Free‐Radical Polymerization: Homogeneous Systems

Hutchinson, Robin A.; Penlidis, Alexander

doi:10.1002/9780470692134.ch3

Cited by 19 publications

(16 citation statements)

References 150 publications

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“…The kinetic mechanism used is shown in Table . Typical kinetic constants values for styrene‐based copolymerizations were provided by the current literature of CRP . Values for the cross‐propagation rates, r 1 and r 2 , were manipulated in order to provide a composition drift and generate gradient copolymers, which is an example of material whose production if possible by means of CRP techniques.…”

Section: Resultsmentioning

confidence: 99%

Stochastic Modeling of Polymer Microstructure From Residence Time Distribution

Lemos

Melo

Pinto

2015

Macro Reaction Engineering

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Stochastic modeling constitutes a powerful technique to obtain complete distributions of microstructural properties of polymer materials and may help to synthesize polymers with well-defined microstructure, as in the case of controlled radical polymerizations (CRP). However, these techniques have been often applied to describe polymerizations performed in batch or idealized continuous plug flow conditions. The present manuscript describes a Monte Carlo technique that can be used to calculate microstructural properties in polymerization systems performed continuously with arbitrary residence time distributions (RTD), under regime of complete micromixing segregation. The technique approximates the continuous system by a set of batch reactors, operated independently, whose volumes and batch times can be related to the discretized version of the RTD. The technique is applied successfully to describe a styrene-based CRP reaction carried out in an ideal continuous stirred tank reactor and a tubular non-ideal tubular reactor.

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Section: Resultsmentioning

confidence: 99%

Stochastic Modeling of Polymer Microstructure From Residence Time Distribution

Lemos

Melo

Pinto

2015

Macro Reaction Engineering

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“…At a critical point (i.e., when K = K cr as computed using Equation (5) and (6)), termination reactions become diffusion controlled. The expression involving k T , k t,seg , and k t,rd in Equation (15) is used to account for the three contributions to the overall termination rate coefficient by each of the modes of diffusion 23. This second stage of diffusion control leads to the onset of autoacceleration wherein the rate of termination decreases but the rate of propagation for individual chains remains high.…”

Section: Introductionmentioning

confidence: 99%

Application of Parameter Selection and Estimation Techniques in a Thermal Styrene Polymerization Model

Woloszyn

McAuley

2011

Macro Reaction Engineering

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A model is developed to describe thermally‐initiated polymerization of styrene between 100 and 170 °C. The model accounts for generation and consumption of styrene adduct. Chain transfer to adduct is the only transfer reaction used. Autoacceleration is modeled using the break‐point method of Hui and Hamielec. Using formal ranking and parameter selection techniques that account for parameter sensitivity, correlation and uncertainty, 4 of the 40 model parameters are selected for estimation to improve fit between model predictions and data. After estimation, the model predicts conversion data with a standard error of 5%, and provides excellent fit to a MWD curve obtained at 100 °C. Simulation results confirm that high‐temperature degradation reactions are not important in the temperature range of interest.

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“…These reactions occur in addition to the well-known and well-understood set of basic FRP mechanisms consisting of initiation, propagation, termination, and chain transfer [5,6]. This article provides an overview and summarizes recent experimental and modeling efforts by our group and other researchers to improve the understanding of these mechanisms.…”

Section: Introductionmentioning

confidence: 96%

Free‐Radical Acrylic Polymerization Kinetics at Elevated Temperatures

Wang

Hutchinson

2010

Chem Eng & Technol

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Free-radical acrylic homo-and copolymerization kinetics are reviewed, focusing on secondary reactions that impact the polymerization rate and polymer molecular weight (MW) under industrially-relevant synthesis conditions. Dependent on the monomer type (acrylate, methacrylate, styrene), mechanisms that must be considered include chain-end depropagation, monomer self-initiation, formation and reaction of midchain radicals, and incorporation of macromonomers formed by b-scission of midchain radicals. The relative importance of these reactions varies with temperature and, for copolymerization, monomer composition. A comprehensive treatment of these complexities has been completed for polymerizations conducted up to 180°C, but further work is required to extend the applicability of the model to even higher temperatures. IntroductionThe production of low-density polyethylene and associated copolymers at 200-300°C and high pressure is perhaps the bestknown example of high-temperature free-radical polymerization (FRP). However, an increasing number of acrylic resins, produced from a mixture of monomers selected from the methacrylate, acrylate, and styrene families, are also manufactured under higher temperature conditions (>120°C) in homogeneous solution. Low-molecular-weight acrylic resins are the base polymer components for many automotive coatings due to their excellent resistance to chemicals, solvents, ultraviolet light, and abrasion, as well as their exterior durability after crosslinking on the surface of the vehicle [1]. High-temperature conditions are used to produce a variety of other materials for coatings, adhesives, and paints [2]. These conditions are chosen to increase production rates and to decrease (or eliminate) the solvent employed in the formulation while maintaining reasonable solution viscosity [2][3][4].While commercially advantageous, the high polymerization temperatures greatly promote the occurrence of secondary reactions that have a strong impact on polymerization rate and polymer MW, such as monomer self-initiation, chain depropagation, and the formation and subsequent reaction of midchain radicals and unsaturated polymer chains (macromonomers). These reactions occur in addition to the well-known and well-understood set of basic FRP mechanisms consisting of initiation, propagation, termination, and chain transfer [5,6]. This article provides an overview and summarizes recent experimental and modeling efforts by our group and other researchers to improve the understanding of these mechanisms. As most high-temperature acrylic polymerization processes involve multiple monomers, the complexities of including these reactions in copolymerization will also be addressed. An accurate treatment of high-temperature FRP kinetics is a critical component of larger-scale process models used to predict the influence of the operating conditions on reaction rate and polymer properties, guide the selection and optimization of standard operating conditions for existing and new polymer grades, and guide process ...

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Free‐Radical Polymerization: Homogeneous Systems

Cited by 19 publications

References 150 publications

Stochastic Modeling of Polymer Microstructure From Residence Time Distribution

Stochastic Modeling of Polymer Microstructure From Residence Time Distribution

Application of Parameter Selection and Estimation Techniques in a Thermal Styrene Polymerization Model

Free‐Radical Acrylic Polymerization Kinetics at Elevated Temperatures

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