Analysis of Near Infrared Spectra during Methyl methacrylate (MMA) Suspension Polymerizations

Abstract

Summary: Near infrared spectroscopy (NIRS) provides means for real-time monitoring of polymerization reactors. Previous experimental studies report successful implementations of NIR-based monitoring techniques for styrene, vinyl chloride and acrylic acid / vinyl acetate suspension polymerizations; however, no information is available in the literature for methyl methacrylate (MMA) polymerizations. For this reason, the main objective of this paper was analyzing the NIR spectra obtained in-line and in situ during MMA suspension polymerizations and observing whether NIR spectra may be used for in-line monitoring and control of the average particle size in these systems. Particularly, NIR spectral responses to changes of the average particle size were analyzed in poly(vinyl chloride), polystyrene and PMMA suspensions, showing that the NIR spectra of distinct reacting systems respond differently to modification of the suspended particle sizes. Finally, it was observed that the control of average particle sizes and particle size distributions in MMA suspension polymerizations requires that control actions be taken at the initial polymerization stages, when monomer conversion is below 30 wt%.

Suspension Copolymerization of Vinyl Acetate and Methyl Methacrylate in the Presence of Amoxicillin

“…By combining vigorous stirring and addition of stabilizer agents, the monomer droplets are maintained in suspension during the polymerization reaction, which takes place in the monomer phase 1, 2. As the polymerization reaction evolves, the dispersed monomer droplets are converted into a more viscous dispersion and then in solid polymer particles 3. Due to several advantages, including the low reaction viscosity and easy recovering of the final product, suspension polymerization process are used to synthesize several important commercial resins, such as polystyrene and styrene copolymers, poly(vinyl chloride), poly(vinyl acetate) (PVAc), and poly(methyl methacrylate) (PMMA) 3, 4…”

Evaluation of Toluene Adsorption by Porous Resins: Batch and Continuous Flow Studies

“…These adsorbents have high stability, high selectivity and easier regeneration compared to other porous materials such as charcoal . Besides these advantages, the synthesis of different polymeric resins enables controlling the morphological characteristics of the material, which can be adjusted according to the contaminant to be adsorbed . Specifically regarding adsorption of BTEX, experimental results show that this type of resin is efficient for adsorption .…”

Miniemulsion Polymerization Monitoring Using Off‐Line Raman Spectroscopy and In‐Line NIR Spectroscopy

“…In special, in hetero geneous polymerization processes, these techniques can be useful to simultaneous monitoring different variables, such as those related to chemical changes in the reaction medium (e.g., monomer conversion) as well as those related to the physical changes in the particles (e.g., changes in particle size). [8][9][10][11][12][13][14][15][16][17][18][19] Spectroscopy-based sensors in combination with optical fibers allow the inline measurements and real-time monitoring of polymerization processes. [18][19][20][21][22][23][24][25][26][27][28][29] For the particular case of heterogeneous polymerization reactions, Raman and NIR spectra show two distinct regions, as identified in Figure 1, where different characteristics can be explored: (a) the spectral region that permits to identify chemical information related to the vibrations of the main bonds present in the components (monomer and polymer) and (b) the spectral region with physical information, where the spectrum baseline variation is related to physical properties, such as particle diameter in this case.…”