In-line monitoring of partial and overall solid concentration during solvent-mediated phase transition using Raman spectroscopy

International audienceA calibration strategy for the continuous monitoring of solvent-mediated phase transition was developed using in situ Raman spectroscopy. Citric acid which exhibits enantiotropy during its anhydrous/monohydrate phase transition was selected as a model organic product. Using 25 samples in suspension, specific calibration of the spectral data was obtained for estimating in-line both the overall solid concentration in suspension and the composition of the solid phase. In addition to such key-measurements, reliable estimates of supersaturation were computed in-line from the mass balance of the solute. In order to validate the technique, anhydrous to monohydrate phase transition experiments were performed in suspensions at 15 degrees C and the kinetic process involved was monitored. Despite the use of various solid concentrations and reactor configurations, both the reproducibility and the reliability of the in situ Raman measurements are shown to be satisfactory

Kinetics and Modeling of Hybrid Core-Shell Nanoparticles Synthesized by Seeded Emulsion (Co)polymerization of Styrene and \upgamma-Methacryloyloxypropyltrimethoxysilane

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Miniemulsion copolymerization of styrene and gama-methacryloxy propyl trimethoxysilane: kinetics and mechanism

International audienceThe kinetics of the miniemulsion copolymerization of styrene (St) and Γ-methacryloxy propyl trimethoxysilane (MPS) was investigated by studying the effects of the MPS/St weight ratio, the nature and amount of initiator, the suspension pH and the surfactant concentration on the overall and individual monomer conversions. It was found that the introduction of MPS accelerates the free radical copolymerization reaction due to its higher propagation rate constant and higher water solubility, compared to styrene. On the other hand, MPS decreases the copolymerization rate mainly during the second half of the reaction. This is presumed to be due to the formation of alkoxysilane-rich copolymers on the particles surface providing a barrier to radical's entry. The rate of hydrolysis is pH-dependent and for a given pH, the influence of the surfactant concentration on the hydrolysis rate suggests that the interface between the latex particles and water is the main locus of hydrolysis. 29Si solid state NMR analysis showed that the hydrolyzed alkoxysilyl moieties did not condense under neutral conditions even for high MPS/St feed ratios. Premature cross-linking could be also minimized under basic conditions but could not be avoided in acidic media

Cocrystallization induced by compressed CO2 as antisolvent: Simulation of a batch process for the estimation of nucleation and growth parameters

A mathematical model describing the GAS antisolvent process applied to cocrystal formation has been developed with the aim of estimating nucleation and growth parameters that are critical issues in crystallization in general. The estimates are obtained by fitting the particle sizes distribution predicted by the model to experimental data. The investigated system was naproxen + nicotinamide that assembled as cocrystals when recrystallized by adding CO2 to acetone solution. The concentration of naproxen + nicotinamide in the liquid phase was calculated from the experimental data of the quaternary system. Particle formation was described by primary and secondary nucleations and a growth rate driven by diffusion. The population balance equation was solved by the standard method of moments assuming a log-normal distribution. Particles of NPX2:NCTA cocrystals of 40-80 mu m mean size were experimentally produced and the experimental size distributions were well fitted by the proposed cocrystallization model. (C) 2014 Elsevier B.V. All rights reserved

Synthesis of Hybrid Core-Shell Nanoparticles by Emulsion (Co)polymerization of Styrene and \upgamma-Methacryloxypropyltrimethoxysilane

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Inline Dielectric Monitoring of MMA/BuA Copolymerization Reactions

Dielectric analysis has become an effective instrumental means for monitoring a variety of polymer resin processing properties. This is because the dielectric properties are sensitive to the changes of resins properties linked to the mobility of the polymer molecules. In the present work, dielectric analysis is used for in-line evaluation of monomer conversion and overall conversion during MMA/BuA solution copolymerization carried out in batch. An empirical model was derived to correlate the dielectric loss factor and monomer conversion. The effects of inhibitor and MMA concentration on the dielectric properties are also investigated. It is shown here that this technique allows the successful real-time evaluation of monomer conversion in lab-scale MMA/BuA solution polymerization reactors, but that limitations do exist, and in particular the need for experiment-specific calibrations