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Dyeing & Printing || Differences Between Dyeing And Printing

Dyeing and printing are the two major wet processing techniques for coloration of fabric. In the dyeing process; only one color is produced but in the printing process; various types of colored design are produced on the fabric surface. Dyeing is done on grey fabric but printing could be done on both pre-treated fabric and colored fabric.

Difference Between Dyeing And Printing: There is a lot of difference between dyeing and printing process. Here, I have mentioned some major difference between dyeing and printing.

Dyeing Printing
1. By the dyeing process, dyes are applied on the whole fabric equally. 1. By the printing process, dyes are applied on the fabric localizedly to produce desired design.
2. Fabric, yarn and fibers are dyed by dyeing. 2. Generally printing is done on fabric.
3. In a dyeing process, dyes are applied on the both sides of the fabric. 3. Dyes are applied on olnly one side of the fabric.
4. No precise design is required for dyeing. 4. Design is must for printing.
5. In a dyeing process, only one dye is used. 5. In a printing process, one or more dye is used.
6. Precise temperature is required for dyeing. 6. In printing, it is not necessary to maintain precise temperature.
7. Thickener is not required for dyeing. 7. Thickener is must for printing paste preparation.
8. The density of dye solution is less than the density of printing paste. 8. In printing, the density of printing paste is higher than dye solution density.
9. Huge amount of water is required for dyeing. 9. Small amount of water is required for printing.
10. Steaming or curing is not necessary for dyeing. 10. Steaming or curing is must for printing to fix the dyes or pigments on the surface of the fabric.
11. Dyeing is comparatively cheaper than printing. 11. Printing is costly than dyeing.
12. Dyed fabrics are soft. 12. Printed fabrics are hard and harsh.

Process Flow Chart of Dyeing Textile Materials | Basic Structure of Wet Processing Technology

Wet processing technology and its uses are huge in textile sector. Dyeing process for different textile materials could be different but its basic idea is same for all. For all types of dyeing pre-treatment is must for removing unwanted materials from textile materials. Pre-treatment style differs for the shade of dyed materials. Shade may be light or deep. Also these pre-treatment depends on buyer’s requirement. After pre-treatment textile materials are ready for dyeing. After dyeing after-treatment is necessary for get the final finished products. At last, that’s product becomes ready to use. This sequence can be expressed by a flow chart.

Basic Flow chart of dyeing textile materials is like the followings:

Grey Textile Materials (Fiber, Yarn or fabric)

Singeing

Desizing

Scouring

Bleaching

Mercerizing

DYEING/PRINTING

Finishing

Marketing

Now I like to discuss shortly about the different terms of the flow chat. Here, grey textile materials are fiber, yarn or fabric which is also consider as the raw materials for dyeing.

Singeing is the first steps of pre-treatment. The process by which loose, hairy and projecting fibers are removed is called Singeing.

Desizing is the second steps of pre-treatment. By this process gummy materials are removed. Also size materials removed by this process.

Scouring is the third steps of pre-treatment. This process is performed for removing impurities of the textile materials.

Bleaching is another important step which is used to reduce natural color of the raw materials. Dyeing performance depends on it much more.

Mercerizing is the special types of treatment. It performs if buyer wants. It is an additional treatment. It increases the strength and luster of the materials.

Dyeing is the main process where a white material becomes decorated by different colors. We have to know about the depth of shade of the materials.

Printing is called as localized dyeing. Different types of printing are done for giving special appearance on colored or white fabric.

Finishing is the last treatment of wet processing. Different types of properties can be added to the materials by different finishing effects.

Marketing is our main goal. Say, if we done everything but there have no buyer then everything is waste. So we should have a strong marketing department.

So, all of this is about flow chart of Dyeing.

 

Mercerizing | Definition-Mechanism and effects of Mercerizing

Mercerizing is one of part of wet processing technology. Mercerizing is the special type of treatment. Mercerizing is done for get some special properties of the textile materials. By the mercerizing process the physical properties of the material changes. After scouring and bleaching process, mercerization is done.

 

 

Mercerizing is the process of subjecting a vegetable fiber to the action of a fairly concentrated solution of a strong base (Sodium hydroxide 50-70 deg Tw and 18 degree Celsius temperature) so as to produce great swelling with resultant changes in the fiber structure, dimensions, morphology and mechanical properties.

Mechanism of Mercerizing: We know that fiber cell structure is different from one to another. Some cell structure is triangular, some are oval, some are hexagonal, and some are zigzag and many more. When light falls on that cell it reflects the light as per its cell structure. Sometime this reflection is regular, some time it is not. It affects the luster of the fabric surface. For getting a regular reflection from the fiber it pass through a process called mercerizing process.

By mercerizing process the strength of the fiber increases up to 20-30%. Cotton fiber’s shape become round when it shrink in the solution of caustic soda (NaOH). The lumen becomes small and the cell wall become greater for this reason, strength of the fiber increased. The surface of the fabric become fine and light reflects on it constantly; so the luster of the fabric increase, the swelling power of the fiber also increase. Generally low twisted yarn is suitable for mercerizing. Mercerized fabric is more suitable for dyeing and printing than the bleached fabric.

Effects of mercerizing: Different types of changes are occurred for mercerizing in the cotton fabric. Following changes are the most important:

  1. Shrinkage in the area of the fabric.
  2. Tensile strength of the fabric increases.
  3. Fabric luster also increases.
  4. Hygroscopicity of the fabric increases.
  5. Capability for absorbing dyes increases.
  6. Preferential absorption of sodium hydroxide during the treatment.
  7.  Mercerizing increased action of lower temperature.
  8. Possible compound formation soda cellulose.

Luster of the fabric is the most vital point. Attraction of the fabric depends on the luster of the fabric. Luster of fabric depends on various factors. They are as follows:

  1. Cross-section of the fiber.
  2. Staple length of the fiber.
  3. Wall thickness of the fiber.
  4. Concentration of Sodium hydroxide.
  5. Temperature of the mercerizing solution.
  6. Percent stretch.
  7. Yarn construction.
  8. Yarn twist.
  9. Doubling of yarn.
  10. Degree of singeing.
  11. Application of tension.
  12. Rate of drying.

Mercerizing increases the luster and strength of the fabric. Generally mercerizing is done for cotton. Mercerizing depends on the requirement of buyer. The price of the mercerized fabric is higher than bleached fabric.