In-Situ Real-Time Monitoring of Particle Size, Polymer, and Monomer Contents in Emulsion Polymerization of Methyl Methacrylate by Near Infrared Spectroscopy

This work reports the results of in-situ real-time monitoring of the emulsion polymerization of methyl methacrylate by near infrared spectroscopy (NIRS) under different feed conditions. Besides the monitoring of the monomer and polymer content, the results show that reasonable estimates can be obtained from the spectra for the average particle size of the growing polymer particles present in the reaction medium. This is possible because the presence of the particles affects the spectra (through scattering, diffraction, and other mechanisms). Thus, by using appropriate calibration, it is possible obtain reliable models for particle size, in addition to monitoring the monomer and polymer concentrations. Experimental results for emulsion polymerizations conducted with various feed monomer conditions indicated that, in the spectral range studied, it is not only possible to monitor the evolution of the monomer and polymer contents, but also to follow the changes in the average size of the polymer particle. POLYM. ENG. SCI., 51:2024-2034, 2011. (C) 2011 Society of Plastics Engineers