Solvent-Free Polyurethane based Pressure Sensitive
Adhesive for Transdermal Drug Delivery Patch System
Norazwani Muhammad Zain1, Farizah Adliza Ghazali2 and Sahrim Ahmad3
1Mechanical & Fabrication Section, Universiti Kuala Lumpur Malaysia France Institute, Section 14 Jalan Teras

Jernang, 43650 Bandar Baru Bangi, Selangor, Malaysia.
E-mail: norazwani@unikl.edu.my
2Mechanical & Fabrication Section, Universiti Kuala Lumpur Malaysia France Institute, Section 14 Jalan Teras
Jernang, 43650 Bandar Baru Bangi, Selangor, Malaysia.
E-mail:farizahadliza@unikl.edu.my
3Faculty Science & Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia.
E-mail:sahrim@ukm.my

This research is carried out to focus on the development of solvent free polyurethane based pressure sensitive adhesive for medical patch products by using simulation methods. It presents an interesting class of
product that offers great potential to produce a new generation of palm oil bio-based pressure sensitiveadhesive with excellent properties that follow medical requirements. The objective of this study is to optimize the formulation of palm oil-based solvent free polyurethane pressure sensitive adhesive. It focuseson making a highly tolerable, comfortable product, characterized for good skin, and optimal release. This
study also focuses on the effect of different percentages and types of anti-flaming agent and various typesof tackifiers on fire resistance and mechanical properties of polyurethane based pressure sensitive adhesive.
Development in solvent-free polyurethane based pressure sensitive adhesive describe the variety of solvent
free polyurethane composition, residue monomers content, quality of tack, peel adhesion level repeating
during time, biocompatibility of solvent free polyurethane adhesive layers, permeability to air, water vapor,and their practical for medical application. The flammability resistance of pressure sensitive adhesive,
flammability test being was simulated and anlalysed according to the ASTM D 635 standard test method
for rate and / or extent and time of burning of plastics in a horizontal position. For mechanical properties,
the simulation of testing was performed according to ASTM D 3330 method b for 180 degree peel adhesion
to the backing of single coated tapes of pressure sensitive tape, and ASTM D 2979–95 for pressure sensitive adhesive tack test. This research was performed using Comsol Multiphysics software simulation. This
research is very important, and the testing method used in this research may enhance the strength andtoughness of pressure sensitive adhesive. It may be useful to engineers in the medical industry to increase
the strength of the pressure sensitive adhesive in the critical area of joining.
Key Words : Pressure Sensitive Adhesive, Polyurethane based adhesive, simulation study

Polyurethane adhesive contains carbamate groups-NHCOO- or isocyanate groups in strand adhesive of-NCO. Polyurethane adhesive has some characteristics which is higher reactivity, to containing activehydrogen or substrate adhesive strength with higherof water imbibition, can be used in room temperature
curing, can also be heating and curing, structure ofcrosslinking easy to form, high glue-line hardness,convenience easy to operate, low temperature resistant, excellent performance, good flexibility, fatigue performance is good, vibration, and impact
resistance. Incorvia. (2015).
In comparison to other groups of petroleum-based
polyurethane, pressure sensitive adhesives based on
certain types of palm oil-based solvent-free polyurethane provide intriguing advantages. As a sol-

