Friday, January 20, 2012

Problems in Garment Dyeing


With today’s exploding clothing markets of leisure , casual wear and sports wear , garment wet processing has emerged as one of the best production routes towards meeting the quick changing fashion markets.
Unlike fabric or yarn as a substrate , a garment is not a uniform in texture ,it is full of thick places like seams , multilayered sites like pockets , cuffs and shoulders. At times certain unevenness like puckered seams lend a distinct style often highly valued but it could result into rejection of goods at other times .
Here we will try to figure out certain key problems associated with garment dyeing and their possible causes, so that a garment can analyze and overcome these problems. 


Garment size control and appearance

  • variations in yarn size / twist
  • ends per inch
  • picks per inch
  • courses per inch in the knitted fabrics   
Spirality in Knitted Fabrics 
 
  • Twist of the yarn
  • Fibre parameters,
  • Yarn formation system,
  • Yarn geometry,
  • Knit structure
  • Fabric finishing.            
Poor tear strength of garment
  • Degradation of cotton during
  • pretreatment,
  • dyeing and
  • finishing  such as stone /enzyme washing.
Pilling

  • Low twisted yarns.
  • Use of low staple length, cheaper fibre in manufacture of yarns
  • Surface friction of fabrics/garments during wet processing and handling
  • Reworking of  goods
  • Cylinder rotation is too high.
  • Liquor ratio is too low.
  • Excessive cycle time

Puckering of seams during dyeing

  • Improper selection of stitching thread.
  • Due to high twist in sewing thread
  • High residual and wet  shrinkage of sewing threads
  • High stitching tension and improper stitch length..

Poor Rubbing fastness

  • Improper washing and soaping treatment after dyeing.
  • Too much unexhausted dye in dyebath.
  • Loosely held surface indigo dyes
  • Considerable back staining in each step
  • Exposure to atmospheric ozone

Poor light fastness  

  • Use of reactive dyes which are not light fast
  • Use of formaldehyde based dyefixing agents



White, undyed or light seams

  • Use of improper thread such as polyester thread on cotton garments.
  • Use of mercerized thread on unmercerized garments.
  • Mixing of different types of threads such as mercerized and un mercerized .
  • High tension stitching .
  • Unmatched Shrinkage behavior of  garment and thread .
Dullness around Metallic fittings

  • Corrosion and chemical reaction between metallic parts in
  • Pretreatment
  • Bleaching
  • Dyeing
  • Finishing
Streakmarks/ Lines / Creases

  • Overloading of machine
  • Friction between Garments
  • Entanglement of garments.
Shade nonuniformity

  • Differences in fabric preparation processes like
    1. Desizing,
    2. Scouring
    3. Bleaching.
  • Inconsistency in the garment assembly
Poor Dye Yield
  •   Garments contain a finish, softener, or an optical brightener.
  •    Garments were allowed to dry out after pretreatment stage
  •    Liquor ratio is too high.
  •         Agitation is too slow.
  •         Excessive washing between cycles.
  •         Excessive time spent in any cycle.
  •         Too much/too little pretreatment.
  •    Not pretreated for correct time and/or temperature.

Blotchy or Non-Uniformly Dyed Garments

  • Garments contain a finish, softener, or an optical brightener.
  •  Liquor ratio is too low (want 20:1). 
  •  Excessive bath temperature at beginning of pretreat or dye cycle.
  •  Dye bath temperature ramped too quickly .
  •  Improper addition or dilution of dyes/chemicals.
  •  Live steam injection into bath.
  •  Hard water.
  •  Garments not scoured properly
  •  Garments were allowed to dry out after pretreatment stage 
  •  Garments not allowed to wet-out sufficiently before adding pretreatment.
           
Patchy dyeing

  • Starting temperature too high
  • Heating rate too High
  • Salt addition at high temperature
  • Addition of dyes and chemical at once
Spotting

  • Formation of foam
  • Improper washing
  • Machine not clean.
  • Excess pretreat not rinsed from garment before dyeing.
  • Dye not properly diluted or stirred before bath addition.
  • Incompatibility of auxiliaries.

Harshness

  • Insufficient size removal
  • Use of high quantities of alkali
  • Poor softner application
Smell

  • Acetic acid,
  • Residual chlorine,
  • Cationic softners
Back staining

Improper maintenance of
  • pH
  • Temperature

Blotchy / unlevel dyeing in pigment dyeing

  • Improper preparation
  • Higher dosage of cationic reactant
  • High rate of rise in temperature during Cationization
  • Direct contact of steam with garment
  • Too low MLR hence uneven build-up of Cationizer

Batch to batch shade reproducibility in Pigment dyeing
  • Change in pH during cationization

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