2. Finishing in Textile Industry
Objective –
The objective of giving finishing to textile products
is to give the physical, aesthetic and functional
value, to meet the customer demands. It is
achieved through various process involved namely
bleaching, dyeing (of yarn, fabric or ready-made
garments), coating, printing etc. Mostly it is
combined with a manufacturing process which
gives the final product a required form or shape.
FINISHING:-
Finishing! is the final step in the manufacture of components which require
the highest quality in terms of form, accuracy and surface integrity.Fine-
finishing is an!operation that!adds functionality to!the workpiece
surface!to enhance its!quality characteristics
Finishing technology is used as a final added-value manufacturing process
to obtain a desired surface quality, geometric form and accuracy. It
typically removes a very small amount of material, on the scale of
micrometer or less. Finishing processes often follow previous material-
processing (e.g. casting, forging) and conventional machining
operations(e.g.turning,milling,drilling and grinding).Numerous post-
processes fall under!the general term “finishing”, and sometimes several
of them are used to achieve the!final component quality. As hard-
machining (e.g. hard-turning) is becoming common finishing technology in
the industry,the!finishing technology also often encompasses both
dimensional(accuracy) control and control of surface integrity
(including!surface!texture).
3. FINISHING OF FABRICS
INTRODUCTION
Fabrics as they come out of loom after weaving are called GREIGE GOODS
or GREY GOODS. The grey word denotes to any unfinished product. For
consumer acceptability, they need to be cleaned, improved in appearance
and feel, there special characteristics are to be brought out depending upon
their suitability to the purpose. Therefore they are made to go under certain
processes after coming out of loom or the knitting machine. A broader term
for all these processes is FINISHING
Finishing is treatment given to fabrics which are in the form of grey
good to improve their appearance, feel, serviceability and durability.
It involves cleaning, bleaching, relaxing tensions in the fabric and
straightening the yarns, after all the treatments which modify the properties
of the textiles to meet the needs of the consumer and all the processes
which alter the appearance and performance of the fabric.
OBJECTIVES OF FINISHING
Finishing has the following objectives :
1. To improve the appearance of the material.
2. To increase their weight and stiffness.
3. To improve suitability to the purpose.
4. To improve their utility.
5. To produce variety.
6. To produce imitation.
7. To improve their serviceability.
8. To improve their durability.
CLASSIFICATION OF FINISHING PROCESSES
1. On the basis of their method of application :
(i) Mechanical finishes
(ii) Chemical finishes
2. On the basis of their stability :
(i) Permanent finishes
(ii) Durable finishes
(iii) Semi-durable finishes
(iv) Temporary finishes
3. On the basis of their types :
(i) Aesthetic finishes
(ii) Functional finishes
4. Depending upon their purpose :
(i) Preparatory finishes
(ii) Stabilizing finishes
(iii) Textural finishes
(iv) Functional finishes
6. Finishing techniques are divided into 3 parts
1. Temporary
2. Semi-durable
3. Permanent
TEMPORARY FINISHES FOR TEXTILES:_
Temporary finishes are the type of finish which usually washes away on
washing. The
time period of these finishes is only limited to one or two washes. These
types of
finishes are often carried out by treating the fabric with a paste consisting
of starches
and gum, filling materials, softening agents, wetting agents, glazing agents,
optical
brightener, etc. It is the final fabric feel, properties, etc. upon which the
quantity of
the ingredients will depend on and its construction.
1. Softener is used to impart softening and glazing to the surface of the
fabric. Examples of
softeners are wax emulsion, glaring paste, polyethylene emulsion.
2. For imparting stiffness, body luster starches can be used. E.g. Tapioca,
maize, etc.
3. Wetting agents are used with the paste to wet the fabric quickly for
further finishing. They
are of three types depending on the type of the ionic characteristics of the
mixture.
4. Wetting agent can be also seen in adding weight in the fabric. Examples are
French chalk,
china clay, synthetic softeners. It fills the thick and thin places.
5. Optical brighteners like victoria blue or acid violet are used to add a
slightest bluish tone to
the finished fabric to compensate for the slight yellow tinge of the base
fabric. Chloride salt
absolves the invisible ultraviolet portion of the daylight and gives visible blue
light which
gives a bright and white appearance to the finished material.
