecule. At the reaction end, and according to the new model predictions, the linear topology remains as the most abundant (with approximate 50% of the total mass), followed by the single trifunctionally-branched topology (with approximate 20% of the total mass). The model can be useful for developing strategies for controlling the distribution of branches/molec., for estimating melt viscosities, etc. Fil: Rodriguez, Virginia Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina Fil: Minari, Roque Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina Fil: Estenoz, Diana Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina Fil: Gugliotta, Luis Marcelino. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina 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

A polybenzoxazine / polysiloxane hybrid has been prepared by sol-gel process and ring-opening polymerization. For this purpose, first a functionalized benzoxazine was synthesized from bisphenol A, paraformaldehyde and 3(trimethoxysilyl) propylamine, with initial molar ratio 1:4:2, and 95% yield. The structure of the monomer was characterized by Fourier Transform Infrared, Spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR). The sol-gel process and curing behavior have been studied by FTIR spectroscopy and Differential Scanning Calorimetry (DSC). The Dynamic Mechanical Analysis (DMTA) of the hybrid material(Bz-PSi) showed higher Tg and storage modulus respect to the conventional polybenzoxazine (Bz-BA). Also, the Thermogravimetric Analysis (TGA) revealed better thermal stability. The high Limiting Oxygen Index (LOI) values (about LOI = 32)confirmed similar effective flame retardance properties of the hybrid material respect conventional benzoxazine. Fil: Spontón, Marisa Elisabet. 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; Argentina Fil: 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; Argentina Fil: Ligadas, G.. Universitat Rovira I Virgili; España Fil: Ronda, J.. Universitat Rovira I Virgili; España Fil: Galià, M.. Universitat Rovira I Virgili; España Fil: Cádiz, V.. Universitat Rovira I Virgili; España

In this study, PLGA particle systems were studied for the controlled release of florfenicol, a broad spectrum antibiotic used in veterinary treatments. The emulsion-solvent evaporation technique was used for particle preparation. To evaluate the particle size, entrapment efficiency, and drug release behavior, factors such as solvent type, emulsification time and methods, and drug to polymer ratio were investigated. The results showed that the use of ethyl acetate and 2.5 min of ultrasonication or 30 min of homogenization can lead to sub-micron and micron-sized particles, respectively. Sizes between 200–300 nm and 2–3 μm were obtained for ultrasonication and homogenization procedures, respectively. Entrapment efficiencies were around 20% for all systems and release profiles were size dependent. In addition, a mathematical model was implemented to simulate the florfenicol transport. The model predicts the florfenicol release and takes into account the particle size, polymer molecular weight, and autocatalytic polymer degradation. Simulation results are in good agreement with experimental results. Fil: Karp, Federico. 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; Argentina Fil: Busatto, Carlos Alberto. 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; Argentina Fil: Turino, Ludmila Noelia. 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; Argentina Fil: Luna, Julio Alberto. 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; Argentina Fil: 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; Argentina

Fil: Polo, Mara Lis. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Santa Fe. Instituto de Desarrollo Tecnologico para la Industria Quimica. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnologico para la Industria Quimica; Argentina

A mathematical model was developed for simulating the batch copolymerization of styrene (St) and methyl methacrylate (MMA) in the presence of polybutadiene (PB). It was adjusted to the measurements of three reactions carried out at 65C, with initial comonomers ratio at the azeotropic condition, THF as solvent, and benzoyl peroxide as initiator. The measurements included: (a) conversions and grafting efficiencies by gravimetry; (b) molecular weight distributions (MWDs) by size exclusion chromatography; and (c) global mass fractions of St in the co- and terpolymer, by UV-Vis spectroscopy. The model predicts the MWDs of the three polymeric components of MBS: free St-MMA copolymer, St-MMA-g-PB graft terpolymer (GT), and residual PB. In addition, it predicts the bivariate chain length distributions of the different GT topologies, with each topology characterized by the number of branches per molecule. Fil: Gutierrez, Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentina Fil: Estenoz, Diana Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentina Fil: Gugliotta, Luis Marcelino. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentina Fil: Vega, Jorge Ruben. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentina. Universidad Tecnologica Nacional; Argentina 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

A novel class of environmentally benign, non-toxic and recyclable materials based on vinylbenzyl thymine (VBT) and an ionically-charged vinylbenzyl triethylammonium chloride (VBA) monomers was studied. Several syntheses of VBT-VBA copolymers at various comonomer ratio and initiator concentrations were carried out at 65 °C using isopropanol as solvent. Samples were taken during the reactions to determine the monomer conversion, chemical composition and molecular weight distribution. The comonomers exhibited similar reactivities and random copolymers with similar chemical compositions were obtained. The curing process involved the irradiation of the copolymer films with a short-wavelength UV light (254nm) for different times, leading to film immobilization on the substrate. The light-induced crosslinking reaction was followed by UV-vis spectroscopy and the immobilization point relative to the gel point was determined. The kinetics of the crosslinking process pointed to a second-order process with respect to the thymine concentration. The experimental results provide complementary information on photo-induced immobilization of VBT―VBA films that are crucial for developing new classes of environmentally benign materials and new energy-saving methods.

