UNDER THE GUIDANCE OF
Prof. (Dr.) M.D.TELI
Omkar S. Parmaj
Research scholar in
Institute of chemical technology Mumbai
Coating has now become a very important technique for adding value to
Coating enhances and extends the range of functional performance
properties of textiles.
The use of these techniques is growing rapidly as the applications for
technical textile material has become more diverse.
The key to success in textile coating and lamination depends upon the
application of appropriate technology using advanced machinery.
Coating is an application of an appropriate chemical system to
form a layer of a coating compound on the substrate.
Coating is a process in which a polymeric layer is applied
directly on one or both the surfaces of the fabric.
Depending upon the end-use, heavy-duty technical textile
coatings may be applied.
Unlike woven textile materials now coating is being done on
other textile substrates also such as warp-knitted, weft-knitted
Formulation contain a wide range of chemicals
depending upon :
Nature of polymer
Necessary additives for the specific end-use.
Whether coating has to be foamed prior to
Type of coating machinery to be used.
PHYSICAL FORMS OF
Solvent based systems
Waterbased systems-dispersions and emulsions.
100% solids materials -Film, Powder, Hot Melt.
Process flow diagram of coating
A wide range of textile materials is used as substrates for coated fabrics.
Cotton, Rayon, Nylon, Polyester and blends such as of polyester with
cotton or rayon are used as substrate.
Polyester is the most popular in staple form for nonwoven material and
also in spun form for woven material.
Polypropylene is emerging as the fibre of choice because of its low
specific gravity, strength properties, chemically inert nature and low cost.
SELECTION OF FABRIC
The following aspects need to be considered:
Strength and modulus
Resistance to acids and chemicals
Resistance to microbiological attack
Environment of use
PARAMETERS for uniform
• The parameters necessary for uniformity in coating add-on are as
Viscosity of the coating material
Substrate uniformity and porosity
Any variation in these parameters may lead to a non uniform
The coating range is limited to about 0.02 to 0.5 mm thickness.
METHODS OF APPLICATIONS
The technique that is selected for any given product will be
dependent upon a number of factors such as:
The nature of the compound to be applied in terms of its
viscosity and other physical characteristics.
The degree of penetration required into the substrate.
Cost that can be accepted in the end-product.
Foamed And Crushed Foam
Hot Melt Extrusion Coating
Rotary Screen Coating
Dry Powder Coating
Slot Die Or Extrusion Coating
Mayer Rod Coating
Kiss Roll Coating
Gravure Roll Coating
Reverse Roll Coaters
Direct application of coating fluid is done on to the textile fabric by
uniform spreading of coating by the means of a fixed knife.
The gap between the bottom of the knife and the top of the fabric
controls the thickness of the coating.
The main techniques used are as follows:
Knife on air
Knife over roller
Direct coating uniformity depend upon:
Shape of knife
Angle of knife to fabric
Position of knife
This type of knife coating is a blade over air, or floating knife
The knife is fixed above the substrate.
The doctor blade presses the upper surface of the substrate and
forces the coating layer to penetrate into the substrate.
The amount of coating applied is controlled by fabric tension
and depression of the knife .
The sharpness of the blade, alignment angle and degree of
depression into the substrate influence the amount of coating
KNIFE ON ROLLER
In this process knife blade is suspended above a roller.
The roller can be steel or rubber coated.
The knife does not touch the substrate directly and there
is a gap between substrate and knife which controls the
thickness of the coating.
FOAMED AND CRUSHED FOAM COATING
The method can apply polymer to Woven fabrics, Knitted
fabrics, fabric produced from spun yarns or fabrics of an
open construction which cannot generally be direct coated.
Fabrics of a general open construction which cannot
generally be directly coated.
Foam, which is rather like shaving cream, sits on the top of
fabric and Crushed by roller and coat the fabric.
Fabric become much softer handles and better drape than
can generally produced by direct coating.
Application: Apparel goods, floor coverings, wall coverings
,black-out curtains and curtain linings .
The principle of transfer coating is first to spread the polymer on to
release paper to form a film and then to laminate this film to the
fabric. The process is divided in few steps such as:
Coat the resin (which will become the top layer) on to the
transfer paper and evaporate off the solvent.
Coat on the second layer, which will become the base layer (and
is actually the adhesive which joins the top layer to the fabric).
Lay the fabric on top of the coating, nip together, evaporate the
solvent and crosslink the two layers together.
Peel the coated fabric off the release paper.
