Examinando por Materia "POLIMERIZACION"
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- Artículo de Publicación PeriódicaBulk polymerization of styrene using multifunctional initiators in a batch reactor: A comprehensive mathematical model(2016-02) Berkenwald, Emilio; Laganá, María Laura; Acuña, Pablo; Morales Balado, Graciela Elizabeth; Estenoz, Diana"A detailed, comprehensive mathematical model for bulk polymerization of styrene using multifunctional initiators - both linear and cyclic - in a batch reactor was developed. The model is based on a kinetic mechanism that considers thermal initiation and chemical initiation by sequential decomposition of labile groups, propagation, transfer to monomer, termination by combination and re-initiation reactions due to undecomposed labile groups. The model predicts the evolution of global reaction variables (e.g, concentration of reagents, products, radical species and labile groups) as well as the evolution of the detailed complete polymer molecular weight distributions, with polymer species characterized by chain length and number of undecomposed labile groups. The mathematical model was adjusted and validated using experimental data for various peroxide-type multifunctional initiators: diethyl ketone triperoxide (DEKTP, cyclic trifunctional), pinacolone diperoxide (PDP, cyclic bifunctional) and 1,1-bis(tert-butylperoxy)cyclohexane (L331, linear bifunctional). The model very adequately predicts polymerization rates and complete molecular weight distributions. The model is used to theoretically evaluate the influence of initiator structure and functionality as well as reaction conditions."
- Artículo de Publicación PeriódicaExperimental and theoretical study of the use of multifunctional initiators in the high impact polystyrene bulk process(2018-02) Berkenwald, Emilio; Laganá, María Laura; Maffi, Juan M.; Acuña, Pablo; Morales Balado, Graciela Elizabeth; Estenoz, Diana"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."
- PósterFluid dynamics of the phase inversion process in the bulk polymerization of high impact polystyrene(2021) Maffi, Juan M.; Estenoz, Diana"In the synthesis of HIPS, phase inversion (PI) is the critical point at which a dispersed PS-rich phase becomes a continuous matrix, leaving behind a PB-rich phase as dispersed particles that may contain occluded PS-rich droplets inside (occlusions). The size and shape of these particles essentially determine the mechanical properties of the material, which makes PI a critical point during the reaction. In this work, the most popular mechanism for PI – an imbalance between coalescence and break-up of dispersed particles – is assessed through a population balance model, coupled with a heterogeneous polymerization model. Results are adjusted and discussed with experimental evidence gathered from TEM images."
- Tesis de doctoradoMathematical modeling of discontinuous bulk styrene polymerization processes using multifunctional initiators(2016) Berkenwald, Emilio; Estenoz, Diana; Marqués, Dardo"En esta tesis, se estudia el uso de iniciadores multifuncionales para la polimerización en masa de estireno. El objetivo general es desarrollar modelos matemáticos detallados, y a la vez genéricos, que permitan describir la compleja fisicoquímica de estos procesos y predecir las variables principales de polimerizacióon, la evolución de la estructura molecular y las caracteríticas físicas del producto obtenido. La labor teórica se complementa con trabajos experimentales que permiten ajustar y validar los modelos propuestos."
- Artículo de Publicación PeriódicaMechanisms and conditions that affect phase inversion processes. The case of high-impact polystyrene(2019) Maffi, Juan M.; Casis, Natalia; Acuña, Pablo; Morales Balado, Graciela Elizabeth; Estenoz, Diana"The phase inversion during the bulk polymerization of the styrene-polybutadiene system (HIPS manufacturing process) is empirically and theoretically studied in this article. In the experimental work, a series of reactions were performed with benzoyl peroxide as initiator and at temperatures considered of industrial interest (80ºC and 90ºC), varying also the reactor stirring level. Phase inversion was determined by offline viscosity measurements and verified by scanning electron micrography in transmission mode (STEM). The rheological behavior of each reacting system was analyzed and an empirical correlation to predict its apparent viscosity from fundamental reaction parameters was derived. This was achieved successfully for bothbefore and after the phase inversion point."
