SCHEME OF VALUATION

Approved by Chairman / Serial No. :

Scrutinising Board with date
________________ Subject Code : P22FTCC21
(Signature with date)

Title of the Paper: ADVANCED TEXTILE WET PROCESSING

PART A – (20 marks)
1. (a) Singeing
2. (c) 5
3. (a) Doctor blade
4. (b) Linen
5. (c) y-axis
6. Saponification
7. Vat
8. Electrostatic
9. Taffeta
10. Yellow/blue value
Answer all Questions (5 x 2 = 10)
11. Bleaching is a chemical process by means of which coloured or discoloured fabrics are made white.
Bleaching should be carried out carefully as the chemical may damage the fabric.
12. Mordant : A mordant or dye fixative is a substance used to set (ie, bind) dyes on fabrics. It does this
by forming a coordination complex with the dye.
13. Thickener- These are high molecular weight compounds giving viscosity to the print paste. It is a
medium for the dye paste to be converted into printing paste.
14. Calendering, tentering, weighting, carbonizing, beetling, glazing, schrenerizing, embossing,
moiering, napping.
15. Yellowness Index is a number calculated from spectrophotometric data that describes the change in
color of a test sample from clear or white to yellow.
PART B – (5 x 5 = 25)
16. (a) The objectives of degumming silk are to improve the silk's color, texture, sheen, and hand, and to
remove soils, oils, fats, and stains:
 Improve silk quality: Degumming removes the sericin, a sticky protein that holds silk strands
together, which improves the silk's color, texture, sheen, and hand.
 Remove stains: Degumming removes soils, oils, fats, and stains.
 Control silk properties: Degumming allows for greater control over the silk's properties, which can
be useful for developing bio-composites.
 Reduce weight: Up to one-third of the silk's weight can be lost during degumming.
 Use degumming waste: Degumming waste liquor can be used to produce sericin powder, which
can be used in cosmetics, hair care products, and as a textile finish.

Or
(b) The sequence of continuous bleaching
 17. (a) Properties of Vat Dyes
 Vat dyes are insoluble in water.
 They are generally converted to their soluble “leuco-state” by means of sodium hydrosulphite
(reducing agent) in the presence of caustic soda.
 Vat dyes have excellent washing and light fastness.
 Vat dyes are very expensive compared with the other classes of dye.
 They are available commercially in different forms such as powder fine, micro-fine, ultra-
disperse, highly concentrated, supra-paste and double-paste.

Or
(b) Natural dyes are colorants derived from plants, animals, minerals, and microbes. They are
becoming more popular as an alternative to synthetic dyes because they are eco-friendly, non-toxic,
and biodegradable. Natural dyes can be extracted from many parts of plants, including roots, leaves,
berries, bark, and wood. Some examples of natural dyes include cochineal, which produces crimson,
scarlet, and pink colors, and purple yam. Natural dyes produce rich colors because they contain
many different pigments. The impurities in natural dyes can create unexpected colors that are
difficult to duplicate with synthetic dyes. Natural dyes are non-carcinogenic and non-allergenic,
making them safer than synthetic dyes. Many natural dyes also have antimicrobial properties.
Natural dyes are biodegradable and don't create harmful waste like synthetic dyes. Natural dyeing is
a complex process that involves scouring and mordenting the fabric to help the dye adhere. After
dyeing, the fabric needs to be washed without soap to allow the dye to set.

