DYEING OF LINENBY PRASHANT KUMARPUNEET ARORA

PROPERTIES OF LINENStrength: two-three times as strong as cotton. It is second in strength to silk.Elasticity: Linen is the least elastic natural fabric.Resilience: Linen is quite stiff and wrinkles easily.Absorbency: The fiber absorbs moisture and dries more quickly. It is excellent for manufacturing towels and handkerchiefs.Heat Conductivity: It is most suitable for use in summers, as the fiber allows the heat to escape, leaving a cool effect.

ADVANTAGES OF LINENLinen fabric is a good conductor of heat.Linen fabric has natural shine with shades of ivory, ecru, tan, or Grey. Linen is never found in pure white color. Linen fabric is crisp and has textured feel ranging from stiff and rough to soft and smooth. Linen fabric is highly absorbent fabric and can rapidly lose water, provided it is manufactured with the right technique. Linen fabric is very durable and strong. Linen fabric is also abrasion resistant as well as resistant to moths and carpet beetles. Linen fabric can be cared for very easily. It naturally resists dirt and stains. It doesn't tend to have lint or pills on its surface too. Linen fabric can be dry cleaned, machine washed or steamed without worrying about any damage to the fabric.

DISADVANTAGES OF LINENLinen clothing can lose its charm if washed with hard water.Linen clothing is restricted to a small range of coloursIt wrinkles and creases easily.Linen clothing is a little more expensive than cotton.

APPLICATIONS OF LINENClothing apparelUpholsteryDraperiesWall coveringsAutomotive end uses

FLAX TO LINENRipplingRettingBreakingScutchingHacklingSpinning

WET PREPARATORY PROCESSESDESIZINGWashed in water bath at 60 65 C for 60 minutes .SCOURINGCHEMICALliquid ratio of 10:1 in a bath containing sodium hydroxide 1.8 g/l. Process conditions: temp. of 98 C, time of 60 minutes; rinsing: temp. of 80 C, time of 10 minutes.

BIO SCOURINGBaths of varying concentration of laccase enzymes from 2.4 to 7.5 U/g fabric in optimal treatment conditions. pH 5.3 (acetate buffer), temperature of 60 C, time 30 - 120 minutes; liquid ratio 10:1. Enzymes inactivation occurred in water bath at a temperature of 98 C for 5 minutes.

BLEACHINGThe bath contains the activation agent and the sodium nitrate (corrosion inhibitor) dissolved in warm water, small amount of 35% hydrogen peroxide (2-5 l per m3 of bath), the 25% sodium chlorite formic acid needed to keep the pH between 3.6 and 4.an optical brightener compatible with the chlorite.

SUMMARYFirst, the sizing agents are stripped in a bath containing a non-foaming wetting agent and the high-temperature desizing enzyme.Step two consists of bleaching without any intermediate washing. It is heated to 95C for 45-60 minutes . The bath is then cooled to 80C, discharged, and the fabric is washed at 95C, then at 65C, the ambient temperature.

MORDANTINGUse 20% Alum to weight of fiber, mix the Alum into the hot water.Use 10% Tartaric acid to weight of fiber. Add it to the hot water mixture.Add the fabric to the hot Alum mixture. Simmer the mordant mixture for about an hour at 90 degrees Celsius.Remove the fabric from the mordant mixture.The Alum mixture can be reused by adding 1/2 the amount of Alum and Tartaric acid as previously .

DYEINGWhen cellulose fiber is immersed in water it develops a negative charge. In order for dyes to show good affinity on cellulose the dyes must be soluble, and have planar, aromatic structures.Solubility is generally achieved via sulfonic acid or other negatively charged groups and the dyes show long-range, come.The use of electrolyte is critical in the dyeing of cellulose. Sodium chloride or sodium sulfate are most often used, although any electrolyte is effective.

DIRECT DYEINGThe simplest way of coloring cellulosic fibers is with direct dyes. Direct dyes provide reasonably bright shades that cover most of the color gamut.

Dye ClassGeneral descriptionMain applicationDirectSimple application; cheap; complete colour range; moderate colour fastness but can be improved by after-treatment with copper salts & cationicfixing agents.Mainly used for cellulosic fibres; can also be applied on rayon, silk & wool.

NATURAL DYEINGMeasure the Sandalwood into a small dish. (200% WOG)Add alcohol to cover and let stand for 30 minues.Place the treated Sandalwood into a heated dyepot .Add clean, premordanted fibre or yarn into the dyepot and simmer for 1 hour. Allow the dyepot to cool.Remove the fibre or yarn, rinse and let dry.

SOME OTHER NATURAL DYES USED

Cochineal Cochineal comes from the crushed bodies of dried insects. Cochineal yields reds, purples, corals and fuchsias, depending on the mordants used.Osage Orange Osage Orange comes from a tree native to Arkansas and Texas. Its wood makes a clear lemon yellow dye.

