Gel effect in free radical polymerization: Model discrimination of its cause

O'Neil, Gregory A.; Wisnudel, Marc B.; Torkelson, John M.

doi:10.1002/aic.690440522

Cited by 32 publications

(49 citation statements)

References 30 publications

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“…O'Neil et al [65,66] examinaram experimentalmente a consistência da teoria do volume livre, quando aplicada para descrever o efeito gel em sistemas de polimerização via radical livre. Os autores mostraram que a teoria do volume livre prediz com sucesso o efeito gel, e que a diminuição do volume livre pode ser relacionada com o aumento da viscosidade do meio reacional, à medida que o monômero é convertido a polímero.…”

Section: Correlações Para Os Efeitos Gel E Vítreounclassified

Uma revisão sobre os processos de polimerização em suspensão

2007

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Resumo: Inúmeros processos podem ser utilizados para produção de materiais poliméricos. Cada processo apresenta características peculiares, que permitem produzir resinas com as mais variadas propriedades, visando a diferentes aplicações do material polimérico final. Os processos de polimerização em suspensão são bastante empregados para produção de resinas poliméricas por apresentarem muitas vantagens, como a facilidade de separação, fácil remoção de calor e controle de temperatura e, principalmente, pelos baixos níveis de impureza e de aditivação no produto final. Por isso, processos de polimerização em suspensão são apropriados para obtenção de produtos para aplicações biotecnológicas e médicas, dentre outras. O objetivo principal deste trabalho é apresentar uma discussão dos aspectos fundamentais inerentes aos processos de polimerização em suspensão, visando a uma compreensão do efeito das principais variáveis de processo sobre o desempenho de polimerizações em suspensão. Mostra-se também que a espectroscopia do infravermelho próximo (NIRS) pode ser muito útil para permitir o monitoramento e o controle em tempo real de processos de polimerização em suspensão, para a obtenção de materiais poliméricos com características especiais. Palavras-chave: Polimerização, suspensão, espectroscopia, infravermelho próximo. A Review on Suspension Polymerization ProcessesAbstract: Several processes can be employed for manufacturing polymer materials. Each process presents some intrinsic features that lead to production of resins with peculiar properties, which define the end-use application of the final polymeric material. Suspension polymerization processes are extensively used because of their many advantages, such as the easy separation of the polymer particles, easy removal of the heat of reaction, easy temperature control and low levels of impurities and additives in the final polymer material. For this reason, suspension polymerization processes are suitable to produce polymer resins for biotechnological and medical applications. The main objective of this work is to discuss the fundamental aspects of suspension polymerization processes, focusing upon the effects of the main process variables on the performance of suspension polymerizations. Additionally, it is shown that near infrared spectroscopy (NIRS) can be useful for monitoring and real time control of suspension processes, allowing for production of polymer beads with controlled morphology.

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Section: Correlações Para Os Efeitos Gel E Vítreounclassified

Uma revisão sobre os processos de polimerização em suspensão

2007

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“…Also this effect is known as Norrish-Smith effect [5], Trommsdroff effect [6], Norrish-Trommsdroff effect [7] and gel effect [7,8].…”

Section: Auto-acceleration and Gel Effectmentioning

confidence: 99%

Thermochemistry of Acrylamide Polymerization: An Illustration of Auto-acceleration and Gel Effect

Abu-Thabit¹

2017

WJCE

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Addition polymerization of alkenes is an exothermic process due to the relief of the bond strain from C-C double bonds (π bonds) in the monomer molecules. Control of exothermic reactions is crucial for preventing runaway reactions/explosions in the industrial setting. This experiment was designed for undergraduate students to demonstrate the exothermic nature of addition (chain-growth) polymerization and to estimate the enthalpy of polymerization using adiabatic calorimetry technique. Acrylamide (AAM) was polymerized using ammonium persulfate (APS) and Tetramethylethylenediamine (TMEDA) as redox initiators at room temperature. The concentration of AAM monomer was varied in the range of 5-25 wt. %, and the heat of polymerization was calculated from the recorded temperature rise (ΔT). The enthalpy of AAM polymerization (∆Hp) was estimated to be ≈ 16.5-19 kcal/ mole, depending on the monomer concentration. Enthalpy of polymerization was increased with increasing the monomer concentration due the auto-acceleration effect, which was clearly observed for solutions with AAM concentrations of ≥ 20 wt. %. The auto-acceleration phenomenon was identified from the fast and non-linear increase in the rate of temperature rise which reached a maximum of (0.5°C/ s) for solutions with AAM of 25 wt. %. For AAM concentrations of ≥ 20 wt. %, the auto-acceleration was accompanied by the polymer gelation (gel effect) due to the formation of the high molecular weight polyacrylamides.

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“…The reaction rate in the suspension polymerization system can be diffusion‐controlled (gel effect). There are many models available in the literature to describe this effect . These methods account for the gel effect by reducing the termination constant as the conversion and viscosity increase during the reaction .…”

Section: Mathematical Modelmentioning

confidence: 99%

Mathematical Modeling of Molecular Weight Distributions in Vinyl Chloride Suspension Polymerizations Performed with a Bifunctional Initiator through Probability Generating Functions

Castor

Sarmoria

Asteasuain

et al. 2014

Macro Theory & Simulations

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This paper presents a mathematical model to describe the evolution of the molecular weight distribution (MWD) in vinyl chloride (VCM) free‐radical suspension polymerizations performed with a bifunctional initiator, 1,3‐di(2‐neodecanoylperoxyisopropyl) (DIPND). The model yields, as a function of time, the mass balances for the distinct phases, the monomer conversion, the number‐ and mass‐average molecular weights and the complete MWD of both the growing and dead polymer chains. In order to describe the MWD, the model uses probability generating functions (pgf) to transform the mass balance equations into a reduced and finite set of model equations. As shown throughout many examples, the MWD's of the final polymer resin is little sensitive to the presence of the linear symmetrical bifunctional initiator.

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Gel effect in free radical polymerization: Model discrimination of its cause

Cited by 32 publications

References 30 publications

Uma revisão sobre os processos de polimerização em suspensão

Uma revisão sobre os processos de polimerização em suspensão

Thermochemistry of Acrylamide Polymerization: An Illustration of Auto-acceleration and Gel Effect

Mathematical Modeling of Molecular Weight Distributions in Vinyl Chloride Suspension Polymerizations Performed with a Bifunctional Initiator through Probability Generating Functions

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