IN-LINE FIBEROPTIC NEAR-INFRARED SPECTROSCOPY - MONITORING OF RHEOLOGICAL PROPERTIES IN AN EXTRUSION PROCESS - PART I

In-line monitoring of chemical processes is desired for its numerous a dvantages, such as lesser waste, lower developmental cycle time, and l esser costs. In this study, a methodology is presented for estimating polymer rheological properties using fiber-optic near-infrared (NIR) s pectroscopy. Predictive calibration models are developed for simultane ous, in-line monitoring of polymer melt flow index (MI) and comonomer concentration for a system of poly( ethylene vinyl acetate) copolymers . The NIR spectra of flowing, molten poly( ethylene vinyl acetate) (EV A) copolymers are collected in a flow cell attached to a single-screw extruder. Multivariate statistical regression analysis is presented fo r correlation of MI and absorbance in the methylene (C--H) stretch, fi rst overtone NIR wavelength region (1620-1840 nm). Results for simulta neous, real-time monitoring of MI and comonomer composition are discus sed in detail. (C) 1998 John Wiley & Sons, Inc.