VAT DYEINGPart 1: The Stock Solution

Dye ClassGeneral descriptionMain applicationVatDifficult to apply (requires reduction treatment to make soluble in water & oxidation to resume insoluble state after dyeing); most expensive;incomplete colour range (strong in blue & green but weak in brilliant red); good all round fastness except indigo & sulphurised vat species; tending to decrease in popularity due to increasing use of reactive dyes.Commonly used for high quality cotton goods, e.g. towel; specially used in the dyeing of denim fabric.

SULPHUR DYEINGIt dyes all cellulose fibres, but particularly linen & jute, to a lustrous & deep black with excellent wash & light fastness.Sulphur dyes are dyed from a dye bath containing Sodium Sulphide & common or Glaubers Salt, & are oxidized by airing or with some oxidizing agents (Sodium Bichromate or Hydrogen Peroxide) in a fresh bath.

Dye ClassGeneral descriptionMain applicationSulphurDifficult to apply (application similar to vat dyes); cheap particularly for dark shade; incomplete black, navy, khaki & colour range (strong in brown but no bright shade); poor washing & rubbing fastness & sensitive to chlorine; may cause fabric rendering of cellulose upon storage (aging).Mostly used for heavy cellulosic goods in dark shades.

GREY FABRIC INSPECTIONFabrics are tested in grey state after weaving and then after finishing processes.In the grey inspection the fabric defects are identified and mended if they aremendable.In the final folding the fabric defects are examined and graded into the following six categories depending upon severity offaults.

1.Fresh or first quality: fabric with no major or objectionable faults.2.Shorter length: piece of cloth having shorter length(less than 50cm).3.Seconds: cloth having minor defects.4.Fents : The cut pieces of cloths measuring 90cm and more but less than 150 cm in length are graded as fents.5.Rags : The cut pieces of cloths larger than 25cm but less than 90 cm are regarded as rags.6.Chindies : These are the cloths having length of 25cm or less

CAUSES OF DYEING DEFECTSThe material is not well prepared for dyeingMaterial having dead fibres or defective fibresLeft over of Chemicals after bleaching etc.Material not properly desizedMaterial not properly mercerised.Absorbancy of the fabric not properSticking of insoluble material on the fibresImpurities are not removed properlyUneven heat treatment.

2. Water Quality not ProperMore Hardness of waterWater has metal ions such as iron.pH of water not properWater having more chlorine 3. Due to Shortcomings in making Dyeing SolutionImproper weight ratio of colors, material and chemicals.Improper material to water ratioImproper filtering of concentrated colors.

4. Due to Shortcomings in the dye machineryComing out of Dye liquor during dyeingDefective instruments controlling temperature, pressure speed etc

DEFECTS IN VAT DYEINGVariation in colour of centre of the fabric with the selvedge. Some of the reasons for this defect are:Improper batching.Non Uniformity in the selvedgeRedyeing of the fabricFoam on the two sides of the jigger.Slippage of the fabric from the roller during dyeing.

Shortcomings in the machine such as malfunctioning of guide roll, expander roller or improper squeezing. Improper filtration of the colours, improper circulation of the liquor during dyeing. Difference in temperature of liquor in the centre and at the ends. Mixing of colours which are not properly compatible. Improper singeing

The remedies of the above defect are are:There should not be any mechanical fault in the machine.Take proper care during dyeing, like filter the colour solution before using Circulate the liquor continuously during dyeing. If some shade is not coming out proper, dye with a slightly heavy shade without taking out the earlier colour.Join the fabrics of the same width while making a lot.

DEFECTS IN SULPHUR DYEINGTenderingSulphur is converted into sulphuric acid after oxidation which is harmful for the linen fibre. This defect can occur on account of not proper washing of the fabric after dyeing which results in retaining of sulphuric acid on the cloth.

2. Uneven Dyeing and Oxidation Marks This may occur due to:Lower strength of sodium sulphideUsing improper amount of sodium sulphide.Na2S does not wash off fully after washing.Variation in temperature.If colours are not dissolved properly. If the chemical used for oxidation is not of good qualityFabrics are not worked upon properly at the time of dyeing.

3. Bronziness This defect normally occurs in heavy shades. Given below are the reasons: More time gap between dyeing and washingUsing more of less strength sodium sulphideUsing more salt.Oxidiser doesn't get washed off properly during washingSodium sulphide doesn't get washed off properly during washing.More presence of iron and copper ions in water.

4. Poor colourfastness to rubbing It depends upon:type of colourLower strength of sodium sulphidePoor absorbency of the fabricFabric is not washed properlyquality of soap used for washing is not properDyeing bath made of iron instead of steelImproper color solution, Improper material to liquor ratio etc.

5. Roughness in FabricIt occurs due to :Using more amount of sodium sulphide that doesn't get washed off during washing.Heavier shadeImproper washingNot using anionic softening agent in finishingNot using wetting agent.

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