1. INTRODUCTION
Pressure sensitive adhesive (PSA) is typically used
for a variety of self-adhesive materials such as adhesive one-sided, double-sided, adhesive labels, andprotective foils such as medical pads.
According to Singh et al., (2011), adhesive meant
for attaching two surfaces together mainly for ensuring surfaces remain attached with each other. For
this, adhesives are applied on the surfaces to be attached with each other. An adhesive is a liquid orsemi-liquid mixture that adheres or bonds two or
more objects together. Adhesives can be natural orsynthetic, and the sorts of materials that can bebonded are numerous, but they are particularly usefulfor bonding thin materials.
1vent-free system, a solvent-free polyurethane pressure-sensitive adhesive can be used. Excellent ageing
properties, resilience to high temperatures and plasticizers, remarkable optical clarity due to polyester
compatibility, and non-yellowing are just a few of thebenefits. It possesses the best adhesion, cohesiveness,
and water resistanceThe capability of medical solvent-free polyurethane based on pressure sensitive adhesive to adhere
well to varying skin types, both dry and moist, is oneof the most demanding performance requirements. It
should not irritate the skin and can be removed
without leaving adhesive residue or causing skinharm. Medical pressure sensitive adhesive adheres
strongly to the skin but can be easily removed withlittle or no stress to the skin due to adhesion capabilities and without adhesive due to cohesion properties. Pressure sensitive adhesive adhere too aggressively might cause skin irritation and pain. Low
tack or peel adhesion strength values render a patch
aesthetically undesirable when applied on the skinfor a long time, as adhesive oozes leave adhesive
residue on the outside edge of the backing layer.
Patches might leave noticeable remains when they
are removed. Tack and peel adhesion strength arehence extremely important pressure sensitive adhesive characteristics.
Basic trending criteria in the development ofpressure sensitive products are the type of raw materials, accessible technologies, and application. The
use of highly tolerant compounds with low allergenic
potential is the most important aspect when it comesto raw materials, and the options are further limited
by other factors. Pressure sensitive adhesive forpatches must be biologically inert, non-irritating, andnon-sensitizing at the skin's surface, and it must
provide good adhesive properties to the end product.
Singh et al., (2011).

systems in industries are also flammable and cancause health problems.
Solvent systems are also flammable that can contribute to fires and explosions. It is important to know
the flashpoint to describe when enough points aredischarged, a spark of flame can ignite. Flammability
may be identified when flammable solvents have a
flash point temperature of less than 100° F, while
combustible solvents have a higher flash point temperature. By the way, the solvent system is also
flammable in a structural material or part of the
product being made and used either for resource orexternal adhesive loads being applied.
Secondly, solvents can harm health and have twodifferent effects on skin. First, certain solvents can beabsorbed via the skin, where they might damageorgans or other systems. Solvents can bring harmful
compounds with them in some cases. The second
way is to irritate the skin, resulting in dermatitis.
Many solvents attack the natural oil that protects theskin, causing it to dry out or break out. Solvents canalso aggravate or cause skin allergies, causing painful
irritation. As the skin is exposed to more solvent, it
becomes more sensitive, which worsens the irritation.
Therefore, this research will focus on formulating
the invention of solvent-free polyurethane based onpressure sensitive adhesive using bio-based oil likepalm based oil that we believe to overcome theproblem.
(2) Objective••(1) Problem Statement
Solvent-free polyurethane-based pressure sensitive adhesive is now widely utilized in a variety ofindustries due to its excellent drying and adhesive
qualities, particularly endurance. However, solvent
polyurethane based pressure sensitive adhesive canbe unexpectedly tricky particularly for the research.
When solvent polyurethane based pressure sensitive adhesive is performed improperly, this can resultin a few different defects because it uses petroleum-based derived components which are polyether
polyol or polyester. Because of this situation, the newresearch of solvent-free polyurethane based pressure
sensitive adhesive using bio-based oil should be
looked out for. We already know that existing solvent•

To optimize the formulation of palm oil based
solvent free polyurethane pressure sensitiveadhesive by using Taguchi method.
To study the effect of different percentages andtypes of anti-flaming agent on fire resistanceproperties of polyurethane based pressure sensitive adhesive by simulation using Comsol
Multiphysics.
To assess the effect of various types of tackifier
on mechanical properties of polyurethane basedpressure sensitive adhesive by simulation using
Comsol Multiphysics.

(3) Significant of Project
The significance of this study is, it gives back thebenefits to the society and industries considering thata new biodegradable solvent free polyurethane basedpressure sensitive adhesive for medical patch products is an important role in manufacturing newtechnologies of pressure sensitive adhesive.
Pressure sensitive adhesive is unique in that it does2

not solidify into a solid material and instead remains
viscous. As a result, it is always tacky and can wet
surfaces when it comes into contact with it. According to Ebnesajjad, S. (2011)., By putting theadhesive sheet into contact with the substrate andexerting pressure, bonds are formed. It works well for
temporary adhesion.
The viscoelastic nature of pressure sensitive adhesive response to mechanical and climatic stress interms of durability is different from most structural
adhesives. There are many sectors that use the pressure sensitive adhesive such as packaging, automotive, building, medical and health, etc. Bahadori, A.
(2015).