7. SEMI-DURABLE FINISHES FOR TEXTILES
Semi-durable finishes are the type of finishes which lasts more in terms
of washing cycle than that
of temporary finishes. The average time period of this washing depends on
the types of finishes
used on the fabric. Some examples of temporary finishes are mentioned
below.
Waterproof finishes are be done using a special type of chemicals which
are most often waxbased. It forms a coating to the fabric like a water-
resistant film and closes the cracks of the cloth.
Substances like rubber, drying oils, etc. are most commonly used. In
recent years synthetic
substances like butyl rubber, synthetic resins, and polyvinyl chloride are
also getting used. The
waterproofing in this fabric depends on the level of coating done on the
fabric. The fabrics can
counter any heavy showers of rain or sudden splashes. After coating, it
makes the fabric
impermeable to air making it unusable in day-to-day apparels. Some of the
common uses are
tents, tarpaulins and wagon cover.
WATER REPELLENT FINISH
It is a type of finish which makes the fabric resistant to water but
maintains the porosity of the
fabric to make it more comfortable.
In water repellent finish, a coating is added to fabrics or garment at the
factory to make them
water-resistant. Water repellent finish is done similar to that of
waterproofing but instead of
coating the entire fabric, the crevices or cracks between the warp and the
weft are left vacant, for
the air and water vapor to pass through the
fabric.
Water repellency of a fabric depends on
several factors namely, nature of the fibers,
yarn structure, fabric porosity, finish applied
and water impact force. Some fabrics made
from cotton easily wet out as compared to
those made from hydrophobic fibers such as
polypropylene.
In this way, hydrophobic properties are achieved by the application of the
water/oil repellent
treatment to the substrates. But they should have some property to
prevent both air and water
passing through them.
8. CHEMICALS OF WATER REPELLENT FINISH
There are various chemicals that can be applied on the fabric to lower
surface free energy of
fabrics than water surface tension to decrease their wetting ability and
increase their water
repellency. Three main types of chemicals are used in water repellent
finishes those are: waxbased repellents, silicone-base repellents and
fluorocarbon-based repellents.
Wax-based repellents are usually the cheapest and the fluorocarbon-based
repellents are usually
the most expensive and the most durable. Wax and silicone-based chemicals
result in water
repellency only, while fluorocarbons result in water as well as oil repellency
in the fabric.
FLUOROCARBON BASED REPELLENTS
Appearance – Milky white to light brown liquid
Ionic – Weak cationic
pH- 2~4
Density (25oC, g/cm3
) - 1.05~1.10
Fluorocarbon (FC) provides fiber surfaces with the lowest surface energies of
the repellents
finishes in use. Both oil and water repellency can be achieved.
FC repellents are synthesized by incorporating perfluoro alkyl groups into
acrylic or urethane
monomers that can then be polymerized to form fabric finishes. The final
polymer, applied to the
fiber, form fabric that presents a dense CF3 outer surface for maximum
repellency. The length of
the per fluorinated side chains should be about 8-10 carbons.
In this way and by appropriate emulsifiers, FC products can be widely
modified for many special
performance profiles. Most FC products are padded, dried and cued. Eat
treatment causes an
orientation of the performance side chain almost crystalline structures.
EXCELLENT WATERPROOFING EFFECTS ON THE FABRICS
IMPART EXCELLENT AIR PERMEABILITY TO THE FABRICS
DO NOT ALTER THE APPEARANCE OF THE FABRICS
LITTLE IMPACT ON THE HAND FEELING OF THE FABRICS
DOES NOT AFFECT THE NONIRON FINISH
ENVIRONMENT FRIENDLY, NON-TOXIC TO HUMAN BEINGS
FEATURES
9. FLAME RETARDANT FINISH
Since burning is a physical process, having a complete flame proof fabric is
very difficult. So, we
slow down the process. Flame retardant role is to slow down the burning
process so that flame
can be controlled to prevent injuries or any loss.
