Chemical bonding involves applying a liquid binder to a nonwoven web to improve its characteristics such as strength and durability. Binders work by being applied to the web and then forming strong bonds between the binder and fibers as the moisture or solvent is removed. There are various types of binders classified based on their chemical structure and functionality, including acrylics, styrenated acrylics, and vinyl acetates. Common chemical bonding processes involve saturating, foaming, spraying, printing, or applying binder powders to nonwoven webs. The bonded webs find applications in products like wipes, medical fabrics, and apparel.

2. CHEMICAL BONDING
 Chemical bonding mainly refers to the application of a
liquid based bonding agent to the web.
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3. WHY NEED CHEMICAL BINDER?
 To improved characteristics such as strength, softness,
adhesion, firmness, durability, stiffness, fire retardence ,
hydrophilicity, hydrophobicity, anti-microbial properties,
organic compatibility, reduced surface tension, improved
dimensional stability and solvent, wash and acid
resistance.
 The required properties can be varied depending on the
end-uses.

4. PROPERTIES OF REQUIRED BINDER
Strength of nonwoven fabric related
to the strength of applied binder
Binder –to-fibers bond
When a soft hand nonwoven fabric
desired
Strength
Adhesion
to fibers
Flexibility/
handle

5. PROPERTIES OF REQUIRED BINDER
To avoid permanent deformation of fabric
Some need durability in cleaning process-
according to end uses
Binder should be stable and not degraded
in the fabric during storage and use
Elastic
recovery
Resistance
to washing
Resistance
to aging

6. PROPERTIES OF REQUIRED BINDER
Diverse ranges of colors are required, and the
colorfastness and yellowing problems should be
considered
Minimizing the cost is an ongoing requirement
Such as Flame resistance, resistance to
chemicals, air, oxygen, light, heat, etc.
Colour
retention
Economi-
cal
Special
require-
ment

7. HOW BINDERS WORK?
Binder
application to
nonwoven web
Removal
moisture or
solvent
Formation of
strong bond
(binder and
web)

8. Film Formation
Schematic of film formation
(source: http://www.engr.utk.edu/mse/pages/Textiles/Chemical%20Bonding.htm

9. CLASSIFICATIONS OF BINDERS
CHEMICAL
STRUCTURE
FUNCTIONALITY
CURING
REACTION
1 2
3

10. CLASSIFICATIONS OF BINDERS
 There are three main kinds of binders: butadiene
copolymers, acrylates, and vinyl copolymers.
 The chemical compositions influence Tg, hardness
and softness, hydrophobicity and hydrophilicity,
elasticity, aging, and dry tensile strength of
binders.
 The higher the Tg, the higher will be the dry tensile
strength of binders.
CHEMICAL
STRUCTURE
1

11. CLASSIFICATIONS OF BINDERS
 attached to polymer chains, which influences wet and
solvent properties.
 To modify binder properties, copolymerization with a
small amount of monomers with special functionality
is performed.
 The main functionalities in binders are carboxyl and
amide side chains.
FUNCTIONALITY
2

12. CLASSIFICATIONS OF BINDERS
FUNCTIONALITY
2
Carboxyl
• related to binders containing acrylic acid or methacrylic
acid by copolymerization.
• The binders are crosslinkable since the functional group,
carboxylic acid, provides sites for crosslinking reactions.
Amide
• is related to binders containing acrylamide by
copolymerization.
• The amide functionality provides crosslinking sites, and
even the binders are self-crosslinkable.

13. CLASSIFICATIONS OF BINDERS
CURING
REACTION
3
 refers to crosslinkability of binders, which is related to
reaction with curing resins, crosslinking agents.
 The most common curing resin is melamine
formaldehyde condensate resin involving reaction of
n-methylol groups.

14. TYPES OF BINDERS
• offer the greatest durability, color stability, and
dry/wet performance. Acrylic binders have the
widest range of fabric hand properties. They
can be formulated to vary from very soft (Tg = -
40°C) to extremely hard (Tg = 105°C).
ACRYLIC
• tough, hydrophobic binders. The resulting
textile hand ranges from soft-to-firm (Tg varies
from –20°C to +105°C ).These binders can be
used in applications where there is a need for
some wet strength without crosslinking.
STYRENATED
ACRYLICS

15. TYPES OF BINDERS
• The vinyl acetate binders are firm (Tg = +30°C to +40°C);
however, they are relatively low cost and find extensive use.
They offer good dry strength and toughness, but are
somewhat hydrophilic and have a tendency to yellow when
subjected to heat.
VINYL
ACETATE
(VAC)
• These binders are more hydrophobic than the straight VAC
binders. They provide excellent toughness, flexibility, and
better color stability. They are the compromise between VAC
and acrylic, and can compete on a cost/performance basis.
The hand range is limited to intermediate softness (Tg = -
10°C) to a firm hand (Tg = +30°C).
VINYL
ACRYLICS

