Fabric Preparation

Singeing

Desizing

Scouring

Bleaching

Mercerizing (Cotton only) , I /

- *

Heat Setting (Synthetics only)

12-2 FaMc Reparalion

Specifications For A Well-Prepared Cotton Fabric

Breaking Strength - 90% of greige strength

Absorbency - 3 seconds or less

Mote Removal - complete

Brightness - 85% of ref. or greater

PH - 6.5 to 9.0

Wax Content - less than 0.3%

Hand - soft and uniform

Fabk Preparation 12-3

Singeing

Definition Passing fabric over open gas flame burners

Pumose Clean fabric surface

Reduce pilling

Problems Singer streaks

Meltballs

Fabric elongation

Carbonspots

12-4 FaMc Preparation

Desizing

Definition Removal of sizing materials from warp yarns of woven fabrics

m e s o fSizes and Removal Methods I. Starch

A. Enzymes (alpha amylases) from 1. bacteria 2. animal pancreases

B. Control 1. pH 2. temperature 3. ions

C. Starch is degraded into small water-soluble fragments

11. Poly (Vinyl Alcohol) or PVA

A. Hot water, detergent, soda ash

B. PVA can be reclaimed by ultrafiltration

111. CarboxyMethylCellulose or CMC

A. Warm water

B. Reclaimed by ultrafiltration

Fabrlc Reparatlon 12-5

Detin it ion Remove Dirt, Grease, Wax and Oil Impurities

!fk.uo T p e s ofsvstems Aqueous (water) Based

Solvent

Problems 0 - Uneven Dyeing, Spots, Blotches

Fastness

Yellowing

Smoke

Redeposition (Polyester)

12-6 Fabric Preparatlon

Contents Of Cotton Fibers After Ginning

Cellulose 95%

Proteins 1.3%

- Hydrolyzed to soluble fragments

Pectic Substances - Soluble in alkaline bath

0.9%

Ash (Ca, Mg, K, Na, phosphates, carbonates) 1.2% . - Soluble in water

OrganicAcids - Soluble in alkaline bath

Wax - Converted to soap

sugars - Soluble

0.8%

0.3%

Other(Dirt) 0.9% - Removed hy suspension or emulsification

Scouring removes residual size and ruptures primary wall to increase absorbency

-- Bleached cotton is > 99% Cellulose

F a k Preparation 12-7

Scouring Of Wool, Silk, And Synthetics

Wool Raw wool contains: - Protein - Dirt - Water - Suint - Grease

Scouring of loose fibers is in bowls * -Soap - Soda ash

Silk Degummed with hot soapy water to remove seracin

Svnthetics Scoured with hot detergent to remove processing oils

12-8 Fubrlc Preparation

Bleaching Systems

Hvdrogen Peroxide (H202)

Cotton, Silk, Wool, Jute, Some Synthetics

Bleach bath contains: - Peroxide - NaOH (pH = 10.5 - 11.0) - Stabilizer - Sequesterant , 1 I

, 0 L '

,

Bleaching is at 95 - 100' C - Steamer 1 - 3 min. - J-Box 1 - 1.5 hr. - Beck or Jig 1 - 1.5 hr.

Sodium HvnochZorite (NaOCZ) Cotton

Bleached bath contains - NaOCl - Alkali + Buffer (pH 9 - 11)

Bleaching is at 40 - 50' C

Requires an antichlor treatment to remove residual NaOCl

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Fabric Preparation 12-9

Mercerization

Pumose Improve dye f in i ty and yield

Improve breaking strength

Improve dimensional stability

Improve chemical reactivity

Improve fabric smoothness

Cover immature cotton fibers

Observable Changes Deconvolution

Lumen disappears

Fibers become more round, smooth, and uniform

Procedure 1. Pad 22 - 25% NaOH at 100% wpu

2. Dwell on cans 30 - 40 seconds

3. Stretch to greige width on chain tenter

4. Wash to < 3% NaOH and release

5. Acid sour, rinse, and dry

--

12-10 Fabrk Preparation

Heatsetting

Definition Applying high temperatures (350 - 400' F) to stabilize fabric

Purpose Establish fabric "memory"

Polyester, Nylon, Triacetate

- Not Rayon, Cotton, or Acrylics

Problems Shade change (before or after dyeing)

Yellowing

Width variation

Excessive moisture in fabric preventing fiber from reaching heatsetting temperatures

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Fabric Preparation 12-1 1