Flame retardant finishes are essential to reduce flame propagation, hence
to achieve flame
retardant properties. The flame-retardant (FR) finishing of fabrics can be
divided into washresistant or non-wash-resistant finishing, depending on
the end-use application. In the case of
garments, FR finishes that are non-durable can be applied to avoid the
constraint in the
application techniques involved. Although these non-durable finishes are
fast to dry-cleaning,
they are not fast to repeated laundering.
By cooling Endothermic processes triggered by the flame retardants cool
the substrate.
By forming a protective layer: The heat transfer is impeded, fewer gases
are evolved, and
the oxygen is excluded.
By dilution: Substances, which evolve inert gases on decomposition, dilute
the fuel in the
solid and gaseous phases. The concentrations of combustible gases fall
under the ignition
limit.
Reaction in the gas phase: The free radical mechanism of combustion
processes which takes place in the gas phase could be interrupted by
flame retardants.
Mechanism of Flame Retardancy
10. TYPES OF FLAME RETARDANTS:
Brominated flame retardants
Chlorinated flame retardants
Phosphorous-containing flame retardants {Phosphate ester such as Tri
phenyl phosphate
Nitrogen-containing flame retardants (i.e. Melamines)
Inorganic flame retardants.
Reaction in the solid phase: One mechanism is the accelerated breakdown of
polymers.
These can be further classified as:
Inorganic, Organo Phosphorous, Halogenated organic and Nitrogen based
compounds.
Halogenated organic flame retardants are further classified as containing
either Chlorine or
Bromine {Brominates Flame Retardants BFR}
The pH of the pad bath should be approximately 5.0. The amount of flame
retardant required
depends primarily on fabric type, application conditions, and test criteria to
be met. Screening
experiments should be conducted to determine the minimum application level
for a fabric.
Application of FR to fabric can be accomplished with conventional padding,
padding with multiple
dips and nips, followed by 30 to 60 seconds dwell gives good results. A critical
factor in the
successful application of precondensate/NH3 flame retardant is control of
fabric moisture before
ammoniation. Generally, moisture levels between 10% and 20% give good
results.
Applications: Used in Fire-fighter uniforms and the areas where there is
chances of getting
exposed to flame or fire.
11. SOIL RELEASE FINISH
A soil release finish does not prevent soil from entering the fabric but it
simply allows it to leave
faster. It removes soil from the fabric and transfers it to the detergent; it
protects the fiber from
attack by soiling matter; it prevents redeposition of soil which has been
dissolved or dispersed
and lastly it prevents dust from being attracted and held by electrical charges
on the fabric
surface.
The composition of this finish is based on acrylic and methacrylic acid and
ester copolymers. An
ester to acid ratio of 70:30 is typical. This ratio provides the proper blend of
hydrophilicity and
oleophobicity (hydrophilic-lipophilic balance, HLB) required for a soil release
finish.
The HLB scale is often used or the pre-selection of surfactants and ranges
from about 0 (very
hydrophobic) to nearly 20(very hydrophilic). For good soiling performance, HLB
values of about 15
are favoured. Greater hydrophilicity would strongly reduce durability to
laundering. The ease of
incorporating different acrylic monomers into copolymers has led to a wide
variety of available
finishes. Other carboxy polymers that have been used as soil-release finishes
include styrenemaleic anhydride copolymers and sodium carboxymethyl
cellulose.
CHEMICAL STRUCTURES
CARBOXY-BASED FINISHES
HYDROXY-BASED FINISHES
One of the earliest soil-release materials was starch, which functioned as a
sacrifial treatment.
Other starch- and cellulose based products that have been used as soil release
agents include
methyl cellulose, ethyl cellulose, hydroxypropyl starch, hydroxyethyl cellulose,
hydroxypropylmethyl cellulose and hydrolyzed cellulose acetates. With some
expectations these
finished lack the laundering durability desired in finish expected to last of a
garment and must be
applied in combination with a binder or cross-linking agent.
