Ratios of absorbance peak areas (<i>A</i><sub>C=O</sub>/<i>A</i><sub>C≡N</sub>) of carbonyl and nitrile groups were obtained for single acrylic fibers by IR microscopy. The precision of the comonomer ratios was evaluated for potential application in forensic fiber examinations. Precise (RSDs less than 0.4%) results for repetitive analyses of one location on a fiber were obtained. Precision was reduced when the cited ratio was measured at adjacent locations along the length of a single fiber. A further deterioration in precision was observed when different fiber specimens of the same type were analyzed. Analysis of different acrylic fiber specimens of the same type yielded RSDs which ranged from 2 to 6%. Fibers with diameters which ranged from 13 to 43 μm were examined. Precision was decreased for fibers with smaller diameters. Preliminary results indicate that acrylic fibers can differ by manufacturer as indicated by <i>A</i><sub>C=O</sub>/<i>A</i><sub>C≡N</sub>.
Mary W. Tungol, Edward G. Bartick, and Akbar Montaser, "Forensic Analysis of Acrylic Copolymer Fibers by Infrared Microscopy," Appl. Spectrosc. 47, 1655-1658 (1993)