2. Introduction
PSA Tapes were first introduced about 150 years ago.
Initially medical tape
and dressing was developed and a U.S. Patent was
issued in 1846.
PSA’s are widely used since the 19 th century.
Industrial Tapes were introduced between the 1920 ,s
and 1930,s .
Hot Melt adhesives were introduced in the 1940,s .
PSA Tapes are used for many different Applications.
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3. What is pressure sensitive
adhesive ?
Pressure sensitive adhesive, is adhesive which forms a bond
when pressure is applied to bond it with the adherent. This is a
material that holds two surfaces together solely by surface contact,
which is achieved by slight initial external pressure. These
adhesives require no activation with water, solvent or heat, and
firmly adhere to many dissimilar surfaces with minimal pressure.
Aggressive and permanently tacky at room temperature, PSAs can
be used for bonding materials such as plastic, paper, metal, glass,
and wood.
As the name "pressure sensitive" suggests, the bond is influenced
by the amount of pressure that is applied on the adhesive to the
surface.
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4. Pressure sensitive adhesives are designed with a balance between
flow and
resistance to flow.
The bond forms because the adhesive is soft enough to flow,
or wet, the adherent.
The bond has strength because the adhesive is hard enough to
resist flow when stress is applied to the bond.
PSAs exhibit viscoelastic (viscous and elastic) properties, both of
which are used for proper bonding.
Pressure sensitive adhesives are characterized by their shear
holding. The ability to hold in a shear mode is related to the
formulation, coating thickness, rub-down, temperature, etc.
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5. Factors affecting ?
Surface factors , such as smoothness, surface energy, removal of
contaminants, etc. also , play important role in proper bonding.
PSAs are usually designed to form a bond and hold properly at
room temperatures. PSAs typically reduce or lose their tack at low
temperatures and reduce their shear holding ability at high
temperatures; special adhesives are made to function at high or low
temperatures. It is important to choose an adhesive formulation
which is designed for its intended use conditions.
Once the adhesive and the adherent are in contact, there are
molecular interactions such as , van der Walls forces , involved in
the bond, which contribute significantly to the ultimate bond
strength.
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7. Convenient & fast means of application.
Ease of removability without damage
of the substrate.
Wide choice.
Suitable for a number of applications.
Easy printability.
Easy laminate / bond ability
Easy cut ability , die- cut ability.
Structural integrity.
Dimensional stability.
Shape retention.
PSA Tapes
Key features
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8. Unique
Characteristics
Provide temporary and permanent holding
application.
Provide insulation , thermal as well as electrical.
Provide sound and vibration proofing.
Cheaper packaging solution.
Mounting.
Assembling.
Sealing
Splicing.
Medical / surgical mounting.
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9. For many years, rubber/resin formulations have been available that combine
natural or synthetic rubber with tackifying resins, oils, antioxidants, or other
ingredients as needed. They are typically either solvent-based or used in hot
melts, and the aggressive nature of rubber adhesives makes excellent
bonding easy to achieve.
These adhesives are known for their high level of adhesion to a variety of
substrates and facestocks, as well as their high coatability. Rubber-based
adhesives provide high tack and peel, and make excellent general-purpose
adhesives, because of their ability to adhere well to several non-polar, low-
energy surfaces, including polyethylene and polypropylene. In general, rubber-
based adhesives are often a more economical choice compared to most
acrylics.
Disadvantages of rubber-based adhesives include limited effectiveness when
exposed to certain chemicals, UV rays, or high temperatures (over
150°F/66°C). In addition, they are more susceptible to oxidation and may
darken, lose their tack, and become brittle if overexposed. Also, rubber/resin
adhesives may turn soft and gummy if plasticizers, used in most polyvinyl
chloride films (PVC), migrate into the adhesive.
Rubber Base
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10. The other type of adhesive chemistry commonly used in PSAs is acrylic.
Acrylic adhesives can either be solvent- or water-based, and are formulated by
reacting monomers with the desired properties, which are then typically
crosslinked to form the type of polymer needed. Monomers are the building
blocks of polymers and are considered to be either “soft” or “hard.” The
combination of hard and soft monomers can be adjusted based on the level of
adhesive (polymer) performance needed.
Crosslinking polymers improves the cohesive strength (internal strength of the
adhesive, or the ability to stick to itself) of the acrylic formulation and can be
accomplished in one of three ways: the use of thermal heat energy; by self-
curing when a solvent is removed during the drying process; or through UV or
EB non-thermal radiation.
In general, acrylics are relatively firm and durable, but are not as aggressive
as rubber-based adhesives. An acrylic adhesive can be modified to alter its
adhesion properties based on the selection of monomers used, the level of
polymerization created, or by adding tackifying resins or other chemicals.
