A New Method for Fiber Comparison Using Polarized Infrared Microspectroscopy*

Polarized infrared (IR) microspectrometry was used to measure the changes in infrared absorption resulting from the molecular orientation of single textile fibers. Dichroic ratios were determined from single experimental fibers subjected to incremental elongation from an unstretched to a stretched condition. Similar measurements were made on commercial fibers of the same polymer with known draw ratios. These infrared spectroscopic measurements provided a direct means for comparing fibers drawn under production conditions with single fibers stretched in controlled experiments. The dichroic ratio data are indicative of the molecular orientation that occurs when fibers are drawn in the manufacturing process. Dichroic ratio data of commercial fibers can be used to monitor textile fiber quality and to compare fiber evidence in forensic investigations.