Dyes

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Dyes
Chapter 3 Activity 7
What are they?
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Dyes

• Dyes are organic compounds that can be used to
  impart bright, permanent colors to fabrics.

• Organic compounds are compounds that contain
  carbon.
• Ex C6H12O6 C12H22O11

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History of Dyes

• The earliest records of dyeing processes are from
  the Chinese, dating back to approximately 2600
  BC.

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China Indigo
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India Indigo
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History of Dyes
Until the mid 19th century, all dyes were
obtained from living materials, usually plants.
Processing of cochineal dye (made from beetles)
Certain plants are harvested and dried for their
natural color
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Dried cochineal beetle eggs
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La Cochinilla Starbucks
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Products that contain cochineal beetle extract dye
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The insect produces carminic acid that deters
predation by other insects. Carminic acid,
which occurs as 17-24 of the weight of the dry
insects, can be extracted from the insect's body
and eggs and mixed with aluminum or calcium salts
to make carmine dye (also known as
cochineal). Carmine is today primarily used as
a food colouring and for cosmetics.
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History of Dyes
Modern dyeing now takes advantage of synthetic
dyes that can be specifically made according to
the colors that are desired
The first synthetic dye -- 1856
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History of Dyes-Food Coloring
-Dyes aren't just for fabrics. Colorants have
been added to food for centuries to enhance its
appearance. -Synthetic colorants are currently
approved for use in foods.
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History of Dyes-Food Coloring
-Color is a big factor in what foods we choose
and how much we enjoy a food. -Many food dyes
have been banned through the years because they
were shown to cause cancer. -Currently only 7
FDC dyes are approved in the US. -While some
food colorings are natural, 95 of those used
today are artificial.
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Fabrics

• Cotton Wool
• Natural fibers
• Polymer-Cotton (Cellulose) Wool (Keratin)
• Polyester, Acrylic, Nylon
• Synthetic fibers
• Polymers

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Chemistry of Dyes

• The affinity of a dye for a fabric depends on the
  chemical structure of the dye
• and fabric molecules and on the interactions
  between them.
• Chemical bonding plays an important role in how
  and why dyes work.

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The Chemistry of Synthetic Dyes
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Chemistry of Dyes

• Some dyes require an additional substance
  (usually a metallic salt) to assist in the
  binding of the dye to the fabric. This substance
  is called a MORDANT.
• It prevents the dye from washing out of the
  fabric.

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Chemistry of Dyes

• A dye molecule has to include a part that is
  responsible for the color that you see.
• This is called a CHROMOPHORE

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• White light is made up of ROY G BIV.
• The chromophore will absorb some of the colors of
  light and reflect the rest. The reflected
  color(s) will be seen as the color of the item.
• So, if the chromophore absorbs ROY BIV, then
  you will see the dye as green!

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Color

• We see what is reflected.
• EX A leaf is green because it absorbs all the
  colors but green

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White vs Black

• White is created when all colors are reflected
• TVs add color
• Black is created when all colors are absorbed and
  no color is
• reflected

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Color wheel
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Chemistry of Dyes

• A Second component of a dye is called the
  AUXOCHROME.
• It affects the chromophores ability to absorb
  light energy and thereby affects the color and
  intensity of the dye.

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Colorfastness

• Some dyes have better colorfastness,
• the ability to not run or fade after wearing or
  washing

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Stains

• A stain is a discoloration that can be clearly
  distinguished from the surface, material, or
  medium it is found upon
• Intentional stains (wood stains or paint),
• Indicative stains (food coloring or adding a
  substance to make bacteria visible under a
  microscope)
• Natural stains (such as rust on iron or a patina
  on bronze)
• Accidental stains (like spilling ketchup on your
  shirt).

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Detergents

• Soap molecules contain a hydrophilic (polar)
  head
• and a
• hydrophobic (nonpolar) tail

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Why do we add detergent?

• The hydrophobic tail embeds itself in the stain.
  (agitation cycle)
• The hydrophilic head dissolves in the water and
  washes the stain away (rinse cycle)

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Like Dissolves Like

• Hydrophilic substances like other hydrophilic
  substances
• Hydrophilic (Polar) likes Hydrophilic
  (Polar)Hydrophobic (Nonpolar) likes Hydrophobic
  (Nonpolar)
• Dyes and the fabric need to like each other

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link

• link

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Paper Marbling

• Patterns are floated on a liquid and then
  transferred to an absorbent surface (paper)
• Originated in Japan