- Artículo de Publicación PeriódicaNew advances in the mathematical modeling of the continuous bulk process for the production of high-impact polystyrene using multifunctional initiators(2019-03) Laganá, María Laura; Berkenwald, Emilio; Acuña, Pablo; Enríquez Medrano, Javier; Morales Balado, Graciela Elizabeth; Estenoz, Diana"New advances in the mathematical modeling of the bulk continuous high-impact polystyrene (HIPS) process are presented. The model consists of three modules that allow the simulation of: (1) a polymerization reactor train, (2) a devolatilization (DV) stage, and (3) structure–properties relationships. The model is based on a kinetic mechanism that includes thermal initiation, chemical initiation by sequential decomposition of a multifunctional initiator, propagation, transfer to monomer, transfer to rubber, termination by combination and re-initiation, as well as high temperature crosslinking and oligomer generation reactions. The present model is comprehensive from a kinetic perspective, since it can be used to simulate a HIPS process using initiators of any functionality and structure. The model is adjusted and validated using previously unpublished experimental data for bulk continuous HIPS polymerization in a pilot-scale plant. The experimental work includes a series of polymerizations using three different multifunctional initiators: (1) luperox-331 M80 (L331), (2) pinacolone diperoxide, and (3) diethyl ketone triperoxide. The pilot plant comprised the main stages of an industrial HIPS process: prepolymerization, finishing and DV. Theoretical results show a good agreement with the experimental measurements".
- Tesis de doctoradoNuevos desarrollos en el modelado matemático del proceso continuo para la producción en masa de polímeros de estireno en presencia de elastómeros =(2022-07) Laganá, María Laura; Estenoz, Diana; Stripeikis, Jorge"El objetivo general de esta tesis es investigar aspectos aún no dilucidados en el área de la ingeniería del proceso de polimerización en masa de estireno (St) en presencia de elastómeros para la producción de Poliestireno de alto impacto (HIPS). La investigación se enfoca en el entendimiento y modelado matemático de los fenómenos fisicoquímicos involucrados, en el estudio y empleo de nuevas técnicas de modelado para la simulación de sistemas complejos, y en la optimización de los procesos. Se pretende lograr desarrollos que contribuyan a diseñar y operar los procesos industriales continuos con alto grado de comprensión, y optimizados desde el punto de vista de la productividad y de la calidad del producto final."
- Artículo de Publicación PeriódicaOn the evolution of particle size distributions during the bulk synthesis of high-impact polystyrene using PBM: Towards morphology and phase inversion prediction(2022-01-16) Maffi, Juan M.; Estenoz, Diana"The mechanism of the phase inversion (PI) process that occurs during the bulk polymerization of High Impact Polystyrene (HIPS) is studied in this article. Transmission electron micrographs (TEM) were obtained for different operating conditions, varying initiator concentration, temperature, and stirring speed from a previous work. Particle size distributions were retrieved from such micrographs, and were compared to theoretical predictions. To this end, a population balance model, coupled with a heterogeneous polymerization module, was developed. The evolution of particle growth, break-up and coalescence is discussed to assess the breakage/coalescence imbalance that is thought to occur at the inversion point. Results indicate that a different criterion for PI seems to be needed in this system."
- PósterPhase inversion prediction during the bulk synthesis of high-impact polystyrene: a fluid-dynamic approach(2021-11) Maffi, Juan M.; Estenoz, Diana"High-Impact Polystyrene (HIPS) is a heterogeneous material constituted by a rubber (PB) particles dispersed in a vitreous polystyrene (PS) matrix. Two typical morphologies are usually identified: ‘salami’ (larger rubber particle with several PS occlusions) or ‘core-shell’ (smaller particle with one large occlusion). The industrial continuous bulk HIPS process involves four main stages: dissolution, pre-polymerization, finishing and evolatilization. During the pre-polymerization, the mixture consists of a continuous PB-rich phase where PS-rich droplets grow as the reaction proceeds. At a critical point, the dispersed vitreous phase reaches a volume such that it becomes the continuous phase, through a co-continuous transition. This is the phase inversion (PI) point, and the material morphology is essentially defined at this stage, characterized by a sudden drop in the mixture’s apparent viscosity."
- Tesis de doctoradoTheoretical and experimental study on the phase inversion process during the bulk synthesis of high impact polystyrene(2021-03-26) Maffi, Juan M.; Estenoz, Diana; Berkenwald, Emilio"In this thesis, the phenomenon of phase inversion is studied from a qualitative, theoretical and experimental point of view. The general objective is to contribute to the understanding of this fuid- and thermodynamic phenomenon in its particular application in the case of HIPS. The aim is to develop a physical-mathematical model capable of predicting the point of phase inversion during the reaction from the reactor conditions. Among the different alternatives, approaches based on the rheological evolution of the reaction mixture and others based on the fuid dynamics of the dispersed system are explored."