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

In an extrusion process, linear viscoelastic properties of molten poly ( ethylene vinyl acetate) (EVA) copolymers, which have one principal f actor of variation, can be estimated from in-line near-infrared (NIR) spectra. The NIR transmission spectra of molten polymer flow stream we re collected in a flow cell attached to a single-screw extruder. Dynam ic rheological functions obtained from linear viscoelastic measurement s, for example, the complex viscosity response, are regressed against the NIR spectra. The primary method for the rheological measurements i nvolved sinusoidal, oscillatory shear experiments at varying angular f requencies using a cone-and-plate viscometer. All measurements were ca rried out on molten EVA polymers at 200 degrees C. Calibration models were built on spectra in the carbon--hydrogen (C--H) vibrational stret ch, first overtone, wavelength region (1620-1840 nm), and these models were used to predict the rheological material functions of copolymer samples. The robustness of these models was tested on independent pred iction samples that had not been included in the calibration models. ( C) 1998 John Wiley & Sons, Inc.