Fundacao para a Ciencia e a Tecnologia (FCT) Ministry of Science and Technology of Portugal European Community (FEDER); Grant Number: POCI-PPCDT/EQU/60483/2004
This chapter contains section titled: Introduction Polymerization Kinetics and Modeling Industrial Step-Growth Products, Processes and Modeling Summary
Chapter 5 Suspension Polymerization Costas Kotoulas, Costas KotoulasSearch for more papers by this authorCostas Kiparissides, Costas KiparissidesSearch for more papers by this author Costas Kotoulas, Costas KotoulasSearch for more papers by this authorCostas Kiparissides, Costas KiparissidesSearch for more papers by this author Book Editor(s):José M. Asua, José M. Asua Professor of Chemical Engineering, Institute for Polymer Materials (POLYMAT), The University of the Basque Country, SpainSearch for more papers by this author First published: 01 January 2007 https://doi.org/10.1002/9780470692134.ch5Citations: 5 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Summary This chapter contains section titled: Introduction Surface Active Agents Mixing Phenomena The "Bead" Suspension Polymerization Process The "Powder" Suspension Polymerization Process Population Balance Modeling Physical Properties and Phase Equilibrium Calculations Effect of Operating Conditions on PSD Scale-Up of Suspension Polymerization Reactors Citing Literature Polymer Reaction Engineering RelatedInformation
Aqueous emulsion polymerization is one of the most commonly used techniques in industry for the production of polymer latexes. In this contribution, we present photoinitiated polymerization-induced self-assembly (photo-PISA) based on aqueous visible light-induced reversible addition-fragmentation chain transfer (RAFT)-mediated emulsion polymerization at room temperature. A wide range of morphologies including spheres, worms, and vesicles have been achieved at room temperature by modulating reaction parameters. Additionally, this method enables access to inorganic nanoparticles-loaded vesicles by adding inorganic nanoparticles at the beginning of the polymerization. Finally, an oxygen-tolerant RAFT-mediated emulsion polymerization has been developed, allowing the synthesis of polymer nano-objects at low volumes (e.g., in a 96-well plate). This study is expected to expand the scope of photo-PISA for the preparation of various block copolymer nano-objects in water at room temperature.
Chapter 1 Introduction to Polymerization Processes José M. Asua, José M. AsuaSearch for more papers by this author José M. Asua, José M. AsuaSearch for more papers by this author Book Editor(s):José M. Asua, José M. Asua Professor of Chemical Engineering, Institute for Polymer Materials (POLYMAT), The University of the Basque Country, SpainSearch for more papers by this author First published: 01 January 2007 https://doi.org/10.1002/9780470692134.ch1Citations: 2 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Summary This chapter contains section titled: Microstructural Features of Polymers and their Effect on Properties Classes of Polymerizations Polymerization Techniques Main Commercial Polymers Polymerization Reactors Citing Literature Polymer Reaction Engineering RelatedInformation
AbstractPolymers are among the largest manufactured industrial products. Their extremely diversified properties render a widespread presence possible in everyday life. Polymers can be synthesized either by homogeneous or heterogeneous processes. This article focuses on the homogeneous procedures. The first part of the article summarizes the polymerization of monomers containing at least one carbon–carbon double bond or carbon–carbon triple bond. This is followed by a description of the environmentally accepted and biocompatible poly(lactic acid)s and epoxide–carbon dioxide alternating copolymers. The next two paragraphs focus on special procedures, living and enzymatic polymerization, by which polymers can be synthesized with exotic architectures. The article concludes is finished with the description of step‐growth polymerizations of aromatic systems.
The behaviour of mesoporous silica as a support for anchored catalytic species depends on its physical and chemical surface properties, particularly those related with the hydroxyl groups. #An earlier version of this paper was presented at ECOREP II, 2nd European Conference on Reaction Engineering of Polyolefins, Lyon, France, July 1–4, 2002. In this report, the number and nature of hydroxyl groups of a commercial silica sample calcined at different temperatures have been determined by titration with triethylaluminium and IR, respectively. The preparation of supported metallocene catalyst has been studied by different ways. The calcination temperature affects deeply the ability of the support to anchor the different species involved in this catalytic system. The polymerization reactions carried out using silica and MAO/silica supports show how the chemistry of the silica surface plays a determinant role in the immobilization of this catalytic system.
