There are three main types of adhesives used in footwear manufacturing: solvent-based adhesives, water-based adhesives, and hot melt adhesives. Solvent-based adhesives typically contain a resin dissolved in a solvent, while water-based adhesives suspend the resin in water. Hot melt adhesives are initially solid and become liquid when heated for application. Common adhesive types include neoprene, polyurethane, latex, and EVA. Proper surface preparation of materials like leather, rubber, and textiles is important for achieving a strong bond.

1. Adhesives

2. What is Adhesive?
A substance used to stick objects or materials together
is known as an Adhesive.

3. Type of Adhesives
There are a large number of adhesive types for various applications.
Adhesives can be classified in a number of ways.
Properties:-
• Thermoplastic Adhesive
• Elastomer Adhesive
• Thermoset Adhesive
Composition:-
• 1 Component Adhesives
• 2 Component Adhesives
Use:-
• Contact Adhesive
• Pressure Sensitive Adhesive
• Hot melt Adhesive
Curing Type:-
• Physical Curing Adhesive
• Chemical Curing Adhesive

4. Adhesives in Footwear
There are three main type of adhesives used in footwear.
• Solvent Based Adhesives
• Water Based Adhesives
• Hot melt Adhesives

5. Solvent Based Adhesives
Adhesive usually contain two components.
1. Resin
2. Carrier
In Solvent based adhesives, the base resin is dissolved in Solvent.
When applied to a surface, the solvent evaporates leaving the base
resin on the surface.

6. Solvent Based Adhesives
Solvent Based Adhesives for footwear usually are of two types.
1. Rubber Adhesive
2. Poly Urethane Adhesive

7. Rubber Adhesive
In Rubber Adhesive, a rubber resin is dissolved in solvent. The properties and use of
the adhesive depends upon the type of rubber resin.
• A rubber compound dissolved in solvent can be used to bond two rubber
components and is curable. This is a weak adhesive and needs curing.
• A Neoprene or Poly-Chloroprene Rubber dissolved in solvent is used for bonding
textiles, rubber layers, other components which are to be stitched. This is a weak
adhesive and can not be used where stress is applied. When temperature increases,
the bond starts to weaken. Examples are Samad Bond etc.

8. Rubber Adhesive
• Grafted Neoprene Adhesives are modified Neoprene Adhesives. These have
improved strength as compared to Neoprene and are less susceptible to
opening with increase in temperature. Examples are Diamond Bond.

9. Polyurethane Adhesive
Polyurethane adhesives are made by dissolving Thermoplastic Polyurethane (TPU) in a
solvent. PU Adhesives have far better strength than Rubber adhesives hence these can be
used in areas that come under stress such as Sole bonding. The downside of the PU
adhesives is that they do not have any tack so once dry these do not stick. Hence to get
bonding, the components need to be heated to make the top surface tacky. We call this Re-
activation. PU adhesive usually take up to 24 hours to complete its bonding. In order to
reduce this time, a Cross linker or Hardener is added to the PU adhesive which creates
additional crosslinks and improves the bonding efficiency. Usually 2.5 to 5% hardener is
added to the adhesive. Hardener also ensure proper bond even at higher temperature.

10. Polyurethane Adhesive
Examples of PU adhesives are Democol (Bayer), Pearlstick (Merquinsa)
and Keck Bond (Keck).
Example of Cross-linker or
hardener are Desmodur (Bayer) etc.

11. Water Based Adhesive
In Water based adhesives, the base resin is suspended in Water instead
of a solvent.
The water based adhesives work in similar way to the solvent based
adhesive. When applied to a surface, the water is evaporated leaving
the film of base resin on the surface.
Water based adhesives are also of two types.
• Rubber Adhesive
• Polyurethane Adhesive

12. Rubber Adhesive
Most widely used example of Water based Rubber adhesive is Latex.
In Latex, Natural Rubber particles are suspended in water.
Synthetic latexes made from Synthetic Rubbers are also used.
Also available are Water based Neoprene which is similar to its Solvent
based counterpart.

13. Polyurethane Adhesive
Similar to Solvent based PU adhesive, water based version is also
available. Its use and properties are similar to the solvent based PU.
The only drawback is that for solvents it is quite easy to dry even at
room temperature but in case of water the adhesive has to be heated
at least at 70° C to force the water out. Also in humid conditions, it is a
must to use higher dose of hardener to safeguard against moisture
failure.