12. ETHOXY-BASED FINISHES
ONE IMPORTANT GROUP OF SOIL-RELEASE AGENTS FOR POLYESTER FIBERS IS BASED
ON CONDENSATION
COPOLYMERS OF TEREPHTHALIC ACID WITH ETHYLENE GLYCOL AND POLYETHYLENE
GLYCOL. THE STRUCTURE OF THIS
POLYESTER ETHER COPOLYMER CONTAINS BLOCKS OF POLYETHYLENE TEREPHTHALATE
AND POLYXYETHYLENE
TEREPHTHALATE. THESE PRODUCTS CAN PROVIDE EXTREMELY DURABLE SOIL-RELEASE
PROPERTIES FOR POLYESTER
FABRICS BY EITHER EXHAUST OR PAD APPLICATIONS WITH ABOUT 0.5% SOLIDS ADD-
ON. HIGH SOIL-RELEASE
PERFORMANCE, EXCELLENT SOFTNESS AND COMBINABILITY WITH FLUOROCARBON
FINISHES MAY BE ACHIEVED BY
SPECIAL SILICONE/POLYALKYLENE OXIDE COPOLYMERS.
FLUORINE-BASED FINISHES
These unique polymers have the unusual property of being hydrophobic and
oleophobhic in air
and hydrophilic and oil-releasing during laundering process. This is called
dual-action mechanism.
The hydrophilic blocks are shielded by the fluorocarbon segments when dry,
presenting a
repellent surface.
After immersion in the wash bath, the hydrophilic blocks can swell and
actually reverse the
interfacial characteristics of the surface, yielding the hydrophilic surface
necessary for oily soil
release. Typically, these modified fluoropolymers are pad applied to fabrics in
combination with
the durable press crosslinking agents to increase the durability of the finish.
The higher cost of the fluorochemical soil release agents compared to the
acrylic copolymers is
somewhat compensated by the low add-on required for soil-release
performance. Mixtures of
both polymers types provide a common compromise between efficiency and
costs.
ADVANTAGES OF SOIL RESISTANT
1) It protects the fibre from attack by soiling matter.
2) It prevents redeposition of soil which has been dissolved or dispersed
3) It prevents dust from being attracted and held by the electrical charges on
_the fabric surface.
4) The finish is fast to washing and dry-cleaning.
13. STAIN RELEASE FINISH
Stain resistant fabric technology provides permanent stain repellency and
stain release
properties. It helps garments stay cleaner, longer, because of the dual action
of two robust and
balanced technologies, working in the fabric for the life of your garment.
The stain repellent is applied on the outside of the fabric to allow most
water- and oil-based stains
to roll off.
The release is applied within to prevent ground-in oil-based stains from
remaining in the fabric.
During laundering, the release component pulls water and detergent through
the fabric to wash
out the stain It allows liquid and food-based spills to bead up and be wiped
right off. It allows oilbased stains to be easily released in the wash cycle.
PROPERTIES ACHIEVED BY STAIN RESISTANT
a) Reduces rate of soil absorption, deposit and detention in fabric
b) Provides for good soil release properties
c) Prevents stains from spreading
d) Allows water and spills to form globules on fabric surface preventing
penetration into the fiber
e) Resists water and water born stains
f) Adds soft silicone hand
g) Improves tear strength
ADVANTAGES OF STAIN RESISTANT
1) The Stain resistant treatment does not affect the hand of the fabric.
2) The Stain resistant treatment offers permanent protection to a variety of
knitted and woven
fabrics, including nylon, polyester, cotton, and cotton/poly blends.
CHEMICAL COMBINATIONS
1. USE OF FLUOROCARBONS
A durable stain resistant and soil release finish.
This finish imparts a fabric protector that enables the fabric to repel spills and
stains on contact.
The stain resistant finishes apply a coating to the fibers. This treatment gives
fabric a stiffer hand
as well as some other performance problems.
14. The fluorocarbon stain resistant finish penetrates
the individual fiber, becoming the part of the fiber. The surface properties of
the fabric are not
altered. Liquids can be blotted and soils wiped off and soils released during
laundering.
2. NANOTECHNOLOGY
It involves a chemical treatment of the fabric to create a surface that repels
water and also repels
oil. Most stains come as liquids (like orange juice). The liquid dries up and
develop a stain. If the
liquid can be kept from getting sucked up, a stain can be prevented from
happening.
Using nanotechnology, unique and permanent stain resistant finishes are
being developed.
Nanosize particles can exhibit unexpected properties different from those of
the bulk material.