Low resolution Raman spectroscopy (LRRS) offers a convenient way to monitor many different polymerization processes and reactor environments. LRRS can be used as an additional tool for process control to determine the conversion inside the reactor in real time without disruption to the reaction. Critical to polymerization monitoring, the efficiency of LRRS eliminates the lag between taking samples and calculating conversion. For each system, the phenyl ring of styrene or polystyrene provides an internal reference, which can be used to eliminate fluctuations in laser intensity. This paper demonstrates that the LRRS system can monitor seeded emulsion homopolymerizations in batch and semi‐batch as well as second stage emulsion polymerizations with some acceptable level of confidence.
We have developed software to simulate the development of non-equilibrium latex particle morphologies produced by seeded emulsion polymerization. The diffusion of second stage polymer radicals within seed particles controls the development of morphology in a large number of systems. Knowledge of the conditions present within the latex particles during the reaction is required in order to model this diffusion process, and this makes it necessary to first simulate the kinetics of the polymerization. The program considers both the water phase and particle phase reactions, and can simulate polymerizations carried out under either batch or semi-batch conditions. The model predictions agree well with experimental results both in terms of the polymerization kinetics and the development of particle morphology.
Shortly after joining the Lehigh University Chemical Engineering Department in 1965, I began the normal ritual of trying to secure external research funding, an activity that was less important in ...
A well-mixed model has been formulated to study the steady-state high pressure free-radical homo- and copolymerization of ethylene and vinyl acetate in an industrial multi-feed multi-zone autoclave reactor system. Using a realistic set of kinetic mechanisms and coefficients, the multizone system is modeled as a simple set of well-mixed tank reactors in series. Results from this representation are compared to experimental data in order to estimate apparent initiator efficiencies in each zone. The model is used to calculate monomer conversion and initiator consumption rate, number and weight average molecular weights, and short and long chain branching frequencies at the exit point of each zone and the whole reactor. The effects of zone temperature, feed temperature, and initiator decomposition kinetics on the steady-state reactor performance and polymer properties are considered and simulation results are compared with the industrial data. While estimated initiator efficiencies provide a clear indication of imperfect mixing in the system, the model representation is still able to provide a reasonable estimate of polymer properties.
A general mathematical model for emulsion copolymerization processes in batch reactor is presented. The model predicts the time‐history of monomer conversion, average particle size, copolymer composition and number of particles. The model was tested and validated with experimental data of four different copolymerization systems: S/MMA (styrene/methyl methacrylate), S/BA (styrene/butyl acrylate), MMA/BA (methyl methacrylate/butyl acrylate) and MMA/VA (methyl methacrylate/vinyl acetate). The influence of several process variables, such as initiator concentration, emulsifier concentration, monomer‐to‐water ratio, and composition has been examined. Model predictions presented satisfactory agreement with the experimental data. Despite the model simplicity and the reduced number of adjustable parameters, the model accounts for the basic features of emulsion polymerization processes and can be useful for practical applications.
In the present study a comprehensive experimental investigation on the batch and semi‐batch emulsion terpolymerization of methyl methacrylate/butyl acrylate/acrylic acid (MMA/BuA/AA) is reported. Batch experiments were carried out in a fully automated pilot‐scale reactor system to analyze the effect of polymerization temperature, anionic surfactant and initiator concentrations on the polymerization rate, average particle size, copolymer composition and glass transition temperature of the polymer. In addition, a series of semi‐batch experiments were performed under monomer starved conditions to assess the effect of seven process variables, (e.g., concentrations of anionic, nonionic surfactants and initiator, polymerization temperature, agitation rate, impeller type and addition time of initiator/pre‐emulsion mixture) on the polymerization rate, average particle size, copolymer composition, glass transition temperature and MWD of the polymer.
