Download Investigating how well organic dye molecules attach to natural and

Iida Kojonen
Supervisor: Katariina Yliheikkilä
Investigating how well organic dye
molecules attach to natural and
synthetic fibers, and last on them
Introduction
Natural dyes have been in use for a long
period of time, dating all the way back to
ancient times. They can be classified into
plant-, mushroom-, mineral-, and animalbased dyes depending on where they are
obtained from. The dye that was used for
this investigation was obtained from the
berries of Aronia mitschurinii, which
contains
dye
molecules
called
anthocyanins. Anthocyanins are water
soluble, and the colors that they produce
are very pH-dependent. Natural fibers can
be classified into vegetable fibers, animal
fibers, and mineral fibers. On top of this
there are many synthetic, or man-made
fibers. The fibers that were used for this
investigation are: wool, cotton, linen, and
polyester. That is three natural fibers and
one synthetic fiber. Wool is a protein fiber
(animal fiber), and cotton and linen are
cellulose-based fibers (vegetable fibers).
The purpose of this investigation is to
determine how well natural dyes work in
dyeing natural and synthetic fibers.
Method
All the fabrics were pre-treated before
dyeing. Alum was used for the pretreatment of wool, and tannin and alum
were used for the pre-treatment of cotton,
linen, and polyester. The dye solution was
obtained from the berries by boiling them
in a small amount of water, and then
removing the remains of the berries. The
fabrics were dyed by boiling them in the
dye solution (for wool not bringing the
temperature of the dye solution to a
boiling point). After dyeing all the fabrics
were washed four times to see the final
color of the fabrics.
Figure 1. Dye solution absorption spectra for
all fabrics.
Results
The dye attached to all of the fabrics
well during dyeing and produced
vibrant colors. The color that was
obtained was a purplish pink color.
However, the color does not last on
either the natural nor synthetic fibers.
After washing the colors of cotton,
linen, and polyester were back to almost
the same color they were before dyeing,
with a slight wash of grey, and the color
of wool had changed completely from
what it was after dyeing. Instead of
fading like all of the other fabrics, the
color of wool changed to a greenish
grey color.
Figure 3. The setup for the washing of
fabrics.
Figure 2. The color of cotton before
and after dyeing.
Discussion
From the spectrophotometric analysis of
the dye solutions it can be seen that there
are absorption peaks in the purple and
green areas of the spectrum, which means
that the dye solutions absorbed both green
and purple. This explains why the final
color of wool turned out to be green.
Along with this, the colors produced by
anthocyanins are very pH-dependent, and
produce red/blue colors in acidic
environments and greenish colors in
alkaline environments. The washing
liquid is alkaline, so it could have altered
the color on the fabric.
Figure 4. The berries of Aronia
mitschurinii.