DYEING FABRICS

How Dyes Attach Themselves to Fabric

Different dyes are required to color different groups on the fibers….

Acidic Dyes

Contain acid groups that form attractions to –NH groups Used in wool, silk and nylon

Direct Dyes

Bond to fabrics by hydrogen bonding In fabrics such as rayon and cotton

Fabric Reactive Dyes

Used for wool at first but it didn’t work The dye was then used on cotton which

did not damage fibers Dye molecules react with amine and

hydroxyl group on the cotton fibers

Color Fastness

Definition: The property of a pigment or dye to keep its original hue without fading, running, or changing

Different dyes will have different fastness rates depending on what fabric they are applied to

Also certain dyes only work on certain fabrics

Something that works on leather wont work on cotton

Running

Occurs when you wash fabric or when you expose something to a detergent

Occurs also when the dye has a weak attraction to the material it’s attached to

Fading

Caused by the chemical change of unstable dye molecules to a less strongly colored form

Things that cause fading: Sunlight UV radiation Oxygen and atmospheric water

No way to stop a fabric from fading

Dyes Today

Built to be strongly bonded to the fabric they are attached to

This way they wont run as easily or fade as easily

Also, over the years scientists have learned what dye works well with what fabric