Acrylic base
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11. The advantages of acrylic adhesives are typically the opposite of rubber
adhesives. Acrylics provide excellent temperature, UV and oxidation
resistance; therefore, they are often the preferred choice for outdoor
applications. They resist the negative plasticizing action that can occur with
rubber and hold up well to chemical exposure. Acrylic-based adhesives are
very durable and have clarity and color stability. Acrylics bond well to polar
surfaces like metal, glass, polyesters and polycarbonates, and have high peel,
tack, and shear.
Disadvantages of acrylics usually include poor adhesion to low-energy
surfaces, such as polyethylene and polypropylene, as well as lower overall
adhesion compared to rubber unless the adhesive is highly engineered. In
general, acrylics are often more expensive than rubber-based adhesives.
Acrylic base
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12. Silicone adhesives are another chemical option for PSAs but are less common
than rubber or acrylic. These specialized adhesives consist of silicone
polymers that provide adhesion to silicon and other hard-to-adhere-to
materials. Silicone-based adhesives can maintain adhesion over a range of
temperatures; however, beyond their ability to adhere to difficult surfaces, their
overall adhesive strength is low. Silicone adhesives are also more expensive.
Silicone base
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13. Characteristics of pressure
sensitive adhesive ?
Adhesion : Tack, Peel Resistance, Cohesive strength /
or Shear resistance.
Converting Properties : Printability, ability to
Laminate, Cut ability, Die-cut ability.
End Use Application : Ageing Resistance, Chemical
and water resistance, bonding and de bonding properties,
Process ability.
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14. Adhesion :
Tack, is the Wet ability of adhesive
is nothing but to form a bond in a short time , with little pressure . hence the
adhesive needs to have good flow.
Tack depends upon
1. Viscosity
The ability of the adhesive to flow and cover the applied surface to form a bond.
2. Modulus of elasticity
The modulus decided the de-bond ability of the adhesive without any kind of
adhesive failure , like leaving residue on the applied surface.
3. Time , temperature and external strain.
3.(a).Time and Temperature
Has direct effect on the performance of the PSA. Time and Temperature influence
the flow characteristics of the PSA
3.(b).External strain.
Tack depends on the peel off force and the speed of peel off. As the speed increases
the tack value tends to increase.
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15. Adhesion :
Tack,
Tack is the initial attraction of an adhesive to a
substrate—the instant grab of the adhesive, with no
external pressure applied.
Sometimes tack is referred to as "quick stick" or "thumb
appeal."
Tack properties are typically measured using the loop
tack test
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16. Adhesion :
Peel Resistance,
Peel is the force required to pull off the Adhesive from the applied surface
The peel strength depends upon ,
1.Viscosity
Viscosity has a direct effect on the peel strength. As the viscosity increases the peel
strength increases.
2.Modulus of elasticity
The modulus decided the de-bondability of the adhesive. Lower the modulus ,
easier is the removability of the product.
3.Time , temperature and external strain.
3.(a ).Time and Temperature
Has direct effect on the performance of the PSA. Time and Temperature influence
the peel str . of the PSA. More the dwell time more is the peel , but the peel
decreases as the temp increases.
3.(b).External strain.
Peel depends on the speed of peel off . As the speed increases the peel value
tends to increase.28-01-2013 16
17. Adhesion :
Peel Resistance,
The measure of bond strength between an adhesive
and a substrate is defined as adhesion.
It is important to note that this is the measure of bond
strength after pressure is applied to the adhesive,
allowing for wet-out onto the substrate.
Adhesion properties are typically measured using the
180° or 90° peel adhesion test method
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18. Adhesion :
Cohesive strength or Shear resistance.
Shear/cohesive is the holding power of adhesive is nothing but the resistance
to shear stress.
The shear depends upon
1.Viscosity
Increase in Mol.wt of a polymer increases the viscosity .The increase in viscosity
increases the shear strength.
2.Modulus of elasticity
The modulus decided the de-bond ability of the adhesive without any kind of
adhesive failure , like leaving residue on the applied surface. masticated rubber
posses a lower elastic modulus as compared to raw rubber obtained from
coagulated latex. The mastication processes reduces the modulus of the polymer but
does not alter the Glass Transition Temp. the reduction is modulus , results in
lowering the shear str.
3.Time , temperature and external strain.
Shear resistance of an adhesive depends on it’s internal cohesion , which is a
function of the inherent viscosity or modulus. Shear resistance is thus dependent on
the factors affecting the viscosity and modulus.28-01-2013 18
19. Adhesion :
Cohesive strength or
Shear resistance.
The internal or cohesive strength of an adhesive film is
known as shear. This is not a measure of the bond
between the adhesive and a substrate, but rather a
measure of the internal strength of the adhesive itself.
