Artículos de publicaciones periódicas

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Bulk 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."
Experimental 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."
Mechanisms 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."
New 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".

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