16. TYPES OF BINDERS
• These latex binders have a (Tg range of –20°C to +115°C,
which is equivalent to soft ranging to an intermediate textile
hand. They exhibit high wet strength, coupled with excellent
absorbency. In general, they are less costly than acrylics.
They do have a tendency to have more of an odor compared
to other binders. They are used primarily in wipes, air-laid
pulp fabrics and similar applications.
ETHYLENE
VINYL
ACETATE
(EVA)
• These binders have an excellent combination of flexibility
and toughness. When cross-linked, this class of binder is
very hydrophobic and durable. They are affected somewhat
by heat and light because of their tendency to oxidize.
STYRENE-
BUTADIENE

17. TYPES OF BINDERS
• The homopolymer of polyvinyl chloride is a very hard,
rigid polymer (Tg = +80°C). This polymer must be
plasticized to provide flexibility and film-forming
properties. As it is a thermoplastic, it performs well in
heat and dielectric sealing applications.
POLYVINYL
CHLORIDE (PVC)
• have a slightly broader hand range (Tg = 0°C to +30°C).
• presence of the chlorine again conveys some flame
retardancy. These binders exhibit good acid resistance,
fair water resistance, and excellent adhesion to
synthetic fibers. There is some tendency to yellow upon
aging.
ETHYLENE/VINYL
CHLORIDE

18. FORMULATION
 Is an art since many ingredients are involved and many
different possibilities exist for different end-uses.
Surfactants
External
cross-linkers
Defoamers
Repellent
agents
Salts Thickeners Catalysts
Acids and
bases
Dyes and
pigments
Fillers
Optical
brighteners
Sewing aids

19. FORMULATION
 Surfactants : offer improvement in binder adhesion, stability,
and ability to be converted into a foam
 External cross-linkers: provide cross-links with binder polymer
to provide improved performance
 Defoamers: utilized to minimize foam in processing
 Repellent agents : convey water or oil repellency
 Salts: added to impart low flame response properties and to
convey antistatic properties
 Thickeners: added to control the rheology of the binder liquid
 Catalysts: added to facilitate curing and to promote cross-linking
 Acids and bases: added to control pH of the latex
 Dyes and pigments: provide color to the binder and fabric

20. ORDER OF FORMULATION
Most
ingredients
Latex
binder
Thickener
Catalyst
Some water,
dye etc

21. CHEMICAL BONDING PROCESS
Saturation Foam Spray
Print Powder

22. CHEMICAL BONDING
PROCESS
Saturation
Saturation chemical bonding involves complete
immersion of the nonwoven web in a bath containing
binder.
Excess binder is removed by vacuum or roll pressure.

23. CHEMICAL BONDING
PROCESS
Saturation
For fabric applications which require strength,
stiffness, and maximum fiber encapsulation, such as
carrier fabrics.
Three variations of saturation bonding exist: screen,
dip/squeeze, and size-press. Screen saturation is used
for medium-weight nonwovens, such as interlinings.
Dip/squeeze saturation is used for web structures
with strength sufficient to withstand immersion
without support, such as spunbonds. Size-press
saturation is used in high speed processes, such as
wet-laid nonwovens.

24. CHEMICAL BONDING
PROCESS
Saturation
The amount of binder taken up by the nonwoven
depends on the basis weight of the nonwoven, length
of time spent in the bath, wettability of the fibres and
nip pressure.
Drying and curing may be carried out on steam-
heated drying cans or in thru-air ovens or perforated-
drum dryers.

25. CHEMICAL BONDING
PROCESS
Foam
Foam bonding is a means to apply binder at low
water and high binder-solids concentration levels.
require less energy in drying, since less water is
used.

26. CHEMICAL BONDING
PROCESS
Foam

27. CHEMICAL BONDING
PROCESS
Spray
binders are sprayed onto moving webs.
used for fabric applications that which require the maintenance
of highloft or bulk, such as fiberfill and air-laid pulp wipes.

28. CHEMICAL BONDING
PROCESS
Print
applies binder only in predetermined areas.
It is used for fabric applications that require a part of
the area of the fabric to be binder-free, such as wipes and
coverstocks.

29. CHEMICAL BONDING
PROCESS
Powder
Adhesive powder of thermoplastic polymers is applied onto
webs by heat and pressure. Polyesters and polyolefins with
low Tg's and molecular weight can be used as powder binders.

30. METHODS OF DRYING

31. APPLICATIONS
 Wipes and towels
 Medical nonwovens
 Roofing products
 Apparel interlinings
 Filter media
 Coating substrates
 Automotive trim
 Carrier fabrics
•Bedding products
(high loft)
•Furniture
applications (high
loft)
•Apparel Pillows
(high loft)