This work investigates five reactions between melamine (M) and formaldehyde (F) at pH = 9.0, and with initial F : M ratios of 2. The samples were analyzed by size exclusion chromatography (SEC), volumetric techniques, and (1H and 13C) NMR. Condensation was quantified by the SEC measurements. In the experiments at 38 and 48°C, condensation was almost negligible, and the reversibility of methylolation reactions determined that equilibriums were reached in the ratios between primary, secondary, and tertiary amines. In the experiments at 60, 70, and 90°C, condensation was significant, but in all cases, the mass fraction of single-ringed species was larger than that of species with two or more rings per molecule. The following were estimated by combining the SEC and volumetric measurements: number-average molecular weights, and average functionalities of reactive H's, methylols, methylene bridges, and ether bridges. The dissolution of M in water was essentially instantaneous. The measurements are employed in the next article of this series for adjusting a novel mathematical model. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

A novel mathematical model is presented for the reaction between melamine (M) and formaldehyde (F) at pH = 9.0 and at temperatures between 38 and 90°C. It is based on a kinetic scheme that includes reversible methylolations, irreversible formation of (unsubstituted) methylene bridges, reversible formation of (unsubstituted) ether bridges, instantaneous dissolution of M, and instantaneous equilibrium for the hydration/dehydration of F. The model predicts the distributions of molecular weights and functionalities of the evolving MF resin. Arrhenius expressions were adjusted for the seven kinetic constants on the basis of measurements reported in the first part of this series. Even though the final products contain thousands of different molecular species, 21 of them constitute more than 90% of the total weights. During the initial period with negligible condensation, the undissolved M distorts the distributions of molecular weights and functionalities; but the reversibility of methylolations corrects for such distortion prior to the effective start of condensation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

The bulk prepolymerization of styrene in the presence of polybutadiene for the production of highimpact polystyrene is analyzed and compared with an equivalent solution reaction described by Estenoz et al. in 1999. The heterogeneous model reported by Casis et al. in 2006 is extended to predict the bivariate distributions of the graft copolymer topologies; each topology is characterized by the number of trifunctional branching points per molecule. The developed model assumes polymerization in two phases and requires the adjustment of a single kinetic parameter. Grafting efficiencies determined by solvent extraction/gravimetry are compared with determinations obtained by the deconvolution of size exclusion chromatograms of the total polymer. The chromatographic technique is fast and simple, but it requires a representative polymerization/fractionation model. Fil: Casis, Natalia. 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; Argentina Fil: 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; Argentina 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; Argentina 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; Argentina

The bulk copolymerization of styrene and acrylonitrile in the presence of SB using BPO as initiator was investigated. Reactions were carried out at 80°C with different initial SB concentrations. Global variables, such as conversion and cumulative grafting efficiency of SAN, were determined during the prepolymerization. The isolated non-grafted SAN was also analyzed to determine its average molar masses and composition. A mathematical model was developed, and theoretical predictions were compared with experimental data. A good agreement between measurements and simulations was obtained from a heterogeneous model when BPO was evenly distributed between phases.

Fil: Luciani, Carla Vanesa. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Santa Fe. Instituto de Desarrollo Tecnologico para la Industria Quimica. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnologico para la Industria Quimica; Argentina

Fil: Nicolau, Veronica Viviana. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Santa Fe. Instituto de Desarrollo Tecnologico para la Industria Quimica. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnologico para la Industria Quimica; Argentina

This work presents (in a wider perspective), some of our recent developments in the mathematical modeling and control of bulk polymerization for the production of HIPS. The recent model by Casts assumes the polymerization to be heterogeneous, and it calculates (in two phases) the global molecular structure of the three polymeric components of HIPS (free polystyrene, unreacted polybutadiene, and graft copolymer). At present, a model is being developed capable of estimating the average particle morphology (salami or core-shell). Assuming a continuous bulk HIPS process as homogeneous, Luciani estimated the evolution of the MFI of the final product during changes of grade, with the aim of minimizing the intermediate off-spec product. Finally, an unpublished simulation is presented that describes the transitions between the steady state of a HIPS-grade and that of a general-purpose polystyrene.