18. (a) Rotary screen printing is an advancement of flat bed screen printing. It has cylindrical screens
made of metal foil. One screen makes one repeat of the design. The fabric to be printed is coated with
an adhesive at its back which helps in sticking it to a conveyor printing blanket. The colour comes in
from within the roller. The print paste is automatically pumped from the pressure tanks. Rotaries work
continuously rather than starting and stopping as done in flat screen printing.
Flat screen printing requires a printing table on which the fabric is placed. The screen is placed on
the fabric and held by metal brackets on the sides of the table and the colour is poured on one side of
the screen. There are two operators standing across the screen. First operator presses the colour with
the help of a squeegee and pushes the squeegee till the midpoint. The other operator holds the
squeegee from the midpoint and pulls it towards himself. The screen is lifted manually and placed on
to the unprinted fabric. The first colour has to be dried before the second colour screen is placed on it
to avoid smudging of colour. This is an obsolete method and presently this is done by electronically
controlled automatic machines. A series of flat screens, one of each colour, are set in frames with
automatically operated squeegees and are placed above the belt. As the fabric moves the screens are
lowered automatically and the colour is applied by the squeegees which are automatically regulated.
Or
(b) Blotch printing: In the textile industry, the term “blotch” is referring to designs where there is a
background color behind the printed motifs. Because of the fact that the motifs need to be printed,
normally also the background color is printed. If there were no motifs, the background color would
be dyed.
 Pigment Printing: Printing by the use of pigments instead of dyes. The pigments do not
penetrate the fiber but are affixed to the surface of the fabric by means of synthetic resins which are
cured after application to make them insoluble. The pigments are insoluble, and application is in the
form of water-in-oil or oil-in-water emulsions of pigment pastes and resins. The colors produced are
bright and generally fat except to crocking.

19. (a) Tentering - Tentering is the mechanical straightening and drying of fabrics. This finish follows
any wet treatment. As the fabric leaves the liquid bath, it is stretched between two parallel chains
with pins or clips (this may leave small hole in the selvedge). The chains spread apart to the desired
fabric width, move with the fabric through finishing or drying units, and release the fabric to be
rolled or folded onto cylinders. Fabrics may be tentered several times during finishing and
colouring. This occurs following bleaching, as a part of mercerizing and as a part of the application
of functional finishes. Heat setting of man-made fabrics is frequently combined with tentering.
Products thus processed tend to keep their shape during use and care, and shrinkage becomes
minimal.
Or
(b) These finishes are also sometimes referred to as crease-resistant finishes. Resiliency is the term
used for wrinkle recovery. It has two components one is resistance to deformation and other is
recovery from deformation. Creases are form due to strong mechanical forces. If covalent
crosslinking is not available then wrinkle recovery will be less. Strain energy stored during bending
should be release to get recovery. If covalent bonds are available then strain energy get stored the
bonds gets stretched but they do not get break. So, if then the forces are released, they would like to
recover by releasing that energy which has been stored during bending process. If naturally
intermolecular crosslinks are not available then we have to create them. A crosslinking agent is
needed for creating covalent links. Mainly bifunctional crosslinking agents are used. Polyfunctional
crosslinking agents are generally not used as they can create a three-dimensional network which can
make the fabric stiffer.

20. (a) The working principle of spectrometer :