The basic premise is that properties can dramatically change when a
substances size is reduced to
the nanometer range.
It uses chemistry to make little tiny whiskers and other things that help to
repel liquids.
First the fabric is treated with some acid and some hydrophobic polymers are
pressed into the
fabric. The fabric is then baked to make the whiskers.
APPLICATIONS
High performance active apparel
Work wear
Military
Uniform
Travel apparel
Casual men's and women's sportswear
Wall spaces for hospitality and commercial interior design use--fabrics for
this market are possess
flame retardant and stain release/repel properties.
Nurses scrubs
15. ANTI-MICROBIAL FINISH
Antimicrobial finishing of textile protects users from pathogenic or odour-
generating
microorganisms, which causes medical or hygienic problems. Antimicrobials
control, destroy or
suppress the growth of microorganisms and their negative effects of odour,
staining and
deterioration.
NECESSITY OF ANTIMICROBIAL FINISHES
a) Antimicrobial treatment for textile materials is necessary to fulfil the
following objectives:
b) To control microorganisms
c) To reduce odour from perspiration, stains and other soil on textile material
d)To reduce the risk of cross infection being carried by feet from ward to
ward in hospital
e)To control spread of disease and danger of infection following injury
f)To control the deterioration of textiles particularly fabrics made from
natural fibre caused by
mildew
CHEMICAL COMBINATION
Coagulants, primarily alcohols irreversibly denature the protein structures.
Radical formers like
halogens, isothiazones and peroxo compounds are highly reactive due to the
presence of free
electrons. These compounds virtually react with all organic structures in
particular oxidizing thiols
in amino acids.
One of the most durable type of antimicrobial products is based on a diphenyl
ether (bis-phenyl)
derivative known as either 2, 4, 4'-trichloro-2' hydroxy dipenyl ether or 5-
chloro-2-(2, 4-dichloro
phenoxyl) phenol.
Triclosan products have been used for more
than 25 years in hospitals and personal care
products such as antimicrobial soap,
toothpaste and deodorants. Triclosan
inhibits growth of microorganisms by using
an electro chemical mode of action to
penetrate and disrupt their cell walls.
16. Quaternary ammonium compounds, biguanides, amines and glucoprotamine
show poly cationic,
porous and absorbent properties. Fibres finished with these substances bind
microorganisms to
their cell membrane and disrupt the lipo poly saccharide structure resulting in
the breakdown of
the cell.
Complexing metallic compounds based on metals like cadmium, silver, copper
and mercury cause
inhibition of the active enzyme centers (inhibition of metabolism). Amongst
these, the silver
compounds are very popular and already been used in the preparation of
antimicrobial drinking
water.
Chitosan is an effective natural antimicrobial agent derived from Chitin, a
major component in
crustacean shells. Coatings of Chitosan on conventional fibres appear to be
the more realistic
prospect since; they do not provoke an immunological response. Fibres made
from Chitosan are
also available in the market place.
BENEFITS
Initially, the objective of the finish was to protect textiles from being affected
by microbes
particularly fungi. Uniforms, tents, defence textiles and technical textiles,
such as, geotextiles
have therefore all been finished using antimicrobial agents.
Later, the home textiles, such as, curtains coverings, and bath mats came
with antimicrobial
finish. The application of the finish is now extended to textiles used for
outdoor, healthcare
sector, sports and leisure.
The field of application of the bioactive fibres includes sanitary materials,
dressing materials,
surgical threads, materials for filtration of gases and liquids, air conditioning
and ventilation,
constructional materials, special materials for food industry, pharmaceutical
industry, footwear
industry, clothing industry, automotive industry etc.
The Triclosan when incorporated within a
polymer migrates to the surface, where it is
bound. Because, it is not water-soluble, it does not leach out, and it
continuously inhibits the
growth of bacteria in contact with the surface using barrier or blocking
action.
17. ANTI-STATIC FINISH
Anti-static finishes are chemical substances applied at the textile finishing
mill for the purpose of
reducing or eliminating static. These chemicals are actually substances which
absorb small
amounts of moisture from the atmosphere, thus reducing the dryness of the
fabric.
