Page 164 - Fundamentals of Air Pollution

III. Effects on Fabrics and Dyes 131

fibers, causing them to fail under tension. Cellulose fibers are also weakened
by sulfur dioxide. Cotton, linen, hemp, and rayon are subject to damage
from SO 2 exposure.
Brysson and co-workers (7) conducted a study in St. Louis, Missouri, on
the effects of urban air pollution on the tensile strength of cotton duck
material. Samples were exposed at seven locations for up to 1 year. Figure
9-3 shows the relationship between tensile strength and pollutant exposure.
For two levels of ambient air exposure, the materials exhibited less than
one-half their initial tensile strength when exposed to air pollution for 1
year.
Particulate matter contributes to the soiling of fabrics. The increased
frequency of washing to remove dirt results in more wear on the fabric,
causing it to deteriorate in the cleaning process.
In addition to air pollution damage to fabrics, the dyes used to color
fabrics have been subject to fading caused by exposure to air pollutants.
Since the early 1900s, fading of textile dyes has been a continuing problem.
The composition of dyes has been altered several times to meet demands
of new fabrics and to "solve" the fading problem. Before World War I,
dyes used on wool contained free or substituted amino acid groups, which
were found to be susceptible to exposure to nitrogen dioxide.
When cellulose acetate rayon was introduced in the mid-1920s, old dye
technology was replaced with new chemicals called dispersive dyes. Not
long after their initial use, fading of blue, green, and violet shades began
to be observed in material exposed to nitrogen oxides. The fabric was
marked by a reddening discoloration. Laboratory studies duplicating am-

Fig. 9-3. Effects of sulfation and time on tensile strength of cotton duck. Source: Brysson,
R. ]., Trask, B. J., Upham, J. B., and Booras, S. A. /. Air Pollut. Control Assoc. 17, 294 (1967).