Application: footwear, gloves and waterproof mattress covers.
Woven velvet automotive seat fabric,
This method is used for thermoplastic polymers such as
polyurethane, Polyolefins and PVC.
These are applied by feeding granules of the material into
the nip between moving heated rollers.
This method can apply resin (in the form of films) to fabric at
a faster rate than that can be achieved by transfer coating or
This process is used to produce light weight coverings or
Calenders are primarily used to produce unsupported films of PVC and
rubbers from compounded polymer ‘dough’.
This process can also be adapted to apply freshly produced film to fabric.
Calenders consist of a number of massive rollers.
Rollers rotate to crush the ‘dough’ and smooth it into films of uniform
The thickness of the film is determined by the gap separation of the rollers.
The more rollers, film produced is more accurate.
ROTARY SCREEN COATING
The rotary screen technique applies to a fabric by forcing
it through a cylindrical screen, it is used mainly for textile
The technique can also be used for coating polymer onto
fabric with add-ons in between 5 and 500 g/m2.
The add-on is controlled by :
Mesh of the cylindrical screen,
Pressure of the squeegee bar inside Screen .
A coating material can be sprayed directly onto the
Spray coating methods are:
Pressed air vaporization,
Airless pressure spray,
Hot vapour impelled spray ,
Electrostatic spray and
Dry powder resin spray.
The most common method is compressed air
vaporization, where air and coating materials are pressed
out through a nozzle.
Lack of uniformity and precision of application
Occasional blocking of spray nozzle
Fig: Spray coating
DRY POWDER COATING
There are two processes in this category,
1. scatter coating and, 2. dot coating.
These processes are used for coating fusible polymer powder i.e , polyethylene,
polyamide, polyester, and Ethylene-vinyl acetate (EVA).
The products are used for fusible interlinings, carpet backcoating, especially in
the automotive industry for contoured car carpets, and for lamination.
Scatter coating process, polymer powder of 20–200 µm size is spread uniformly
onto a moving textile substrate. The web is then passed through a fusion oven and
calendered. The coating weight is dependent on feed rate and web speed.
Powder dot coating process, a heated web having a surface temperature slightly
less than the melting point of the polymer is brought in contact with an engraved
roller embedded with dry powder. The web is thus coated with a tacky polymer
powder in a pattern dependent on the engraving. The engraved roller is kept cool to
prevent the polymer from sticking to the roll.
In curtain coating the coating fluid forms a freely falling liquid
sheet and is deposited onto a moving substrate as shown in figure.
No friction is involved so the coating fluid is not forced to
penetrate the substrate structure but follows its surface to form a
This method is capable of producing a thin film with a range of
few microns and the film thickness is not affected by substrate
Preventing air entrapment and establishing stable fluid curtains are
the keys to achieving quality curtain coating.
SLOT DIE OR EXTRUSION COATING
In this method plasticized coating compound is pressed
through a sheeting die and transferred directly onto the
substrate to be coated.
In the traditional slot die coating system the die lip is
in contact with the substrate and backed by the roller
which imparts pressure on the substrate.
This is called a closed system, where there is no
contact between the coating materials and the air.
MAYER ROD COATING
In this method, compound is applied
on the web by a single-roll
The coating is post-metered by a
wire wound rod, known as the Mayer
rod that removes excess coating.
An excess of the coating is deposited
onto the substrate as it passes over
the bath roller.
The wire-wound metering rod,
sometimes known as a Meyer Rod,
allows the desired quantity of the
coating to remain on the substrate.
The quantity is determined by the
diameter of the wire used on the rod.
KISS ROLL COATING
The coating is applied on the web as it touches
the nip-to-nip of the applicator roll.
The pickup roll may be rubber covered, and
the applicator roll made of steel.
The metering is done by nip pressure, and
consequently, the amount of material coated on
the web is dependent on nip pressure, speed of
the operation, roll hardness, and its finish.
GRAVURE ROLL COATING
Engraved dots or lines of the
engraved roller fill with the
The excess coating wiped off
by the Doctor Blade.
The coating deposited onto
the substrate as it passes
between the Engraved roller
and a Pressure Roller.
REVERSE ROLL COATERS
The coating material is measured onto the applicator
roller by precision setting of the gap between the
upper metering roller and the application roller below
The coating is 'wiped' off the application roller by the
substrate as it passes around the support roller at the
4-roll versions are more common than 3 roll versions.
