José M. Asua

Polymeric dispersions : principles and applications

Preface. List of Contributors. Nomenclature. Mechanisms for Radical Entry and Exit. Aqueous-Phase Influences on Polymerization R.G. Gilbert. Particle Growth in Emulsion Polymerization, Determination of Proportion Rate Constants and Monomer Concentration A.M. van Herk. Stability of Polymer Colloids R.H. Ottewill. Particle Nucleation at the Beginning of Emulsion Polymerization K. Tauer, I. Kuhn. Particle Size Distributions E.M. Coen, R.G. Gilbert. Network Formation in Free-Radical Emulsion Polymerization D. Charmot. Polymerization at High Conversion D. Kukulj, R.G. Gilbert. Preparation of Latexes Using Miniemulsions M.S. El-Aasser, C.M. Miller. Microemulsion Polymerization F. Candau. Dispersion Polymerization E.D. Sudol. Metallocene Catalysts in Dispersed Media J.B.P. Soares, A.E. Hamielec. Thermodynamic and Kinetic Aspects for Particle Morphology Control D.S. Sundberg, I.G. Durant. Latex Particle Morphology. The Role of Macromonomers as Compatibilizing Agents P. Rajatapiti, et al. Characterization of Particle Morphology by Solid-State NMR K. Landfester, H.W. Spiess. Scattering Techniques - Fundamentals R.H. Ottewill. Application of Scattering Techniques to Polymer Colloid Dispersions R.H. Ottewill. Optical Spectroscopy on Polymeric Dispersions W.-D. Hergeth. Monitoring Polymerization Reactors by Ultrasound Sensors M. Morbidelli, et al. On-Line Characterization Methods W.-D. Hergeth. Transport Phenomena in Emulsion Polymerization Reactors J.B.P. Soares, A.E. Hamielec. Reaction Engineering for Emulsion Polymerization G.W. Poehlein. The Loop Process C. Abad, et al. Open-Loop Control of Polymerization Reactors J.R. Leiza, J.M. Asua. Feedback Control of Emulsion Polymerization Reactors J.R.Leiza, J.M. Asua. Overview of Uses of Polymer Latexes A.J. De Fusco, et al. Film Formation J. Richard. Latex Paint Formulations J.A. Waters. Encapsulation of Inorganic Particles A.M. van Herk. Some Trends in the Preparation and Use of Reactive Lattices J.J.G.S. van Es, et al. Reactive Surfactants K. Tauer. Synergistic Interactions Among Associative Polymers and Surfactants R.D. Jenkins, D.R. Bassett. Latex Applications in Paper Coating Do Ik Lee. Polymer Colloids for Biomedical and Pharmaceutical Applications C. Pichot, et al. Interactions of Proteins with Polymeric and Other Colloids W. Norde. Index.

Reactive surfactants in heterophase polymerization

This work reviews the publications concerning the use of polymerizable surfactants (surfmers) in heterophase polymeriza-tion in terms of the mechanisms relevant to the process. The goal was to gain some insight into these mechanisms and to help the reader on the way in trying to find a suitable surfmer and to apply it in an appropriate way for a specific polymerization system.

Waterborne Polyurethane−Acrylic Hybrid Nanoparticles by Miniemulsion Polymerization: Applications in Pressure-Sensitive Adhesives

Waterborne polyurethane-acrylic hybrid nanoparticles for application as pressure-sensitive adhesives (PSAs) were prepared by one-step miniemulsion polymerization. The addition of polyurethane to a standard waterborne acrylic formulation results in a large increase in the cohesive strength and hence a much higher shear holding time (greater than seven weeks at room temperature), which is a very desirable characteristic for PSAs. However, with the increase in cohesion, there is a decrease in the relative viscous component, and hence there is a decrease in the tack energy. The presence of a small concentration of methyl methacrylate (MMA) in the acrylic copolymer led to phase separation within the particles and created a hemispherical morphology. The tack energy was particularly low in the hybrid containing MMA because of the effects of lower energy dissipation and greater cross-linking. These results highlight the great sensitivity of the viscoelastic and adhesive properties to the details of the polymer network architecture and hence to the precise composition and synthesis conditions.

Reactive surfactants in heterophase polymerization. VI. Synthesis and screening of polymerizable surfactants (surfmers) with varying reactivity in high solids styrene—butyl acrylate—acrylic acid emulsion polymerization

Several polymerizable surfactants (surfmers) have been used in the semi-continuous emulsion copolymerization of styrene, butyl acrylate, and acrylic acid. Three of the (anionic) surfmers (sodium 11-crotonoyl undecan-1-yl sulfate, sodium 11-methacryloyl undecan-1-sulfate, and sodium sulfopropyl tetradecyl maleate) were prepared in house with purities between 53 and 82%. Physicochemical properties such as the critical micelle concentration, the adsorption isotherm, and the specific adsorption area were determined. The surfmers were then used with constant addition profiles in semicontinuous reactions, and the instantaneous conversions of the main monomers determined. The particle size, amount of coagulum, surface tension, and stability against electrolyte solutions of the latices were evaluated. Films were cast of some of the latices, and the visual appearance and water adsorption were assessed.