Support-catalyst-polymer particles composed of millions of microparticles arranged in cells and having silica nuclei covered with metallocene-methyl alumoxane (MAO) active sites are studied to analyze cell participation during polymerization. Main variables are the changing particle morphology and the kinetic-diffusion effects determined local monomer availability during residence time. The phenomena were studied by means of a mathematical model used to produce a set of predictions for particles polymerizing ethylene in a toluene slurry continuous stirred tank reactor (CSTR) under various operating conditions. This information is employed to predict the micro- and macroparticle behavior in situations designed to explore catalyst activities, monomer availabilities and reactor conditions. Kinetic constants and concentrations range from reference values up to 6 times these figures, with reactor temperatures between 323 and 353 K and particle Reynolds numbers on a 1 to 10 relative scale. Heat transfer and temperature elevation duing polymerization are predicted, with no relevant overheating observed. Morphology changes, in the form of density profiles inside the support-catalyst-polymer particle, are monitored with time, and their interaction with transport and reaction phenomena analyzed. Increasing catalyst activity alone may not produce proportional raises in yield; it appears more efficient to improve the monomer availability instead. High catalyst activity may produce monomer depeletion at inner cell delaying their fragmentation and decreasing local polymer-production.

A novel benzoxazine (BzPFA) with carboxylic acid groups in its structure was synthesized in a two-step process. First, BzPOH monomer was obtained from bisphenol A, paraformaldehyde, and ethanolamine with an initial molar ratio 1:4:2. Then, BzPOH was reacted with maleic anhydride using a stoichiometric 1:1 ratio of oxazine ring:maleic anhydride to produce a mixture of oligomeric species named BzPFA. The products were characterized by nuclear magnetic resonance, size-exclusion chromatography, and Fourier transform infrared spectroscopy. BzPFA presented a weight-average molecular weight of 50,000 g mol−1. Mixtures of the novel precursor and the conventional benzoxazine based on bisphenol A (BzBA) (60:40 and 40:60 weight ratios) were prepared and three different curing conditions were considered in order to study the effect of BzPFA on curing and final properties. Blends exhibited improved properties respect to BzBA even at relatively low curing temperatures. These results can be associated to the network crosslinked by ester bonds that promotes a high rigidity. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46183. Fil: Gilbert, Elangeni Ana. 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; Argentina Fil: Morales, Graciela. Centro de Investigacion En Quimica Aplicada, Saltillo; México Fil: Spontón, Marisa Elisabet. 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; Argentina Fil: 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; Argentina

Polymeric micelles (PMs) composed of self-assembled amphiphilic block copolymers were synthesized from vinylbenzyl thymine (VBT) and vinylbenzyl triethylammonium chloride (VBA) exhibiting improved physical stability. Three diblock copolymers of different chemical compositions and similar molecular weights (polydispersities below 1.5) were obtained via nitroxide mediated radical polymerization. Critical micelle concentration (CMC) was determined by dye micellization method, the shift of the absorption peak of the anionic (EY) due to the interactions with non-assembled chains and auto-assembled copolymers was followed. Polymeric systems exhibited good stability revealing that a higher proportion of cationic monomers in the diblock reduce the CMC. Furthermore,after the core of PMs was photocrosslinked by UV irradiation, the CMC decreases notably. Kinetic release studies using EY dye as probe demonstrated that both, higher VBA ratios in the polymer and higher UV-irradiation, slow down the dye release. Fil: Barbarini, Alejandro Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Física del Litoral; Argentina Fil: Estenoz, Diana Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina Fil: Martino, Debora Marcela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Física del Litoral; Argentina

>A mathematical model, including the main morphological features of the polymerization process, is developed to study olefin polymerization with supported metallocene catalysts. Because the relatively large amount of methyl alumoxane (MAO) usually needed as a cocatalyst represents a disadvantage, the model introduces a scheme that simulates the results of the efforts being made in a supported catalyst to reduce MAO requirements to commercially acceptable levels. Critical fragmentation steps in the initial support-catalyst particles that render all active sites effectively available to the monomer are specifically considered, on the basis of the support morphological characteristics. With the available reaction data, fragmentation representation alternatives are discussed and a scheme proposed. Then, a mathematical model is developed based on the above representation scheme, to calculate monomerconcentration, temperature, and macroparticle-size evolutions. The main features of the scheme are displayed and discussed. Both for laboratory and high-productivity conditions, the model is used to predict changes in macro- and microparticle size, porosity, and concentration distribution. Predictions are employed to evaluate the impact of the initial support microparticle arrangement and fragmentation processes on the overall catalyst performance. Polymer yield, concentration profiles, and temperature transients predicted by the model are presented, showing the model application after verifying its accordance with the available experimental data. Fil: 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; Argentina Fil: Chiovetta, Mario Gabriel. 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; Argentina

