FORENSIC ANALYSIS OF ACRYLIC COPOLYMER FIBERS BY INFRARED MICROSCOPY

Ratios of absorbance peak areas (A(C=O)/A(C=N)) of carbonyl and nitril e groups were obtained for single acrylic fibers by IR microscopy. The precision of the comonomer ratios was evaluated for potential applica tion in forensic fiber examinations. Precise (RSDs less than 0.4%) res ults for repetitive analyses of one location on a fiber were obtained. Precision was reduced when the cited ratio was measured at adjacent l ocations along the length of a single fiber. A further deterioration i n precision was observed when different fiber specimens of the same ty pe were analyzed. Analysis of different acrylic fiber specimens of the same type yielded RSDs which ranged from 2 to 6%. Fibers with diamete rs which ranged from 13 to 43 mum were examined. Precision was decreas ed for fibers with smaller diameters. Preliminary results indicate tha t acrylic fibers can differ by manufacturer as indicated by A(C=O)/A(C =N).