The Effect of Ultraviolet Radiation on the Microspectrophotometry (MSP) of Dyed Fibers

As submitted by the proposer:
A common microanalytical technique for forensic fiber characterization and comparison is color analysis through microspectrophotometry (MSP). A microspectrophotometer allows the analyst to non-destructively acquire color information and spectra of small areas of single fibers. The MSP spectrum, resulting from colored dyes and mixtures of colored dyes, can be compared with spectra from the same or other fibers. However, little is known about changes in dyed man-made fibers that result as an effect of environmental conditions, especially exposure to ultraviolet (UV) light over long periods of time. This research will use a microspectrophotometer to study the effect of ultraviolet light on a variety of dyes commonly used to color fibers. Fibers will be monitored and sampled every eight weeks for MSP analysis over an 18-month period of exposure to both artificial UV light in the laboratory (following ASTM G154-12a guidelines) and real sunlight outdoors. Changes in visual color and spectral changes detected and plotted by the microspectrophotometer will be analyzed and evaluated for differences attributed to the photodegradation of the dyes.

Approximately 100 known, colored, textile fabrics will be exposed to UV light for the duration of the study. Fabrics will be selected from a reputable and traceable fiber reference collection (provided by Microtrace LLC), as well as fabric swatches custom dyed to specifications by a textile test materials company (Testfabrics, Inc.). The chosen fibers will represent the most commonly used dyes on man-made synthetic fibers. MSP spectra of UV-exposed fibers will include both the visible and ultraviolet regions for analysis. Spectra will be collected at regular four-week intervals and compared to unexposed (control) spectra. SWGMAT guidelines will be followed when applicable.

This study will provide a fundamental understanding of how ultraviolet light can affect the dyes and color of fiber evidence and improve the discrimination, identification, and individualization of man-made polymer fiber products for the forensic scientist.

Note: This project contains a research and/or development component, as defined in applicable law.

ca/ncf