Defects in Dyeing with Reactive Dyes

Defects in Dyeing with Reactive Dyes

Defect: Colors are not fast to washing, Abrasion;Staining in the fabric when transporting from place to the other, water marks on the fabric

Remedy : Wash the fabric with soap and soda ash at right temperature. Adding sequestering agent will yield good results. Treating with Ammonia will also give good results.

Defects in the fabric due to Printing- Need to take out full color

Remedy: Treat the dyed fabric with Sodium Hydrosuphite with 5-10 gm Sodium Hydrosulphite at 75 deg C for 30-45 minutes. Add 5-7 gms Caustic Soda for even removal of colors. The color becomes light yellow or brown after removal. Wash it thoroughly with soap.

The color can also be removed by solution of Sodium Hypochlorite. Treat the fabric with a sodium hypochlorite solution ( 3-5 gms Chlorine) for 20-30 minutes. Keep the pH between 9-10. The fabric is treated with Acetic acid after removal of color to remove chlorine and to neutralise the fabric.

The fabric can be redyed after removal of color

Defect: Bleeding in colors during washing, abrasion

Remedy: Boil the fabric with caustic, Treat the fabric with Hydrogen Peroxide ( 5-10 gpl, 60-70 deg C) to make the color fast.


Defect: The fabric has been dyed in darker shade, uneven dyeing

Remedy: To take out color from the fabric treat it with caustic for 45-60 min at 70 deg C. Thereafter treat the fabric with 10-20 gpl Acetic Acid for 40-60 min at 80-85 deg C.

Defect: Uneven dyeing, marks of water, marks of colors

Remedy: Wash the fabric in soap and redye in a darker shade

Defect : The fabric has become stiff and rough after dyeing

Remedy: Finish after adding right softner

Defect: Color staining of fabric, uneven dyeing

Remedy: Redye the fabric in darker shade.

Defect: Color staining in fabrics of darker shade, uneven undyeing

Remedy: Dye the fabric in Sulphur black

Caution: Please treat a small length fabric to check the effectiveness and any harmful effects before commencing a full treatment.

Polypropylene Fibres- Manufacturing Process

Polypropylene Fibres

Propylene is one of the constituents obtained from thermal or catalytic cracking of petroleum. Under suitable polymerising conditions, propylene produces fibres forming polypropylene.

Polymerisation: It is done by dissolving propylene in heptane using TiCl3Al(C2H5)3 catalyst system at about 100 deg C under a pressure of 30 Atm for 8 hours. The polymer has a molecular weight of about 80000.

Spinning : Polypropylene is melt spun. The filaments are extruded at 100 deg C above the melting point, cooled in air chamber and collected on bobbins. The filaments are hot drawn (polyethene- cold drawn) and twisted into yarns.


Properties:

1. PP fibres are colorless and have a smooth surface, with round cross section.

2. Tenacity- 4.5-6 gpd
Elongation at Break: 17-20 %
Elastic Properties at 2% extenstion: Instantenous
Stretch for 30 Seconds: 91%, delayed - 9%
Moisture Regain: Nil

3. Boiling water shrinks PP by about 15-20% in 20 minutes

4. Specific Gravity: 0.85-0.92

5. Softening point- 150 deg C, Melting Point: 160-170 deg C

6. PP is also attacked by atmospheric oxygen in presence of sunlight

7. It has excellent resistance to common organic solvents

8. It is resistant to insects and microorganisms

9. PP is generally resistant to common chemicals.

Printing with Natural Dyes

Printing with Natural Dyes

In traditional methods in India, printing is essentially carried in three steps:

1. Preparation of the Cloth
2. Mordanting
3. Dyeing

1. First of all the cloth is prepared by applying tannin.

2. A thickened mordant is printed on this tannin treated cloth in the desired pattern.

3. The cloth is then dyed so that dyestuff attaches itself to those parts of the cloth to which mordant has been applied.

Thus the various processes are:

a. Tanning of fabric
b. printing of mordant
c. fixing of the modant
d. washing out the excess of fixing agent
e. dyeing
f. washing and soaping.

Harda or Myrobalan is used in India as a tanning agent for dyeing and printing with natural colours.

It is applied on scoured cotton fabric in cold ( 10-40 gpl) using conventional method of tub dip wherein the Harda powder is replenished with each piece added to the bath.

After drying various metallic salts such as alum or ferrous sulphate are printed on the fabric either separately or in mixtures.

It is then subsequently dyed with madder root ( Manjith), pometranate rind, kusum flowers and other vegetable dyes.

Trade Names of Natural Dyes

DYE SOURCE	BOTANICAL NAME/ SOURCE	TRADE NAME
Pomegranate	Punica granatium	Pacific
Myrobalan	Terminalia chebula	Kongo
Cutch	Acacia catechu	Thar
Kamala	Mallotus phillipinensis	Basant
Nut Galls	Quercus infectoria	Amber-M
Madder	Rubia cardifolia	Indus
Himalayan Rhubarb	Rheum emodi	Desert
Indigo	Indigofera tinctoria	Nile
Annato	Bixa orellana	Amazon
Lac	Coccus laccae	Rhine-M

You can find a tutorial on How to Use Natural Dyes here.  Receipes for natural dyes can be found here.