Simultaneous prediction of ethylene content and melt temperature in melt-state polypropylene by near-infrared spectroscopy and chemometrics.

This paper reports on a simultaneous prediction method for ethylene (C(2)) content and the melt temperature in melt state random polypropylene (RPP) and block polypropylene (BPP) by near-infrared (NIR) spectroscopy and chemometrics. The NIR spectra of RPP and BPP in melt states were measured by a FT-NIR on-line monitoring system. The predicted values of the C(2) content from the RPP or BPP spectra measured at 190 and 250 degrees C were investigated using a calibration model for the C(2) content developed by using each RPP or BPP spectra set measured at 230 degrees C. The errors in the predicted values of the C(2) content depended on the pretreatment methods for each calibration model. It was found that a multiplicative signal correction (MSC) is very effective to compensate for the influence of the change of the RPP or BPP sample temperature on the predicted C(2) content. By using modified MSC, it was demonstrated that simultaneous predictions of the C(2) contents and the relative temperature of the melt RPP and BPP from the NIR spectra could be realized.