FAQ in textile dyeing

Here is an amazing site to answer the following ( and many more) frequently asked questions on Dyeing:

Which dyes are more lightfast?

How can I fix non-reactive dyes

Is there anything I can do to "set" the dye on purchased fabric?

How can I dye spandex (or Lycra or elastane)?

How can I dye nylon?

How can I dye rayon?

How can I dye satin or charmeuse?

How can I dye polyester?

What are mordants? What's the difference between mordants and other dye chemicals?

What is soda ash? What's it used for?

What temperature should the soda ash be?

What is the effect of pH? What is the optimal pH?

What is urea for? Is it necessary?

What is the effect of temperature?

Should I use distilled or spring water instead of tap water?

Do I need to use salt?

How are thickeners such as alginate used with dye?

How do you use Silk Salt or other large salt crystals to make bursts of color?

Help! I ruined clothing by spattering bleach. How can I fix it?

How do you "bleach" a screen print on a t-shirt?

Can you tie dye something that is already dark?

How can I neutralize the damaging effects of chlorine bleach?

What chemicals can be used to remove dye?

Which Procion MX dyes discharge the best? Which are good at resisting chlorine bleach?

Which Procion MX dyes are pure, and which are mixtures?

Which MX dyes at one supplier are the same as those at another?

How can I mix Procion MX dyes to get specific colors?

What is in Procion type dye powder?

What other brand names are Procion MX type dyes sold under?

What do the letters and numbers in the code name for a Procion MX type dye mean?

Which Procion MX dyes discharge the best? Which are good at resisting chlorine bleach?

Which Procion H dyes are pure unmixed colors, and which mixtures? How do they compare from one retailer to another?

Which Wash Fast Acid dyes are pure, rather than mixtures?

What are Kiton Levelling Acid Dyes?

My colors just washed out! What happened?

My colors are not very bright. What did I do wrong?

Why are there specks of color all over my fabric?

Why did the thread stay white when I dyed clothing?

How do you tie-dye a star or mandela pattern?

How do you tie-dye a spiral?

How do you tie-dye letters of the alphabet?

How can I tie-dye a peace sign?

How can I dye clothing or fabric in the washing machine?

Can I paint on clothing with oil paints?

Can I screenprint with a dye resist?

How do you tie-dye socks?

Is it safe to eat or breathe fiber reactive dyes?

Which dyes are the safest? Which are the most dangerous?

Aren't natural dyes always safer than synthetic dyes?

Is all-purpose dye safer than fiber reactive dye?

Polyvinyl Chloride- Manufacturing Process and Properties

Polyvinyl Chloride (Vinyon)

Fibre Manufacture:

Vinyl Chloride is the principal raw material from which polyvinyl chloride is made by addition polymerisation. There are two methods commonly used for the production of vinyl chloride:

1. Ethylene+ chlorine--> Ethylene Dichloride--600 deg C--> Vinyl chloride +HCl

or

Cl-CH2-CH2-Cl--300deg C +Charcoal--> Vinyl Chloride + HCl

or

Cl-CH2-CH2-Cl--CH3OH+NaOH (60 deg C)--> vinyl Chloride + NaCl+ H2

2. Acetylene +HCL--150 deg C, HgCl--> CH2=CHCl (Vinyl Chloride)

Polymerisation

the vinyl chloride monomer is polymerised in the emulsion form in an autoclave at a pressure of 50 Atm and at a temperature of 65 deg C. A suspension of the polymer is obtained which is then spray dried.

Spinning

This may be done by dry spinning or wet spinning.

1. Dry Spinning: In the dry spinning process the polymer is dissolved in a mixture of CS2 and acetone, filtered and pumped at 70 deg to 100 deg through spinnerettes into a chamber, provided with heated walls, and into which air is introduced. The solvent evaporating from the extruded filaments is carried away by the air. At the bottom of the chamber the solvent free filaments are removed through a fine orifice and wound on a bobbin. The solvent is recovered and used again. the filaments are stretched to ensure that the molecular chains get oriented and the fibres become stronger and attain less extension at break, increased brightness, transparency etc.

2. Wet Spinning: In the wet spinning process, PVC is dissolved in THF (Tetra Hydro Furon) to give a highly concentrated solution, which is spun into water, through a stretch spinning funnel. The filaments ar stretched and cut into staple fibres.

Properties

1. Tenacity: Wet or Dry: 2.7-3 gpd
2. Elongation at BreaK: Wet or Dry: 12-20 %
3. Moisture Content: 0
4. Specific Gravity: 1.4

v. Effect of Heat: It contracts at temperatures above 78 deg C and shrinks to half its original length at 100 deg C.

vi. It has an excellent resistance to sunlight. It is completely resistant to insects and microorganisms. It is inherently non-flammable.

vii. It is exceptionally resistant to caustic soda, nitric acid and sulphuric acid. It has outstanding resistance to many chemicals including bleaching agents, reducing agents.