blies to heat and flame in controlled settings, but itlacks the information needed to assess fire hazards orrisk in materials, products, or assemblies under actual
fire circumstances. Load, U. F., & Meth, V. F. T.
(2003).
Factors including density, pigments, any anisotropy in the material, and the thickness of the specimen affect the rate of burning and other burning
events. Whether comparing the same or different
materials, test data should only be compared forspecimens of identical thickness. With increasing
thickness, the rate of burning and other burning
phenomena will change. Load, U. F., & Meth, V. F.
T. (2003).
Tack test

2. METHODOLOGY

According to ASTM D 2979-95, pressure sensitive
tack of adhesives using an inverted probe machine,
the probe tack test is designed to be used with adhesives on flexible or stiff backings. The tests are used
for quality assurance and research. Polyken Tack
Tester was used to create the standard procedure. A
variety of probes can be used. The standard probe is astainless steel probe with a radius of 5 mm. This
results in a contact area of about 20 mm2. To reducethe chance of air trapping between the probe and theadhesive, the probe can be somewhat domed. Contactpressure (100 g cm-2), dwell time (1 s), and test
speed are the normal test settings (1 cm s-1). ASTM,(2001).

(1) Stages of research
To fulfil the objectives and goals of the research,
three steps of scientific research must be completed
in order to assure the systematic collection of data as
well as intelligence and to improve the precision of
the findings. This research began with the design ofan experiment utilizing the Taguchi method to determine the best formulation, followed by a simulation study on adhesive bonding preparation andcharacterization, and ultimately the validation process.
(2) Characterization of solvent free polyurethane
adhesive bonding

Peel test
According to ASTM D 3330 method b – 180 degreepeel test adhesion to backing of single-coated tapes isquite similar to method a, which measures the adherence of two layers of single coated tapes to eachother, but method b measures the adherence of twolayers of single coated tapes to each other. For information, application of method a is usually used formeasuring the adhesion of fastening tapes while
method b is usually used for measuring the adhesionof masking and packaging tapes. The result of thistest is used to determine the adhesion uniformity of apressure sensitive adhesive tape. A strip of tape is put
to a stiff substrate in this test, and then another strip isapplied to the backing of the first strip. After that, it isput to the test for peel adhesion. ASTM, (2003).

This simulation scenario is focusing on different
percentages and types of anti-flaming agent, and also
to assess the effect of various types of tackifiers onmechanical properties of polyurethane based pressure sensitive adhesive.
The simulation mimicking real life experiment andthere are three important testing model that need to beconstructed which is:
Flammability test
According to ASTM D 635: Standard test method for
rate of burning and / or extent and time of burning ofplastics in a horizontal position, this fire test response
test technique describes a small-scale laboratory
screening approach for comparing the relative linear
rate of burning, or extent, and time of burning, orboth, of plastics in the form of bars, molded, or cut
from sheets, plates, or panels, and tested horizontally.
This standard is used to measure and describe the response of materials, products, or assem-(3) Parameters
As we all know, parameters were the most important
thing in the process of making a new solvent freepolyurethane based pressure sensitive adhesive.
Three formulation parameters level rates have been3

selected based on the anti-flaming agent type, anti-flaming agent content, and type of tackifier. Usually, there are each certain function for each type of
the parameter. Table below show the specific parameter use in this research:
Table 1 Selected values of process parameter
Code

Factors

AFA

Anti flaming
agent types

AFC

Anti flaming
contents
Type oftackifiersT

Fig. 1 Flammability test simulation 1

Levels1

2

3

Phosphorous
flame
retardant
0.5%

Nitrogenflame
retardant

Halogenflame
retardant

1.0%

1.5%

Hydrocarbon
resinsRosin
resinsTerpeneresin

Fig.1 shows a plot of simulation models that havebeen carried out from the flammability testing. It isshown that the distribution of heat transfer of theburning range in the simulation model spreads theheat energy outward. This is because the surface ofthe model first contacts the heat source in the startarea. This first area of the model has high energy
particles that move aggressively then collide withother particles which are lower energy while
spreading the heat energy to the other particles.

Table 2 Orthogonal array design
Simulationno.

