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Polymer Reaction Engineering 08/2006; 10(4)(265–283 (2002)):265-283.
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ABSTRACT: A high solids content n-butyl acrylate/methyl methacrylate emulsion copolymerization process carried out under starved semi-batch conditions was for the first time monitored on-line by means of Fourier transform (FT)-Raman spectroscopy. Partial least squares regression was employed to build calibration models that allowed relating the spectra with solids content (overall conversion), free amounts of both n-butyl acrylate (n-BA) and methyl methacrylate (MMA), and cumulative copolymer composition. In spite of the heterogeneous nature of the polymerization, the similarities of the spectra for MMA, n-BA, and for the copolymer, and the low monomer concentrations in the reactor, the FT-Raman spectroscopy has been shown to be a suitable noninvasive sensor to accurately monitor the process. Therefore, it is well suited for on-line control of all-acrylic polymerization systems.
Applied Spectroscopy 11/2005; 59(10):1270-9. · 1.66 Impact Factor
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ABSTRACT: Fourier transform (FT)-Raman combined with partial least squares regression (PLS-R) calibration models allows the accurate monitoring of solids content, copolymer composition, and free amounts of monomers in starved semi-batch emulsion copolymerizations. The calibration models remain valid as long as the spectrometer and the measuring conditions are unchanged. Unfortunately, maintenance and/or repairing of the spectrometer result in changes in the relative intensities of the peaks of the Raman spectrum, reducing the performance of the calibration models. Therefore, a strategy for the up-date of the PLS-R calibration models is needed. Strategies for calibration model maintenance were assessed, and we found that the best strategy was to build a new model composed of the old PLS-R model plus a PLS-R model able to account for the model mismatch of the old model.
Applied Spectroscopy 11/2005; 59(10):1280-5. · 1.66 Impact Factor
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ABSTRACT: Reaction calorimetry and Raman spectroscopy were simultaneously implemented to monitor high solids content (50 wt %) semibatch emulsion polymerization reactions for two comonomer systems: vinyl acetate/butyl acrylate, VAc/BA, and butyl acrylate/methyl methacrylate, BA/MMA. Overall and instantaneous conversions and free concentration of monomer were measured by means of each technique. It was found that both techniques provided comparable results for the overall conversion, no matter whether the reactions were carried out under starved (BA/MMA) or nonstarved conditions (VAc/BA). However, instantaneous conversion and free monomer concentrations were better estimated by Raman spectroscopy when the polymerization was carried out under starved conditions. Under nonstarved conditions (higher free monomer concentration and lower instantaneous conversions), Raman spectroscopy also provided slightly better estimates.
07/2005;
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ABSTRACT: The kinetics and polymer microstructure of the seeded semibatch emulsion copolymerization of n-BA/MMA were investigated in this work. Free monomer concentration was determined on-line by means of FT-Raman spectrosocopy. The kinetics, gel fraction, and molecular weight distribution were determined for several semibatch reactions of different monomer composition. The experiments show that, when the amount of MMA in the recipe was increased (from 90/10 to 50/50 n-BA/MMA by moles), the instantaneous conversion increased, whereas the gel content decreased and the sol molecular weight exhibited no defined trend. A mathematical model was used to analyze the experimental data.
09/2004;
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ABSTRACT: Fourier Transform Raman spectroscopy was used as an on-line sensor in order to monitor high solids content (50 wt%) n-BA/MMA emulsion copolymerization reactions. Due to the similarity of the chemical structure of the monomers, no separate bands could be detected for each monomer, and therefore a multivariate calibration technique was required (Partial Least Squares Regression, PLSR). Using experimental data from several semi-batch reactions independent PLSR models were built for the solids content, cumulative copolymer composition and unreacted amounts of n-BA and MMA. Those models were experimentally validated by monitoring reactions not used for calibration. It is demonstrated that FT-Raman spectroscopy can be successfully applied to on-line monitor emulsion polymerization reactors. This technique also shows a high potential for process control purposes because independent information about several molecular properties can be obtained from a single apparatus.
Macromolecular Symposia 01/2004; 206(1):135 - 148.
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ABSTRACT: An on-line control strategy to produce copolymer latexes with desired adhesive properties (resistance to shear and resistance
to peel) has been developed. The strategy required a quantitative model relating adhesive properties and molecular weight
distribution that was built using partial least squares regression. The model was used to determine the set-point trajectories
of the monomers and chain transfer agent that are used as manipulated variables in the control strategy. The control strategy
was experimentally verified to produce an n-butyl acrylate/styrene copolymer latex with a resistance to shear of 1310 s and
resistance to peel of 3.1 N/100 mm.
Journal of Coatings Technology and Research 12/2003; 1(1):45-51. · 1.12 Impact Factor