This work experimentally and theoretically determines the molecular macrostructure of the polymer mixture that is developed (at relatively low conversions) in a solution polymerization of styrene (St) in presence of polybutadiene (PB). The reaction was carried out at 70°C in a batch-stirred tank reactor. From samples taken along the reaction, the three polymeric components of high-impact polystyrene (HIPS) (i.e., polystyrene PS, residual PB, and graft copolymer) were first separated from each other by solvent extraction. Then, the graft copolymer was ozonized to isolate the St branches. The molecular weight distributions (MWDs) of the total HIPS, the three HIPS components, and the grafted St branches were determined by the size exclusion chromatography (SEC). For the graft copolymer and the total HIPS, the variation of the St mass fraction with molecular weights was also determined by SEC. All measurements were compared with theoretical estimates, and a reasonable agreement is observed. For the theoretical estimates, the mathematical model of Estenoz, D. A.; Valdez, E.; Oliva, H. M.; Meira, G. R. (J Polym Sci 1996, 59, 861) was extended to compare the MWD of the St branches with the MWD of the free PS. For the sought experimental conditions, these two distributions had very similar results but in a bulk industrial process, larger discrepancies are to be expected. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1950–1961, 1999

An industrial bulk process for the continuous production of high-impact polystyrene (HIPS) is mathematically modeled, and the model is validated with actual plant data. The steady states of two commercial HIPS grades were investigated. Polymer samples were taken along the process to measure monomer conversion, styrene (St) grafting efficiency, and free PS molecular weights. The model adequately reproduces the experimental measurements, and it also estimates the molecular macrostructure of the evolving reaction mixture.

This work experimentally and theoretically investigates the use of bifunctional initiators in the synthesis of high-impact polystyrene (HIPS). The experimental design involved a series of nonisothermal bulk polymerizations of styrene (St) in the presence of polybutadiene (PB). The performance of three commercial initiators [2,5-dimethyl −2,5 bis(2-ethylhexanoyl peroxy] hexane or L–256; 2,5 bis(benzoyl peroxy) hexane or L–118; and ethyl 3,3 di(t-butyl peroxide) butirate or L–233] were compared to the performance of a standard monofunctional initiator (terbutylperoctoate or TPBO), and to the blank case (i.e., without initiator). From samples taken along the prepolymerization period, the phase inversion point and the 30% conversion point were estimated. For the final product, the free polystyrene (PS) molecular weights and the St grafting efficiency were measured. A mathematical model was developed that predicts the evolution of the MWDs for the free PS the residual PB, and the graft copolymer, together with the chemical composition distribution for the total graft copolymer. Compared to the monofunctional case, the L–256 initiator induces phase inversion and rubber grafting at low conversions. Also, it shortens the prepolymerization times by around 38%, without affecting the molecular characteristics of the final product. L–118 also shortens prepolymerization time with respect to TBPO; but is not as effective as L–256 or TBPO in promoting rubber grafting. At the polymerization end, the final molecular characteristics are practically independent of the initiator type because most of the polymerization in induced by monomer initiation. Due to its slow decomposition rate, the L–233 initiator is less effective that TBPO for reducing prepolymerization times and for promoting phase inversion. © 1996 John Wiley & Sons, Inc.

A mathematical model for the polymerization of ethylene using silica-supported chromium catalysts is presented. The fundamentals for the physical and chemical representation of the phenomenon are detailed. The emerging mathematical problem is attached and solved using a multiple moving-boundary numerical scheme. Predictions are made using the model for the cases of low and high activity catalysts tested by experiments, and the results used to evaluate the model. The main feature of the model is its structural nature : catalyst characterization and morphology data are used to create a physical scheme that does not require the assumptions concerning particle geometry, usually made in models. The initial catalyst fragmentation process is modeled using a pore-structure scheme based upon porosimetry data. The whole fragmentation sequence is treated as a set of steps that follow the actual rupture process of the initial solid into fragments with irregular shapes. Parameters are evaluated from data for the initial support, and time evolution is followed using a realistic interpretation of the pore filling process. A novel application of moving-boundary solution techniques permits a relatively simple mathematical scheme to handle the transport and reaction processes that take place in the polymerizing particle. Only the results obtained for the experimental laboratory conditions are analyzed. In subsequent parts, the case of thermal effects typical of industrial conditions will be discussed. The results obtained are in excellent agreement with the experimental data.