Shear properties are typically quantified using the static
shear test method
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20. The adhesive plays a very crucial role
in terms of performance of the
product. The real technology lies in
striking a balance of the three main
properties of adhesive , like the Peel
strength , the tack and the shear
strength.
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21. Co-related to
Adhesives , like
WB Acrylic / GP
HMPSA
For application , such
as
Packaging Tapes
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22. Co-related to
Adhesives , like
SB Acrylic
For application , such
as
Application Tapes,
holding Tapes,
Foam Tapes
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26. Further classification of pressure
sensitive adhesive ?
Water-based PSA (WB PSA) – a PSA applied in aqueous
emulsion form and dried to form the adhesive film
Solvent-based PSA (SB PSA) – a PSA applied in solvent
solution form and dried to form the adhesive film
Hot-melt PSA (HM PSA) – a PSA applied as a 100% solids,
thermoplastic composition in the molten state
Calendered PSA – a PSA applied as a 100% solids
composition in a calendering operation
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35. Suitable Solvents
Solvent Chemical formula Boiling point
Dielectric
constant
Density
Dipole
moment
Non-polar solvents
Hexane
CH3-CH2-CH2-
CH2-CH2-CH3
69 °C 1.88 0.655 g/ml 0.00 D
Benzene C6H6 80 °C 2.3 0.879 g/ml 0.00 D
Toluene C6H5-CH3 111 °C 2.38 0.867 g/ml 0.36 D
Polar aprotic solvents
Ethyl
acetate
CH3-C(=O)-O-
CH2-CH3
77 °C 6.02 0.894 g/ml 1.78 D
Acetone CH3-C(=O)-CH3 56 °C 21 0.786 g/ml 2.88 D
Polar protic solvents
Ethanol CH3-CH2-OH 79 °C 24.55 0.789 g/ml 1.69 D
Water H-O-H 100 °C 80 1.000 g/ml 1.85 D
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36. Hot-melt PSA (HM PSA)
SIS ready to use
EVA ready to use
SBS ready to use
SIBS ready to use
PU ready to use
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40. Types of PSA’ Tapes
We are going to talk more about Tapes in
this presentation
Single Side
Double Side
Reinforced
Unsupported
With liner
Without
liner
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47. variety of PSA’ Tapes
Fabrics based
Foam based
Non woven based
Metal foil based
Film Based
BOPP
PVC
Poly Ester
Poly Ethylene
Poly Amide
Cotton
Nylon
Rayon
Fiber Glass
Aluminum
Copper
Paper based
Kraft
Crepe
Poly Ester
PP
PU
EVA
Nitrile
EPDM
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49. Pressure sensitive adhesive tape
manufacturing process ?
Prior to the tape manufacturing process ,it is necessary
to understand the characteristics of the PSAs , and the
backing material / face stock / substrate and the
conditions under which they will be used
to satisfy end-use requirements without causing
process ability concerns ,
And this will lead to a successful product.
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50. Surface Contour. The contour of the substrate will influence product
selection (see Figure 3). For uses requiring conformability around irregular
angles, more flexible materials should be employed. Regardless of the
strength of the formulation, it is virtually impossible for an adhesive to
overcome a continuous stress placed on
it by a rigid material trying to return to its original form (memory). For such
applications, one should choose a conformable product with a tissue or
nonwoven carrier facestock or consider adding stress relief to the converted
part via scoring or perforation.
critical Issues are
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51. Surface Energy. The ability of an adhesive to wet out over the surface of a
material is related to its surface energy. Low-surface-energy (LSE) materials
do not allow the adhesive to wet out, whereas high-surface-energy materials
allow excellent wet-out and provide the best adhesion. Rubber-based
adhesives generally offer better adhesion to LSE substrates—a softer, better
flow. Some materials require special treatment—corona treatment, primers,
topcoats—to promote better adhesion. On some LSE materials, adhesion
levels will improve with longer adhesive dwell times.
critical Issues are
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52. PSA Tapes mainly consist of two main components , the carrier /
backing material and the Adhesive.
Generally Tapes are produced by coating a carrier ( or backing
material ) , such as plastic films , fabrics, paper or foil with a adhesive ,
which is normally in liquid form. These adhesives contain solvents ,
such as water, or organic chemicals such as toluene, ethyl acetate etc,
as carriers.
The solvent is evaporated with help of hot air impregnation , so that a
dry adhesive film is formed , above the backing material with a firm
bond .
In some cases the back-side of the tape is coated for non adhesive or
release properties, which helps to have easy unwind property , with no
adhesive transfer.
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53. The Backing material
The backing material is the most important component of PSA Tapes . The
backing or carrier provided the necessary strength and body to tape product.
The backing has to be sufficiently strong . the backing needs to have
reasonably good tensile strength , elongation , conformability, moderate heat
resistance , chemical resistance, abrasion resistance etc.
