Analysis of EPDM Terpolymers by Near-Infrared Spectroscopy and Multivariate Calibration Methods

Abstract

Near-infrared spectroscopy in the combination, first overtone, and second overtone regions is combined with the multivariate methods of Partial-Least-Squares (PLS) and Classical-Least-Squares (CLS) to provide calibrations for chemical components in ethylene-propylene-diene monomer (EPDM) terpolymers. EPDM samples with 1,4-hexadiene (HD) and ethylidene norbornene (ENB) diene monomers were used for this study. Because unknown interaction effects are present in the spectra of these materials, the PLS calibration method gives more accurate calibrations than the CLS method. PLS coefficient spectra and CLS reconstructed spectra obtained from the calibrations are used to determine the sources of the unknown spectral effects. Results indicate that the combination, first overtone, and second overtone regions of the spectrum can be used to determine ethylene and propylene concentrations in the terpolymers, and the combination region can be used to determine diene concentrations. The presence of intrachain and interchain interactions in the terpolymers is indicated by observation of CLS reconstructed spectra.