The garments made purely from hydrophobic fibers such as polyester, have
tendency to develop
static charge, resulting in clinging of garments to the wearer’s body and / or
annoying crackling
sound while wearing on or taking off a garment.
TYPES OF ANTISTATIC FINISHES:
There are two types of Anti-static finish
1. Non-durable finishes
2. Durable finishes
Non-durables finish:
These are used for fiber and yarn processing finishes since ease of
removal is important. The
general requirements for non-durable antistats are:
LOW VOLATILITY
LOW FLAMMABILITY
NON YELLOWING (HEAT STABLE)
NON CORROSIVE
LOW FOAMING
a. Esters of phosphoric acid form the
largest group of non-durable antistats.
Ethoxylated fatty alcohols are also
used to form the esters. The durability
of these phosphoric acid esters
increases with molecular size.
PHOSPHORIC ESTER ANTISTATS
b. Quaternary ammonium compounds are the next
largest group of non-durable antistats
c. The last group of non-durable antistats is composed of non-ionic
compounds such as
ethoxylated fatty esters, alcohol and alkyl amines. Mixtures of cationic and
non-ionic
surfactants demonstrate synergistic antistatic properties.
18. DURABLE FINISH:
The basic principle is to form a cross linked polymer network containing
hydrophilic groups. Polyamines are reacted with polyglycols to make such
structures. These polymers can be formed prior to application to fabrics,
or they can be formed in situ on the fiber surface after pad application.
A variety of cross-linking approaches can be used. One based on
polyepoxides is shown on the right side
PERMANENT FINISHES FOR TEXTILES
Permanent or durable finish as the name indicates is more susceptible to
washes and can
withstand longer time period if not for its lifetime. It is mostly done by
altering with the fiber
properties to minimize the flaws in the fabric be it natural or man-made.
Permanent crease and wrinkle-free treatments:
Wrinkling is one of the most important fabric performance properties. Cotton
fabrics have high
absorption and swelling capacity and are most likely to cause crease. When
textiles like linen and
cotton are laundered, it is desired that wrinkles should be eliminated after the
cleaning and drying
process.
Wrinkle resistant finishing mainly falls into two groups:
A. DEPOSITION TYPE OF RESIN
As the name implies, this finish involves the application of resin to the cloth
as a surface coating.
There will be no reaction between the fiber and the resin in this case. Padding
mangles with acid
catalyst are used to apply them in soluble form to the surface of the cotton
fabric. These resins
provide a lower level of crease resistance than cross linking resins while still
providing stiffness to
the fabric. They include following resins:
PHENOL
FORMALDEHYDE RESIN
UREA FORMALDEHYDE RESIN
ALKYD RESIN
KETONE RESIN
19. B. CROSSLINKING TYPE OF RESIN
Intermolecular crosslinking are created because these crosslinks are
covalent. They will stretch by
during bending but will not break. As result recovery can take place. The
crosslinking agents may
be classified as
Nitrogenous crosslinking agent
Non-nitrogenous crosslinking agent
These type resins chemically react with the fiber and crosslink the fiber
molecules. The type of
finish obtain is durable. They are also known as N-Methylol compounds as the
Methylol groups (-
CH2OH) are attached to the nitrogen. The crosslinking compounds are
commonly called resins, but
the term pre-condensate is correct. Following are some example of
crosslinking agents:
DMU (Dimethylol Urea)
DMEU (Dimethylol Ethylene Urea)
DMDHEU (Dimethylol Di hydroxy Ethylene Urea)
DMPU (Dimethylol Propylene Urea)
TMM (Trimethylol melamine/ melamine formaldehyde)
ADVANTAGES OF WRINKLE RESISTANT FINISHING
1. It improves the crease resistance and crease recovery property.
2. It reduces the shrinkage of the fabric during laundering.
3. It improves resilience, handle and draping qualities.
4. It improves the weight and dimensional stability.
5. It improves the fastness to light and washing of many dyestuffs.
DISADVANTAGES OF WRINKLE RESISTANT FINISHING
Environmental effect-release of free formaldehyde.
Decrease in the tensile strength and tear strength.
Decrease in abrasion resistance.
It gives unpleasant odor.
It gives harsh and stiff feel.