The various backing materials that are common in use are shown above.
The backing materials need a primer coat or chemical or physical , surface
preparation / treatment before adhesive coating.
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54. Surface Treatment
Plastics Films are widely used in Packaging applications such as Self Adhesive
Tapes, Laminates, Printing etc.
As we know all these films are chemically inert and have very low surface
energy. The below mentioned table gives an idea about the surface tension of
various polymers.
Sr.No. Polymer Surface Tension of
Homo polymer in
Dynes/Cm2
1 Poly Ethylene PE 31
2 Poly Propylene PP 32
3 Poly iso butylene PIB 27
4 Polystyrene PS 33
5 Poly Tetra Fluro Ethylene PTFE 19
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55. Surface Treatment
From the above tables it is very clear that the polymer surfaces need treatment
to enhance the wettability , printability , and adhesion properties. Or in other
words the surface tension has to match that of the coating materials.
The common methods of surface treatment for films are
chemical etching
flame treatment
carona treatment
plasma treatment
however chemical etching method is outdated.
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56. Surface Treatment
Flame treatment
In this process propane or butane flame is used to treat the polymer surface.
Here the electron density is lower and therefore the ionization rate .
The higher temp in the flame poses a problem for most polymer surfaces.
Carona treatment
Here the atmospheric air is ionized by help of high voltage transformer.
The mechanism is like this. Two idler rollers form the two electrodes. High
voltage of high frequency is produced with the help of a transformer. The high
voltage applied to the two electrodes . one electrode ( Idler is insulated with
silicone rubber coating , which is a perfect di electric.
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57. Surface Treatment
Plasma Treatment
Radio frequency ( rf) glow discharge ( Cold gas plasma) of hydrogen in
combination with vapourised liquid provides unique sueface modification.
In this method gas molecules are excited by subjecting to an electric field ,
typically radio frequency energy.
The radio frequency creates free electrons . these electrons gain energy from
imposed field and collide with Nat gas molecules. The collision and transfer of
energy form no of reactive species.
These particles interact with solid surfaces placed in the plasma.
This leads to dramatic modification of the molecular structure.
Hydrogen in composition with liquid oxygen contributing co-reactant is used as
the plasma. This creates stable oxygen moieties which is chemically reactive.
This reactivity is ideal for forming tenacious bonds with selected adhesives.
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58. Advantages of plasma.
get higher treatment levels , upto 60 dynes/ cm2.
no surface degradation
low temp process
the surface treatment has a long life
back side treatment is eliminated
treatment is permanent
viable alternative for carona treatment is ineffective especially on PTFE
electronic bombardment is 100% greater than carona.
treatment is uniform through out the surface
treatment on higher thickness , thicker than 0125 inch is possible.
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59. Surface Contamination. The presence of surface contamination such as
skin oils and bodily fluids can prevent contact of the adhesive with the
substrate. There are many different types of surface contamination, most of
which are not visible to the eye but can be identified analytically. It may not
be possible to obtain an acceptable bond without cleaning the surface (e.g.,
through washing or flame treating). Surface contamination may be present if
one can detect loose material on the surface of a substrate or the material
feels slippery, greasy, or slimy. Contamination may also be suspected if
testing indicates poor bond strength and the adhesive feels "dead" after
removal from the substrate.
critical Issues are
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60. Pressure sensitive adhesive tape
manufacturing process ?
Adhesive Coating
Rewinding and slitting or slicing
Testing
Packing
Drying
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73. Drying
Drying of coatings removes the inert inactive solvent used to
suspend , dissolve or disperse the active ingredients (
polymer , binder, pigments, slip agent, hardener , coating
aids etc. ) ,
so that only the desired coating remains on the desired
surface / substrate.
Solvents could be water , or active organic materials
Usually the drying process is a thermal one , in which heat
is supplied , to the coated fluid and the solvent in it is
vaporised.
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74. Drying
Coating - Drying Interactions
The purpose of drying process is to produce a uniform dry coating
from the applied wet coating , by evaporation of solvent .
If wet coating applied is uniform then the dryer must immobilize
it and maintain its uniformity throughout the drying process.
Drying and Coating processes are interdependent and interactive.
The requirements of coating process determine the drying
parameters.
The needs and limitations of dryer influence the coating process.
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75. Drying
A dryer designed to evaporate water differs significantly from one
intended for use with volatile organic solvent.
The bonder system influences the drying temp and air velocity.
A low viscosity formulation is far more susceptible to damage in the
dryer than a high viscosity one.
Lower air viscosity must be used in the drying process to avoid
moving the coating and damaging it.
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89. Please feel free to contact us
For more Information
Our website : www.psadhesive.com
Personal Email : psatechno@gmail.com
Cell : 00 91 9850242282
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