Knit Dyeing Faults and Remedies

Prepared By : Mazadul Hasan sheshirID: 201000040000813th Batch Wet Processing Technology Email: mazadulhasan@yahoo.comSoutheast University

Southeast University Department Of Textile Engineering

I/A 251,252 Tejgaon Dhaka Bangladesh

Prepared By :

Pretreatment Faults

Oil and grease stains

Causes: 1. Inferior quality of oil used in Knitting2. Excess oiling during knitting3. Inferior quality of detergent used in pre-

treatment4. Poor emulsification in case of excessive oil in

fabric5. Improper washing6. Not maintaining the critical temperature in

respect of emulsification

Remedies: Emulsifiers are used to remove oil and grease stains.

Rope Marks

Causes: When scouring and bleaching the cloth in rope form under high pressure during mangling, folds develop longitudinally.

Remedies: In order to remove the folds, cloth is stentered and in case of severe folds it is mercerized.

Poor Scouring

Causes: When chemical, temperature,PH, time are not properly maintain then this fault is form.

Remedies: Properly control chemical, temperature, PH, time.

Dyeing Faults

Uneven DyeingCauses: 1. Uneven pretreatment (uneven scouring

& bleaching).2. Improper color dosing.3. Using dyes of high fixation property.4. Uneven heat-setting in case of synthetic

fibers.5. Lack of control on dyeing m/c

Remedies: 6. By ensuring even pretreatment.7. By ensuring even heat-setting in case of

synthetic fibers.8. Proper dosing of dyes and chemicals.9. Proper controlling of dyeing m/c

Dye Stains

Causes: •Dark selvedges are caused by non-uniform winding of cloth during dyeing on jiggers. Bronzing effect also appears during dyeing in open jiggers with vat and sulfur dyes.

Remedies: •In case of vat and fast colors cloth should be stripped of color and re-dyed. Boiling leveling bath should be used for direct dyed cloth. Leveling agents should also be added.

Lycra burn

Causes:•Improper mixing of solution.

Remedies: •Proper mixing of solution.

Causes: It refers to color that exactly doesn’t match the standard of the prepared sample.

Remedies: This may be due to faulty dye foundation or application or may be due to variation in dye lot.

Shade Variation

Hole (Dyeing)

Causes:Due to problematic nozzle in dyeing m/c some holes may produce in fabric during dyeing.

Remedies:Nozzles must be cleaned time to time & maintenance should be done properly.

Barre Effect

Causes:Basic difference in the polyester component particularly when using textured filament weft.

Remedies:Take appropriate preventive measure to avoid mix up of weft.

Chemical stains

Chemical spot observed on the fabric.

Color Bleeding

Causes:•It's a loss of color when the dyed fabric is wetted or emerged in water.•The water here, becomes colored and may cause discoloration] of other fabrics.•This is usually due to either improper dye selection or poor dye fastness.

Remedies:•This problem can be minimizing by correct dyes and chemical selection.

Resist Spots

These show as areas where the dyestuff has not taken to the fabricCondensation drips from roofMarks or contamination on padder bowlsFabric wet before dyeingUndissolved chemicalsPoor preparationPoor preparation

Finishing Faults

Moire Effect (Stenter/ Compactor)

Causes:Too high tension during batching and inadequate heat setting.

Remedies:Proper tension during bathing & poor heat setting of fabric prior to dyeing.

Crease Marks (Hydro extractor)

Causes :•Damp fabric moving at high speed in twisted form, in the Hydro extractor (Centrifuge)

Remedies:•Use anti Crease, during the Scouring & the Dyeing process •(The use of anti-Crease, swells the Cellulose & prevents the formation of Crease marks)•Spread the fabric in loose & open form & not in the rope form, in the Hydro Extractor.

Pin Marks ( Stenter )

Poorly adjusted stenter pin

Skewing (Compacting/ Stenter)

Fabric Wales appear in the diagonal direction, to the edges of the fabric, instead of being parallel.

Causes :•Improper feeding of the fabric, while Calendaring & Compacting.Remedies:•Keep a slit line on one side of the tubular fabric. •Use the slit line, as a reference line, to keep the grain lines straight, while feeding the fabric slowly, on the Calendar, or the Compactor machines.

Surface Hairiness & Piling(Tumble Dryer)

Causes :•Abrasion due to the contact with rough surfaces•Excessive surface hairiness caused, due to the abrasive tumbling action(Fabric friction in the Tumble Dryer)•Rough Dyeing process & abrasive machine surfaces (Soft Flow Machine tubes, Tumble Dryer drum etc.)•Reprocessing of the fabric is, also a major cause of piling.Remedies:•Avoid using the Tumble Dryer.•(Control shrinkage by maximum fabric relaxation & over feed in the processing)•Regularly inspect the fabric contact points on all the machines, for any rough & sharp surfaces.

Lustre (Compacting)

Causes :•Physical change in fiber due to local pressure and high temperature on material•Excessive setting

Remedies:•Avoid prolonged contact of stationary material with the hot machine•Select suitable setting temperature

Spirality (Washing)

Spirality appears in the form of a twisted garment, after washing. The seams on both the sides of the garment displace, from their position & appear on the front & back of the garment.

Bowing ( Compacting/ Stenter )

Causes :•Uneven distribution of tensions, across the fabric width while, dyeing or finishing the fabric.

Remedies:•Bowing can be corrected, by reprocessing the fabric, by feeding it from the opposite end. •A special machine (MAHLO) is also available for, correcting the bowing in the knitted fabrics.

Bowing appears as, rows of courses or yarn dyed stripes, forming a bow shape, along the fabric width.

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