A spectrometer is a scientific instrument used to analyze the light properties of a luminous
object or reflected light. The instrument measures these properties of light over a specific section of
the electromagnetic spectrum.
The basic function of a spectrometer is to take in light, break it into its spectral components,
digitize the signal as a function of wavelength, and read it out and display it through a computer. The
first step in this process is to direct light through a fiber optic cable into the spectrometer through a
narrow aperture known as an entrance slit. The slit vignettes the light as it enters the spectrometer. In
most spectrometers, the divergent light is then collimated by a concave mirror and directed onto a
grating. The grating then disperses the spectral components of the light at slightly varying angles,
which is then focused by a second concave mirror and imaged onto the detector. Alternatively, a
concave holographic grating can be used to perform all three of these functions simultaneously.
Once the light is imaged onto the detector the photons are then converted into electrons which are
digitized and read out through a USB (or serial port) to a computer. The software then interpolates
the signal based on the number of pixels in the detector and the linear dispersion of the diffraction
grating to create a calibration that enables the data to be plotted as a function of wavelength over the
given spectral range. This data can then be used and manipulated for countless spectroscopic
applications, some of which will be discussed here later on.
Or
(b) The difference between whiteness index and yellowness index-
Yellowness is defined as a measure of the degree to which the color of a surface is shifted from
preferred white (or colorless) towards yellow.
Yellowness, as defined by ASTM E 313, has been applied successfully to a variety of white or
near-white materials, including paints, plastics, and textiles. In terms of colorimeter readings, it was
YI=100(1-B/G) where B and G are respectively amber blue (B) and green (G) colorimeter readings.
 Its derivation assumed that, because of the limitation of the concept to yellow (or blue) colors, it was
necessary to take account of variations in the amber or red colorimeter readings.
Whiteness is defined as a measure of how closely a surface matches the properties of a perfect
reflecting diffuser, i.e. an ideal reflecting surface that neither absorbs nor transmits light, but reflects
it at equal intensities in all directions. For the purposes of this standard, the color of such a surface is
known as preferred white.
ASTM E313 – measuring procedure and settings are described in the same standard (ASTM
E313: whiteness and yellowness of paper) like the Yellowness indices. This method is based on the
use of colorimeter readings B and G. The idea was that chromaticity factor G-B required three times
the weighting of the lightness factor G of the lightness. The equation is: WI=G-4(G-B)=4B-3G
PART C – (3 x 10 = 30)
21. Bleaching: Bleaching is done to remove the natural coloring matters and make the fabric in
required whiteness with minimum damage to fibers, and within the shortest possible time. The main
bleaching agents are Sodium Hypo Chlorite, Sodium Chlorite, Sodium Perborate and Sodium
Percorbonate. Hydrogen peroxide. “Universal bleaching agent.” Almost all textile fibers like,
cotton, silk, wool, polyester/cotton blends are bleached with hydrogen peroxide.
Types of Bleaching:
 Full bleach
 Half bleach
 Sodium Hydrochlorite Bleaching
Mercerization : Mercerization is one of the most important finishing processes of cotton with a
strong caustic
alkaline solution in order to improve the lustre, hand and other properties. It imports gloss to the
fiber, increases its hygroscopicity, strength and improves its dye affinity. Mercerizing process
consists in treatment of cellulosic materials with concentrated solutions of caustic soda at a
temperature of 15 to 18°C.

22. Stages of Dyeing

Dye dispersed in the dye bath

↓↑(Convective diffusion)
Dye in the diffusion layer(boundary layer)
↓↑ (Molecular diffusion)
Dye in the electrical double layer
↓↑ (Adsorption)
Dye absorbed on the fiber surface
↓↑ (Diffusion)
Dye diffused in the fiber
↓↑ (Fixation)

Dye physically or chemically bond in the fiber

The dyeing process is essentially a distribution process. The dye is distributed over at least two phase
systems, the dye bath and textile materials. When equilibrium dyeing is reached, the following
subsidiary equilibrium is established.
1. Dye Dispersed in the Dye Bath: Most of the dyes in solution are in molecular and partially ionized
state or exist in the form of ionic micells.
2. Dye in the Diffusion Layer: When a substrate is brought into a dye bath, a concentration gradient is
created which will-make the dye molecules move or diffuse to the fiber. The dye which approaches the
fiber surface must eventually diffuse through a thin liquid layer, the so-called diffusion layer, towards
or onto the fiber surface.
3. Dye in the Electrical Double Layer: All textile fibers when immersed in water or aqueous solution,
acquire an electrical potential after referred to as Beta potential. At the fiber surface the dye molecules
 must pass the electrical double layer, consists of non-solvated anions (mostly) and solvated cat ions.
These positive and negative ions try to approach the fiber surface as close as possible. This layer is
about 1nm thin.
4. Dye Absorbed on the Fiber Surface: The dye molecules reach the fiber surface (and the first layer of
the fiber). This dye take-up at the fiber surface (absorption) occurs very rapidly and leads to a
reduction of dye molecules in the immediate vicinity of this surface.
5. Dye Diffused in the Fiber: After absorption, dye diffused in the fiber. Owing to the high
temperature, there is always an abundance of dye stuff molecules in the vicinity of the fiber and
agitation has little effect upon the time of half dyeing.
6. Dye Physically or Chemically Bond in the Fiber: The last step of dyeing is fixation. In case
of reactive dyes, the fixation is one-way. Because here dye molecules become attached to the fiber
polymer by strong co-valent bonds. In case of all other dyes this fixation is two ways. Because they are
fixed with fiber by weak hydrogen or salt linkage.