14. Hot Melt Adhesive
Hot Melt Adhesives are those adhesives which need to be heated for
application. These are initially in solid form and upon heating become liquid
and thus applicable. In footwear these kind of adhesives are normally used in
Lasting, Toe imprinting, Last tacking etc.
There are many types of Hot Melt adhesives in use in footwear.
1. Polyester – White – Lasting (Fore part)
2. Polyamide – Yellow – Lasting (Sides)
3. EVA – Last tacking, shank fixing
4. PS/EVA – Counter stiffener

16. Pros and Cons
Type Use Advantage Dis-Advantage
Solvent Based Neoprene Lamination, Joining Tack, quick drying Solvent, heat tacking
Water Based Neoprene Lamination, Joining Tack, No solvent Drying, heat tacking
Solvent Based PU Sole Bonding Strength, moisture
resistance
Solvent
Water Based PU Sole Bonding No solvent, less quantity
used
Drying, susceptible to
moisture
Hot melt Lasting, Tacking, Stiffener Easy to use Smell, very small
application window

17. Grain Leather (resin finished,
aniline, nubuck etc
Rough or scour to remove
any finish and grain layer
Polychloroprene or PU (PU
adhesives better on greasier
leathers).
Priming is recommended
before cementing
Suede Lightly rough or scour fibres
flattened by lasting absorbent
leather
Finished splits Rough or scour to remove
finish and tease up leather
fibres.
PU Patent Rough or scour to remove PU
film (and leather grain if
present), to within 3mm of
edge of sole
PU + 2.5% isocyanate
PU coated (e.g. scuff
resistant)
Rough or scour to remove PU
coating or MEK solvent wipe
to clean surface
PU + 2.5% isocyanate
PVC coated Rough or scour to roughen
PVC film but not remove it or
MEK solvent wipe to clean
surface
PU + 2.5% isocyanate
Recommended Bonding systems for
shoe Materials
UPPER MATERIALS
Upper material Preparation Adhesive
Leather

18. Upper material Preparation Adhesive
PVC coated fabrics
All types Either: Rough or scour just to
remove finish layer but not remove
coating, or solvent wipe (MEK) or
EA to remove finish
PU + 2.5% isocyanate
Synthetic suedes
PU or PVC MEK or EA solvent wipe (rough to
disturb the surface layer)
PU + 2.5% isocyanate
PU Coated Fabrics
All types Rough or scour to remove PU
coating completely, except for
3mm band around feather.
PU + 2.5% isocyanate. Two coats
usually necessary to avoid
starvation if the textile base is
exposed.
Poromerics
All types Rough or scour into surface micro
porous layer
PU + 2.5% isocyanate.
Most natural and certain synthetic
fibred materials
None usually necessary PU or polychloroprene. Two coats
usually beneficial (two
component)
Textiles
Difficult materials including nylon Lightly rough or scour if
practicable. Prime with isocyanate
or special SATRA primer.
Two component adhesives are
often needed.

19. Sole material Preparation Adhesive
SOLE MATERIALS
Leather
Rough. Loose flesh fibres
should not be present
Polychloroprene or PU (two
coats) adhesives.
Vulcanized Rubbers
Special polychloroprene or
PU.( two component
adhesive)
Halogenate (e.g. Satreat or
Super Satreat) by soft brush
or spray.
Solvent wipe (petroleum
spirit
Thermoplastic rubber (TR)
PU + 2.5% isocyanate
Special crepe primer or
halogenate (e.g. Satreat or
Super Satreat
Natural crepe rubber
PU + 2.5% isocyanate
Scour or rough
Halogenate (e.g. Satreat). A
pre-rough or lacsol prime is
often beneficial
Moulded units and sheet
material including vulcanized
and gristle rubbers
Polychloroprene + 5.0%
isocyanate
Scour, rough or lacsol prime
Halogenate (e.g. Satreat) or
special rubber primer.
Resin or micro rubber
Adhesive
Preparation
Sole material
pu + 2.5% isocyanate

20. Sole material Preparation Adhesive
PVC
Solid including blends Citrus cleaners (textured
wipes) or MEK wipe
PU+ 2.5% isocyanate
Cellular Light rough and MEK wipe
Microcellular EVA
Scour or MEK solvent wipe Polychloroprene + 5.0%
isocyanate
Special EVA primer or
isocyanate primer
PU + 2.5% isocyanate
Cellular Rough or clean well with
Citrus cleaners (textured
wipes) or solvent wipe
PU + 2.5% isocyanate
Solid ROUGH OR Citrus cleaners
(textured wipes) or solvent
wipe
PU + 2.5% isocyanate
Polyurethane
NYLON Rough plus isocyanate
prime or special prime
Polychloroprene or two-
part PU

21. Thank You