Seeded semibatch emulsion polymerization of butyl acrylate : Effect of the chain-transfer agent on the kinetics and structural properties

The effect of dodecane-1-thiol on the kinetics, gel fraction, level of branches, and sol molecular weight distribution of the seeded semibatch emulsion polymerization of n-butyl acrylate carried out at 75 °C was investigated. The gel fraction was strongly affected by the content of the chain-transfer agent (CTA). The sol weight-average molecular weights decreased with increasing CTA concentration, whereas no effect on the kinetics and the level of branches was observed. The experimental data were analyzed with a mathematical model of the process that was able to catch fairly well the effect of the process variable. In addition, adhesive tests were carried out to check the effect of the gel fraction on the adhesive properties.

Dynamic optimization of semicontinuous emulsion copolymerization reactions: composition and molecular weight distribution

Abstract Iterative dynamic programming (IDP) is used to compute optimal monomer and chain transfer agent feed profiles to produce polymer with specified copolymer composition and molecular weight distribution. The approach used allows the implementation of constrained optimization procedures for systems described by complex mathematical models, as those needed for proper description of emulsion copolymerization reactors, especially when the computation of the whole molecular weight distribution is desired. The proposed approach is applied to the semicontinuous methyl methacrylate (MMA)/butyl acrylate (BuA) emulsion copolymerization in stirred tank reactors, using dodecanethiol as chain transfer agent (CTA). It is shown that this technique allows the effective computation of feed policies for the production of copolymers with constant composition and well-defined molecular weight distributions.

Revisiting Chain Transfer to Polymer and Branching in Controlled Radical Polymerization of Butyl Acrylate

Acrylic monomers undergo chain transfer to polymer during polymerization leading to branched and even gelled polymers. It has been experimentally demonstrated that the extent of branching is higher for conventional free radical polymerization than for controlled radical polymerization (ATRP, RAFT, NMP) and this has been qualitatively explained in terms of the differences in the concentrations of highly reactive short-chain radicals between controlled and conventional radical polymerizations. Contrary to this explanation, in this work, it is quantitatively demonstrated that the short transient lifetime of the radicals, i.e., the time between activation and deactivation of the radical in controlled radical polymerization, is the cause for the low level of branching in these polymerizations.

On-line calorimetric control of emulsion polymerization reactors

Abstract Reaction calorimetry was used to monitor and control unseeded semi-batch emulsion copolymerization of VAc and BuA. An external PC, using the information derived from a commercial reaction calorimeter, calculated on-line the thermal and material balances of the calorimetric reactor, and thus the monomer conversions. For a desired copolymer composition profile, previously calculated conversion-dependent monomer feed profiles were used to determine the rates of monomer addition every 20 seconds. Gas chromatography and gravimetry confirmed that copolymers having the desired variable composition profiles were successfully obtained. The control strategy devised lends itself to polymer quality control and safe operation, since variable monomer inhibitor levels or sudden inhibition during the reaction do not lead either to the formation of off-composition polymer nor to monomer accumulation in the reactor. Furthermore, the rate of polymerization can be reduced by fixing upper limits for monomer concentrations in the polymer particles, useful in cases where the minimum-time optimal feed profile, which corresponds to maximum swelling, might lead to thermal runaway.

Dynamic optimization of non-linear emulsion copolymerization systems: Open-loop control of composition and molecular weight distribution

Time optimal monomer and chain-transfer agent feed profiles were computed and implemented experimentally for the simultaneous control of copolymer composition and molecular weight distribution in non-linear emulsion copolymerization systems. Iterative dynamic programming was used for the off-line calculation of the optimal feed policies. This approach can deal with constrained optimization of systems described by complex mathematical models, as those needed for the emulsion copolymerization kinetics, especially when the computation of the whole molecular weight distribution is included. The proposed approach was applied to the semibatch methylmethacrylate (MMA)/n-butylacrylate (n-BA) emulsion copolymerization, using n-dodecanethiol as chain-transfer agent, and allowed the production of copolymers with constant composition and with well-defined molecular weight distributions.

Modeling particle size distribution (PSD) in emulsion copolymerization reactions in a continuous loop reactor

A detailed dynamic mathematical model that describes the evolution of particle size distributions (PSD) during emulsion copolymerization reactions in a continous loop reactor is developed and compared with experimental data. The model is based on the assumption that two distinct particle populations exist: precusor particles and stable latex particles. Precursor particles are colloidally unstable and therefore may undergo coagulation with other precursors and be absorbed by stable latex particles. It is shown that the kinetic model is able to reproduce the rather complex dynamic behavior of the vinyl acetate/Veova 10 emulsion copolymerization in a continuous loop reactor.