23. Block printing – This is the ancient method of printing designs on the textile material by hand. It
is the simplest of the printing methods. In this method, the desired design is carved on a wooden or
metal block. The wooden block is stamped in the print paste or applied on the surface of the block. The
block is stamped firmly on the selected part of the fabric. Stencil printing - In this type, the design is
first traced on the cardboard, wood, metal or plastic sheets with marker pens or pencils. Using scissors,
knife or sharp blade the design is cut out. The uncut portion represents the part that is to be left
uncoloured. The stencil is placed on the fabric to be printed and the printing paste is applied with stencil
brush through its interstices. Block printing and stencil printing are both techniques for applying color
to a surface to create a design, but they use different tools and methods. Block printing: Uses carved
wooden blocks to apply color in patterns. It's one of the earliest and simplest ways to print on textiles,
and can produce highly artistic results. Block printing styles vary by region and background color.
Stencil printing: Uses a template with cut-out holes to apply color to a surface. Stenciling can be done
on a variety of surfaces, including walls, floors, ceilings, furniture, and fabric. It's similar to screen
printing, but stenciling is generally easier and less expensive. You can use a home printer, cutter, paper,
or cardstock to create stencils.

24. Special finishes applied to fabric -

i. Water-repellent finishes are surface finishes imparting some degree of resistance to water but are
more comfortable to wear because the fabric pores remain open. Such finishes include wax and
resin mixtures, aluminum salts, silicones, and fluoro chemicals.
ii. Flame retardants are used by adding to flammable materials such as textiles to make them hard to
burn or not spread. Flame retardant processing on textile products can minimize damage and save
lives when a fire occurs. For example, curtains, carpets, car seats, sofas, firefighting clothes, etc.
iii. An antimicrobial finish on printed matter is a coating or laminate with antibacterial, antiviral and
antifungal properties. It protects against the growth of microorganisms on the print’s surface so it’s
ideal for hygiene-critical settings or industries whose printed materials are frequently touched by a
high volume of people. Antimicrobial products are key to our health.
iv. The UV protection by textile is a function of the physio-chemical characteristics. The wavelengths
of maximum danger to skin are 305 -310 nm. Therefore, to be able to exhibit effectiveness in
protecting the wearer from solar UV radiation, textiles must have UV protection in the range of
300-320 nm.
v. Wrinkle resistant finishing is a method of coating fabrics with a chemical resin that acts as a cross
linker between hydrogen bonds, enhancing stability and preventing wrinkling. The ability of a
fabric to recover to a specific degree is referred to as crease recovery. Fabrics consisting of
cellulose, regenerated cellulose, and blends containing synthetic fibers have a higher tendency to
wrinkle after washing, tumble drying, and wearing. Today, everyone desires that his or her outfit
would keep its ironed shape. Wrinkle-free coatings give the fabric a silky, wrinkle-free appearance.
Wrinkle-free treatments are widely used in the textile industry to give wrinkle-resistance to
cellulosic materials such as cotton fabric.
25. The functions and working principles of computer colour matching systems :
Computer Colour Matching (CCM) is the instrumental colour formulation based on recipe
calculation using the spectrophotometric properties of dyestuff and fibers. Generally, garment buyer
gives a fabric sample swatch or Pantone number of a specific shade to the garment manufacturer.
Then the manufacturer gives the fabric sample to lab dip development department to match the
shade of the fabric. After getting the sample they analyze the colour of the sample manually. It is a
laborious, time-consuming and critical task and needs skills and expertise of the personnel
developing the lab dip. On the other hand, to save time and money, they can use computer colour
matching system (CCMS).
Functions of Computer Colour Matching System: The following works can be done by using
CCMS –
 Colour match prediction.
 Colour difference calculation.
 Determine metamerism.
 Pass/Fail option.
 Colour fastness rating.
 Cost Comparison.
 Strength evaluation of dyes.
 Whiteness indices.
 Reflectance curve and K/S curve.
 Production of Shade library.
 Colour strength.
The working procedure of CCMS which is used for dyeing lab to match the shade of the products.
Buyer gives a fabric sample swatch or Panton number of a specific shade to the producer. Producer
gives the fabric sample to lab dip development department to match the shade of the fabric. After
getting the sample they analyze the color of the sample manually. In the other hand they can take help
from the computer colour matching system.