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Abstract:
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Major problems have been encountered in the dyeing of
textured woven polyester fabrics. A major portion of the
problem is associated with dye shade differences which
result in a large number of redyes. Both the use of carriers
and high temperature have reduced the shade differences
considerably. This technique has especially helped in rereducing
the shade differences introduced by variations in
the texturing history of yarns.
The purpose of this thesis was to investigate the
variables in dyeing textured wovens and their contribution
to dye shade differences. The variables studied were dyeing
temperature, carrier concentration, pH level, time, and dye
concentration.
The experimental design included the study of
different energy level disperse dyes. Disperse dyes are
classified according to their molecular size, the high
energy dyes being composed of large molecules which are
more difficult to enter the polyester fiber.
The experiment was designed so that all variables
except one were held constant to study the effect of the
isolated variable on color difference.
Color difference was measured by use of a large
sphere I.D.L. Color~Eye. A computerized program was then
used to calculate MacAdam units of color difference. One
MacAdam unit is defined as a just noticeable difference in
color. In addition to MacAdam color difference, KubelkaMunk
functions were measured. The function is described by
two values, K and S, where K is the coefficient of absorption
and S the coefficient of scatter which is written in a ratio
K/S. The function is calculated by the following formula:
K/S = (l-R)^2 / 2R
where, R = reflectance.
S 2R
The K/S value varies linearly with the concentration of dye
on the material.
Several conclusions were drawn from the experimental
studies. The variable temperature on the average produced
significant changes in dye uptake at a change of ten degrees
Celsius below the standard. The color changes produced by
the variable carrier concentration were dependent on the
particular dyestuffs. Certain dyestuff were found to be
more sensitive to changes in pH. The time of dyeing was
found to be significant in causing color changes dependent
on the energy level of the dyestuff. The results of dyeing
with different concentration of dye were random color changes in MacAdam units for the yellow colored dyestuffs. The blue
and red dyestuffs gave unidirectional changes in color that
were directly related to the concentration of dye.
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