In-line monitoring of partially miscible molten polymer blends

High quality products, lower costs, reduction in waste, and improved profitability are important concerns of industries in plastics manufacturing. In-situ or in-line monitoring of flowing molten polymers by fiber optic near infrared (NIR) spectroscopy offers all these advantages along with ease of handling molten polymers during the manufacture of plastics. The objective of this research is to demonstrate the viability of using NIR spectroscopy coupled with fiber optics, for in-line composition monitoring of partially miscible polymer blends. Studies on blends of styrene-acrylonitrile (SAN)/acrylonitrile-butadiene- styrene (ABS), SAN/polycarbonate (PC), and PC/ABS were performed. Absorbance data for the molten blends was recorded in the NIR region from 1200 nm to 2400 nm. Multivariate analysis by partial least squares (PLS) and principal component regression (PGR) of the spectroscopic data was carried out to develop robust calibration models, which were subsequently used for predicting the composition of unknown samples of the polymer blends. For the partially miscible blend systems, qualitative and quantitative interpretation of loadings and scores showed meaningful contributions from the first three factors for ABS/SAN and SAN/PC blends and from the first two factors for PC/ABS blends. Standard errors of calibration (SEC) and standard error of prediction (SEP) values were also calculated based on the optimal number of factors for the calibration and prediction sets, respectively.