dyeing and finishing

Dyeing and Finishing

Jenny Zhan, 2013-6-25

Fiber

Cotton: a type of seed hair fiber.

Cotton color: white, cream, gray, brown. It is affected by weather.

Mercerized: treated by caustic to get stronger and improve dimensional stability.

Double mercerized: done in yarn stage and in fabric stage.

Preparation

Bleach: affect fabrics’ strength, color, smell.

Three types of bleach outcome:

-Finish white with optical

-Bleach white for light or pastel shades

-Clean bottom for dark shades

Bleaching agent:

-NaOCl

-NaClO2 (not for spandex. Because it makes spandex yellow)

-H2O2 (eco-friendly)

Optical brightening agents: colorless organic compounds that absolve UV radiation and emit this energy in the visible region. More energy/light is reflected to the observer which makes the object looks brighter.

Dyeing

Dope dyeing: add colored dope when spinning of synthetic fibers to get colored fibers afterward. Purposes of garment dyeing:

-Test the market to decide which color is the most popular, then re-product quickly.

-Some fabrics are thrown away after cutting. It waists less for garment dyeing because the thrown-away has not been dyed.

-But, lower quality. May meet problems if the minor trims on garment are not suitable or affect dyeing.

Indigo: it is in the vat dye family and is insoluble in water and must be solubilized for application. Since its affinity for the cotton fiber is low and as a result offers unique ‘wash-down’ effects. Dyes on the outer surfaces of the yarn leave a white core.

cross-section of yarn

Reserve dyeing防染染色: also can get heather looking, but the real heather is fiber-dyed. Beam dyeing: suitable for the fabric which is sensitive to tension. For eg. light-weight chiffon. Continuous dyeing: pad-dry-pad-steam. First pad dyes, then pad chemistries.

Printing

Heat transfer printing: primarily only for polyester. Heat makes the molecular chain active and sublimation of dyes. Vaporized dyes go into interspaces of molecular chain, then fixing.

Chemical Finishing

Negative impact in chemical finishing: may change shade

Chemical finishing application methods: Use foam, when you only want to add a small amount of additives.

Hand builders硬挺剂: usually for pocket bags, lace

Pre-cure process: pad-dry oven cure-cut and sew

Post-cure process: pad-dry-cut and sew-press-oven cure

Mechanical Finishing

Heat setting: re-denier spandex, make the thickness of fiber more consistency.

Difference between is hair length on the surface:

-Napping (long)

-Brushing (mid)

-Sanding (short)