On-line monitoring of a latex emulsion polymerization by fiber-optic FT-Raman spectroscopy. Part I: Calibration

The on-line monitoring of a styrene/butadiene latex emulsion polymerization was completed. Our aim was to determine in real time the dry extract perce ntage or the amount of styrene monomer in the reactor. We constructed two p artial least-squares (PLS) calibration models with mean-centered spectra ov er the 3500-2700 boolean OR 1800-500 cm(-1) spectral range. Four factors we re required to model the evolution of the dry extract, and a two-factors mo del calibrated the amount of free styrene. The results were very satisfacto ry: the dry extract was predicted with a root mean squared error of predict ion (RMSEP) lower than 1% over the 2-50% dry extract range, and for the amo unt of styrene monomer, the RMSEP was lower than 5000 ppm over the 0-70 000 ppm range. The nonlinear effects of temperature and water reabsorption wer e considered, and they did not prevent PLS from giving good-quality results .