the experiment indicate an optimal effect of the original pH of
pigment, that is, the dyeing effect was better at pH 4 than at other
pH values.
From the analysis above, optimized conditions for dyeing of flax
fabric with EFCS were obtained: pH 4, 25 g/L salt, 95 C, 50 min, and
25:1 liquor ratio.
The effect of premordanting on dyeing of flax with various
mordants at optimized conditions is shown in Table 7. The K/S value
of the flax fabrics increased in the order mordants
FeSO4 > SnCl2 > none > Al(NO3)3. Varying colorimetric data show
the apparent color change with the kind of mordant. The color of
fabrics treated by premordanting with SnCl2 and FeSO4 was deeper
than that of untreated fabrics. The obvious enhancement in the
color depth is due to the presence of ferrous sulfate, which formed
insoluble metal complexes with flavonoids present in the chestnut
shell pigment. Furthermore, metal complexes present on the fabrics
form an insoluble lake with the reactive group of the fiber,
leading to further fixation of the natural dyes in the fabrics. Additionally,
the color of the fabric treated by premordanting with
cellulase was deeper than that of the untreated one. This effect is
explained by the marked decrease in the cellulose crystallinity after
treatment, which enhances dye penetration.