A mathematical model, including energy balances and thermal effects, for the polymerization of ethylene using silica-supported chromium catalysts is presented. The model is based on a previous work, with the main feature being its structural nature. Catalyst characterization and morphology data are used directly in a physical scheme that does not require the assumptions concerning particle geometry found in other models in the literature. Predictions are made using the model for the cases of high activity catalysts under experimental (laboratory) and industrial reactor conditions. Catalyst fragmentation is modeled as a set of steps that follow the actual rupture process of the initial solid into fragments with irregular shapes. Parameters are evaluated from experimental data for the initial support. From modeling results, mass transfer control is not observed. Neither external mass transport phenomena, nor internal diffusive processes become restrictive for polymerization although monomer concentration decay exists. Temperature rise is relevant because of the high catalyst activity and monomer concentration typical of industrial systems. However, under controlled polymerization conditions, temperature elevation is important but not critical to polymer production. The limiting step in the energy transport process in the particle is the external transfer. The results obtained show a strong influence of reactor conditions upon polymerization reaction and polymer properties, and are in good agreement with the available data.

In our previous publication the detailed molecular macrostructure generated in a solution polymerization of styrene (St) in the presence of polybutadiene (PB) at 60°C, was theoretically calculated. In this work, an extended kinetic mechanism that incorporates monomer thermal initiation, chain transfer to the rubber, chain transfer to the monomer, and the gel effect is proposed, with the aim of simulating a bulk high-impact polystyrene (HIPS) process. The mathematical model enables the calculation of the bivariate weight chainlength distributions (WCLDs) for the total copolymer and for each of the generated copolymer topologies and the univariate WCLDs for the free polystyrene (PS), the residual PB, and the crosslinked PB topologies. These last topologies are characterized by the number of initial PB chains per molecule; copolymer topologies are characterized by the number of PS and PB chains per molecule. The model was validated with published literature data and with new pilot plant experiments that emulate an industrial HIPS process. The literature data correspond to a dilute solution polymerization at a constant low temperature with chemical initiation and a bulk polymerization at a constant high temperature with thermal initiation. The new experiments consider different combinations of prepolymerization temperature, initiator concentration, and solvent concentration. One of the main conclusions is that most of the initial PB is transformed into copolymer. For example, for a prepolymerization temperature of 120°C with addition of initiator, the experimental measurements indicate that the final total rubber mass is approximately three times higher than the initial PB. Also, according to the model predictions, the final weight fractions are: free PS, 0.778; graft copolymer, 0.220; initial PB, 0.0015; and purely crosslinked PB, 0.0005. The final graft copolymer exhibits the following characteristics: average molecular weights, Mn,C = 492,000 and Mw,C = 976,000; average weight fraction of St, 0.722; and average number of PS and PB branches per molecule, 5.19 and 1.13, respectively. © 1996 John Wiley & Sons, Inc.

The radical-induced grafting of styrene onto polybutadiene at 60°C and in dilute solution is theoretically investigated, with the aim of estimating the detailed molecular macrostructure of the evolving polymer mixture. To this effect, the kinetic mechanism proposed by Brydon et al. [J. Polym. Sci. Polym. Chem. Ed., 11, 3255 (1973) and 12, 1011 (1974)] was extended to evaluate the bivariate weight chain-length distribution (WCLD) for each of different copolymer topologies generated along the polymerization. Each molecular topology is characterized by two integers: the number of grafted styrene chains and the number of incorporated butadiene chains. Apart from the bivariate WCLDs for every topology and for the total copolymer, the molecular weight distributions of the accumulated polystyrene and of the unreacted polybutadiene are calculated. The model predictions of global variables (monomer conversion, polymer production, average molecular weights, grafting efficiencies, and average number of graft sites per reacted polybutadiene molecule) closely match the experimental measurements in the cited publications. © 1993 John Wiley & Sons, Inc.

This work investigates a batch and unseeded emulsion polymerization of isoprene at 10°C with n-dodecylmercaptan as chain transfer agent (CTA). The obtained polyisoprene (PI) was analyzed by size exclusion chromatography (SEC) with on-line viscometry. A global polymerization model was adjusted to the measurements of conversion, average particle size, and average molecular weights. The CTA concentration strongly affects the average molecular weights but has a negligible effect on conversion, average particle diameter, and average branching. Due to the combined effects of chain transfers to the polymer and to the CTA, the final molar mass distributions exhibited dispersity indexes higher than 10. The polymerization model predictions on the average degree of branching was combined with an ideal SEC model for adjusting the branching exponent of PI in tetrahydrofuran at 25°C that resulted e = 2.5. A sensitivity analysis showed that +20% errors in w induced variations in e lower than −10%. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010