ADVANCED COATING POLYMER
In today’s era the requirements of human beings has been
totally changed , so research is going on to achieve human
Some of such achievements are phase change coatings,
conductive coating, anti- bacterial coating etc.
After all introduction of nanotechnology has changed the
thinking. Some of those are discussed below.
ATMOSPHERIC PRESSURE PLASMA COATING
Water-repellent and self-cleaning coatings can be produced with
the aid of atmospheric-pressure plasma processes.
The basis of these coatings is aA microstructured surface which
has been provided with a hydrophobic top layer.
PHASE CHANGE MATERIALS
Phase change materials (PCM) take advantage of latent heat that
can be stored or released from a material over a narrow
temperature range. Working principle of PCM :
Figure . Change in phase change material with the
change in temperature.
This interesting property of PCMs would be useful for making
protective textiles in all-season. fibre, fabric and foam with PCMs
could store the heat body creates then release it back to body, as it
Coating, lamination, finishing, melt spinning, bi-component
synthetic fibre extrusion, molding, foam techniques are some of
the convenient processes for PCMs’ incorporation into the textile
Ex .PCM , SMM
SMART TEXTILES: Conductive Coating
Polypropylene (PP) and viscose (VS) were modified by the insitu synthesis of a
conducting Polypyrrole (PPy) overlayer.
To improve adhesion of the conducting layer to the textile surface a Pyrrole-
functionalized silane (SP) was synthesized and bonded onto the surface before
To introduce hydroxyl groups into the surface PP was pretreated by grafting
vinyltrimethoxysilane by means of a radiofrequency plasma discharge.
In the case of Polypropylene the effect of pretreatment with SP is much better than for
Higher concentration of SP leads to improved fastness of the conductive layer which
indicates that the coating promoted by means of SP is more favoured than for viscose.
• Two types of Di-ammonium hydrogen phosphate (DAHP)
microcapsules based flame retardent with respectively:
1. Polyether- polyurethane shell, and
2. Polyester-polyurethane shell, were evaluated as
intumescent flame retardant (FR) in a commercial poly-urea
coating for textiles
The advantages of this new concept of encapsulated FR agent
are to be compatible with a polymeric matrix in order to give a
permanent FR effect and to be itself an efficient FR
intumescent formulation for many materials.
• A novel antibacterial coating for cotton fabrics has been developed
using core-shell particles that consist of poly (n-butyl acrylate)
(PBA) cores and chitosan shells.
Spherical particles are prepared via a surfactant-free emulsion
The PBA-chitosan core-shell particles have a narrow particle size
distribution with average particle diameter of approximately 300 nm,
and display highly positive surface charges.
The cotton fabric is coated with PBA-chitosan particles by using a
conventional pad-dry-cure method.
PBA-chitosan particles demonstrates an excellent antibacterial activity
with bacterial reductions more than 99%.
ULTRA-EVER DRY COATING
• Ultra-Ever Dry is a superhydrophobic (water) and
oleophobic (hydrocarbons) coating that will repel most
water-based and some oil-based liquids.
• Ultra-Ever Dry uses proprietary omniphobic technology
to coat an object and create a surface chemistry and
texture with patterns of geometric shapes that have
“peaks” or “high points”. These high points repel water,
some oils, wet concrete, and other liquids unlike
any other coating.
• High adhesion and abrasion resistance.
• Translucent White colour coating by xylene(top)and
acetone(bottom) or nano composite polystyrene, Zinc
oxide polystyrene (ZnO/PS) nano-composite.
Ultra-Ever Dry Features
– The superhydrophobic coating keeps objects dry. Water
and many other liquids are easily repelled.
• Self-Cleaning -
– Repels dirty water and some oils, and remains clean and
– Dust, dirt or other molecules accumulate on
superhydrophobic coated surface, a light spray of water or
a blast of air grabs the dust and removes it.
• Ultra-Ever Dry can be used : Fabric Protect from acids/bases,
Fabrics used in Boats & marinas, Water /oil proofing fabrics
APPLICATIONS OF ADVANCE COATED TEXTILES
The coating and lamination gives a powerful tool for the
advancement of textile technology.
It provides the opportunities to produce the special fabrics like
water-proof resistant tarpaulins, coverings, large tents and
architectural uses, backcoating for upholstery including autoseats,
Food packaging, Medical applications, parachutes, Woven curtains
for heat- sensitive fabrics, automotive fabrics, disposable hospital
The recent developments also enhanced the lamination and coating
technique into state-of-art process of the future in textile field.