Near‐infrared spectra of polyamide 6, poly(vinyl chloride), and polychlorotrifluoroethylene

The near‐infrared spectra (NIR) of polyamide 6 (PA 6), poly(vinyl chloride) (PVC), and polychlorotrifluoroethylene (PCTFE) were measured. The tentative assignment of the overtone and combination frequencies was made with curve fitting calculations and local mode theory. Anharmonicity correction and mechanical frequency were determined from a Birge–Sponer plot. Tentative assignments of stretch overtone frequencies of CH 2 , NH, and CO functional groups of PA 6 and CH 2 , and CH functional groups of PVC were made. Anharmonicity corrections of 55, 61, and 20 cm −1 were obtained for CH 2 , NH, and CO stretch modes of PA 6, respectively, and of 60 and 66 cm −1 for CH 2 and CH stretch modes of PVC, respectively. The local mode model seems to be adequate to interpret the origin of the bands observed in NIR spectra of PA 6 and PVC. Anharmonicity corrections of 33, 19, and 16 cm −1 were obtained, respectively, for CF, asymmetrical CF 2 , and symmetrical CF 2 stretch of PCTFE functional groups. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 199–208, 2002