Single fiber analysis by FTIR microspectroscopy.

摘要

Obtaining excellent spectra from single fibers allows the full analytical capability of infrared spectroscopy to be applied in the textile field and particularly for fiber evidence in forensic science. The capability of an optically efficiency, state-of-the-art, integrated FT-IR microspectrometer (IR{dollar}mu{dollar}s{dollar}sp{lcub}rm TM{rcub}{dollar}, Spectra-Tech, Shelton, CT) was used to produce transmission spectra of single fibers with double apertures 12 {dollar}mu{dollar}m wide by 48 {dollar}mu{dollar}m long. Excellent infrared spectra were obtained from flattened single fiber which were representative of generic fiber groups and showed their chemical compositional characteristics. Single fiber polarized infrared spectra from which dichroic ratios data resulted allowed further distinction among single fibers based on orientation of their macromolecule with respect to the longitudinal fiber axis that was influenced by their manufacturing history. A scheme of individualization of single fibers (with the same chemical composition) based on dichroic ratio data was demonstrated. Surface analysis by ATR infrared microspectroscopy (42 {dollar}mu{dollar}m spot) provided individualization based on the identity of finish or other surface treatment found on a single fiber. Spectral substraction was employed in this work. ATR was also used to analyze bicomponent fibers using spectral subtraction.; With a polarized equipped FT-IR microspectrometer the dichroic ratio of select absorption band of polyester, acrylic and nylon single fibers was measured. Undrawn acrylic and PET single fibers were stretched on the instrument stage and the relationship between dichroic ratio and elongation was revealed for multiple infrared absorption bands. This relationship also was demonstrated from dichroic ratio data of single fibers prestretched by the manufacturers. The potential and protocol for fiber individualization by using polarized infrared spectroscopic data obtained from single PET fibers has been demonstrated. The dichroic ratios were calculated for eight infrared bands from 10 replicates of each of 33 fibers. A two-stage discriminant analysis sorting procedure produced a 100% hits for each of 29 fibers when dichroic ratios of fiber replicates of each single fiber were averaged.