Flex Abrasion Resistance- Determination

Method for determination of Flex abrasion resistance:

1. Cut five test specimens each 200mm. long and of 32 or 38mm width depending upon wheter the number of yarns/dm of the specimen is below or above 200. Ravel the specimen to 25 mm in width by removing from each side approximately the same number of yarns. Do not take two specimens fro the weft test from the same warp ends or any two specimens fro the weft test from the same picks. Take weft specimens at wide intervals.

2 After positioning the bar by means of the yoke holder, place the specimen between the pressure (upper) plate and the reciprocating (lower) plate of the apparatus and locate centrally. with the specified folding bar or folding blade inserted, after being clamped and loaded by removal of yoke holder, distribute the tension exerted by the bar or blade uniformly over the width of the specimen and align the long dimension both above and below the bar parallel to the direction of the reciprocating motion. Position the specimen with the fold at the centre of the upper plate, and the reciprocating plate at the rear of its stroke when the specimen is clamped.

3. Load the pressure plate and the folding bar or blade as required by the material specifications. In the absence of the material specification, the bar load sufficient to produce rupture in excess of at least 100 cycles and preferably in 300 cycles should be used, in combination with the lowest head load (pressure) sufficient to prevent vibration of the upper plate at the start of the test.

The ratio of the bar to head loads shall be 4:1

4. Check the bar alignment after the first 25 cycles. If shifting of bar from its normal position is noticed, discard the specimen and make the proper adjustment.

5. Remove the pills of matted fibres debris interfering with proper contact between the specimen and the folding bar or folding blade during the test if they cause a marked vibration of the pressure plate or otherwise interfere with proper abrasion. The pill should be removed by careful clipping. Do not correct the vibration of the pressure plate due to pilling by applying additional load. Check the position of the specimen after additional cycles to ensure that the removal of the pills has not altered the bar alignment.

6. If the specimen slips in the clamps or tension and pressure upon the folded specimen do not remain constant during the test, or an anomalous wear pattern is obtained, discard such individual measurements and test an additional specimen.

7. Before every test the blade is rinsed with degreasing agent.

8. The end point is determined by abrading the specimen until rupture and number of cycles is recorded.

9. The report should include the following information:

a. Abradent used, bar or blade
b. Average number of cycles required to produce rupture the specimen

Total No of cycles Report to the nearest cycle
Below 200 10
200 to 299 25
1000 to 4999 50
5000 and above 100

c. Tension and pressure used.

Acrylic- Manufacturing Process and Properties

Polyacrilonitrile ( Acrylic)

vinyl Cyanide, more commonly known as acrylonitrile, can under go addition polymerisation to form polyacrylonitrile.

Raw Material

Acrilonitrile is the main main raw material for the manufacture of acrylic fibres. It is made by different methods. In one commercial method, hydrogen cyanide is treated with acetylene:

acetylene + Hydrogen cyanide --> Acrilonitrile

2nd Method

Ethylene--Air Oxidation--> Ethylene oxide + HCN--> Ethylene cyanahydrin--Dehydration at 300 deg C (catalyst)--> Acrylonitrile

In a continuous polymerisation process, 95% acrylonitrile and 6% methyl acrylate (400 parts) 0.25% aqueous solution of K2S2O8(600 parts), 0.50 % Na2S2O5 solution ( 600 Parts) and 2N sulphuric acid (2.5 Parts) are fed into the reaction vessel at 52 deg C under nitrogen atmosphere giving a slurry with 67% polymer. The slurry is continuously withdrawn, filtered and washed till it is free from salts and dried.

Acrilonitrile is dry spun. The material is dissolved in dimethyl formamide, the solution contains 10-20 polymers. It is heated and extruded into a heated spinning cell. A heated evaporating medium such as air, nitrogen or steam moves counter current to the travel of filaments and removes the solvent to take it to a recovery unit. The filaments are hot stretched at 100 to 250 C depending on the time of contact in the hot zone, to several times their original length.

Properties of Acrylic Fibres

1. Acrylic has a warm and dry hand like wool. Its density is 1.17 g/cc as compared to 1.32 g/cc of wool. It is about 30% bulkier than wool. It has about 20% greater insulating power than wool.

2. Acrylic has a moisture regain of 1.5-2% at 65% RH and 70 deg F.

3. It has a tenacity of 5 gpd in dry state and 4-8 gpd in wet state.

4. Breaking elongation is 15% ( both states)

5. It has a elastic recovery of 85% after 4% extension when the load is released immediately.

6. It has a good thermal stability. When exposed to temperatures above 175 deg C for prolonged periods some discolouration takes place.

7. Acrylic shrinks by about 1.5% when treated with boiling water for 30 min.

8. It has a good resistance to mineral acids. The resistance to weak alkalies is fairly good, while hot strong alkalies rapidly attack acrylic.

9. Moths, Mildew and insects do not attack Acrylic.

10. It has an outstanding stability towards commonly bleaching agents.

Uses

1. Knit Jersey, Sweater, blankets
2. Wrinkle resistant fabrics.
3. Pile and Fleece fabrics
4. Carpets and rugs.