A model‐based methodology is proposed to describe fragmentation of polymer particles during the very early stages of heterogeneous olefin polymerization reactions. The method is based on the analysis of the particle capacity to release the amount of energy that is accumulated in its interior during the polymerization, due to the fast polymer production. The balance between the rates of energy accumulation and dissipation inside the polymer particle is calculated with the help of a dynamic mathematical model of the prepolymerization reaction. The combination of the presented fragmentation criteria and of the dynamic model may allow one to design the prepolymerization step more precisely and to predict the morphology of the final polymer particles as a function of the initial catalyst particle diameter, reactor temperature, reactor pressure and concentration of active sites. Numerical examples are presented for gas and slurry propylene polymerizations. #An earlier version of this paper was presented at ECOREP II, 2nd European Conference on Reaction Engineering of Polyolefins, Lyon, France, July 1–4, 2002.
The effects of agitation in emulsion copolymerization have been studied using a semibatch emulsion copolymerization recipe that gave a latex with ca. 44 wt% solids. The two-stage polymerization process consisted of an in situ seed-formation step followed by copolymerization of the continuously added n-butyl methacrylate and N-methylol acrylamide monomers under monomer-starved conditions. A 2-dm(3) glass reactor and Rushton turbine agitators of different diameters (4, 6 and 8 cm) were used in the study. Agitation influenced the particle number at the end of the seed stage. This influenced properties like latex viscosity, the amount of water-soluble polymer, and the particle size in the final latex. Analysis of the water-soluble polymer using NMR spectroscopy showed that it was mostly a homopolymer of N-methylol acrylamide. With the 4 cm diameter agitator, the mixing of the pseudoplastic latex was poor during the feed stage. Formation of a zone of poor mixing could be observed on top of the fluid in the reactor, when the monodisperse particles in the latex formed an iridescent structure. Poor emulsification of the added n-butyl methacrylate monomer resulted in a greater amount of water-soluble polymer.
The control of particle morphology is an essential part of producing high quality latex products for applications in coatings, adhesives, impact modifiers, and medical diagnostics, among others. A great variety of formulation and process variables are available to manipulate the particle structure and many different morphologies have been created. Techniques to characterize these morphologies are varied, but electron microscopy of both whole and sectioned particles is the most common one used. Atomic force microscopy is gaining in utility and often two or more characterization methods are simultaneously used to gain clarity of interpretation. A great deal of basic understanding of the factors controlling the morphology has been achieved by applying equilibrium thermodynamics to phase separated particles in aqueous media. Interfacial tensions at the polymer‐water interface and at the polymer–polymer interface, along with crosslinking density are found to be the dominant factors controlling the equilibrium morphology. In turn there is a significant number of formulation variables which determine the interfacial tensions and the crosslinking density. Successful models have been developed and applied to a number of different polymer systems. Much less progress has been made in understanding the development of non‐equilibrium morphologies where the possible number of particle structures is essentially infinite. Here, characterization techniques become somewhat less precise in identifying exact structure and further work is needed to advance this capability. In the dynamic reaction environment of the latex process the morphology develops within very viscous phases and is a result of competitive reaction and diffusion processes. Some progress has been made to quantitatively describe these phenomena, but more work is needed. This is even more evident when extension to carboxylic and hybrid (e.g. polyurethane/acrylic) latices is desired.
Emulsion polymerisations are mostly carried out as (semi‐)batch processes in stirred tanks. In ab‐initio emulsion polymerisation the product properties in terms of particle concentration and particle size distribution strongly depend on the course of the nucleation stage. The course of the nucleation stage is strongly related to the quality of emulsification and the temperature of the reaction mixture. The influence of temperature on the particle size distribution was investigated for completely isothermal as well as for non‐isothermal operation. Reaction calorimetry has been chosen as a tool to define an operating window for control of the nucleation stage in emulsion polymerisation. It was demonstrated that reaction calorimetry is a very poweful tool to define operational details for complete control of the nucleation process in emulsion polymerisation in stirred tanks accurately and quickly. Colloidal stability of the latex is an important issue during the stage of particle growth by simultaneous polymerisation and monomer absorption from the monomer droplets. It was demonstrated that a proper recipe for the production of a colloidally stable latex can be developed in a short time with reaction calorimetry.