Control factors
AFA

AFC

T

1

1

1

1

2

1

2

2

3

1

3

3

4

2

1

2

5

2

2

3

6

2

3

1

7

3

1

3

8

3

2

1

9

3

3

2

Fig. 2 Flammability test simulation model 1
The stripe color was the red spot which had thehighest heat input, and the yellow spot at the end of
the simulation model with the lowest heat temperature. This proves that from the simulation of the
flammability test, the burning range of heat energy
has been transferred from high energy to lower energy in the end of the model area spread outward
from it based on the stripe color. The stripe color
shows the formation of heat transfer of the burning
range where the formation and the size of the flame
test start from red spot to yellow spot.

3. RESULTS AND DISCUSSION
The result from simulation studies consists of threedifferent testing which are flammability, peel, andprobe tack tests. The data will show in the stripes ofcolor from red which means highest to dark blue
which means the lowest. The result stripes also show
the maximum and minimum value area of testing andbeing discussed in the results data by simulation. The
simulation tests run smoothly without any problem.

(2) Probe tack test
Simulation of probe tack testing is conducted following ASTM D 2979-95 standard test method forpressure sensitive adhesive using an inverted probe
machine for tack test. The graph shows simulation
models that were conducted as a result of the probing
tack testing. According to the results, the greatest
recorded force necessary to detach the adhesive surface from the cylindrical probe represents the tack ofadhesion.

(1) Flammability test
Simulation of flammability testing is conducted following ASTM D 635 standard test method for rateand / or extent and time of burning plastics in a horizontal position.
4

Fig. 3 Probe tack test simulation 1

Fig. 5 Peel test simulation 1

This is due to the fact that the test examines the brieftime of adhesion with low pressure on a flat and cylindrical probe to the adhesive surface. The greatest
recorded force necessary to separate the adhesive
surface and the cylindrical probe represents the tackof adhesion and decohesion strength.

The graph shows graphs of simulation models thathave been carried out from the 180 degree peel testing. The result shows that the peel of maximum recorded force required to separate the adhesive surface
from the specified stainless steel plate surface represents adhesion. This is because the test measures
the adhesion peel strength of the adhesive's surface,which can be classified as low, medium, or high.
High or low peel force is not really a good
indicator of a pressure sensitive adhesive's effectiveness. Most stick-to-skin applications would not
require a particularly strong pressure sensitive adhesive, and a blood glucose meters display would not
require an easy peel pressure sensitive adhesive.

Fig. 4 Probe tack test simulation model 1
The pressure sensitive adhesive tape was simulated in
fixed condition, which eliminates tape backing effects. The speed with which the cylindrical probe
approaches the adhesive surface, which was controlled by the simulation force, and the speed withwhich the cylindrical probe is removed from theadhesive surface, which is controlled by the test,
measures the short time with low pressure of adhesion on a flat and the cylindrical probe to the adhesive surface. Red stripe color spot which has been
loaded with high impact pressure, and the blue spot at
the lower with lowest impact pressure. This has
proven that, from the simulation of the probe tack
test, the greatest recorded force necessary to separate
the adhesive surface and the cylindrical probe depending on the stripe color represents the tack ofadhesion strength. It should be noted that when different materials are utilized to simulate probe tacktests, the simulation results may different.

Fig. 6 Peel test simulation model 1
The pressure sensitive adhesive tape is simulated in
180 degrees peel angle condition. This test is tomeasure the release liner's adherence to the adhesive
and the pressure sensitive tape's adhesion uniformity.
The liner is pulled from the sticky surface and theadhesive tape is simulated with the linear side up.
The peel adhesion of pressure sensitive adhesive witha 180-degree peel is also measured in this test. The
stripe color is the red spot which has been loadedwith high force pressure, and the blue spot at thelowest force pressure. This proves that from thesimulation of the peel test, the adhesion strength of
maximum force necessary to separate the adhesive
release liner of pressure sensitive adhesive tape basedon the stripe color. From this peel simulation, it can
improve the comprehension of the element that influences the feel force, which has previously been
linked to skin trauma generated by peeling pressure
sensitive adhesive tape.

(3) Peel test
Simulation of peel testing was conducted following
ASTM D 3330 Method B for 180-degree peel adhesion to the backing of single coated tapes of pressure
sensitive tape.

5

Table 3 Orthogonal array design
Simulation

Control factors

Flammability rate (V)Peel strength (N)Tack strength (N)

1

1.85

2.39

2.2

2

2

1.88

2.25

2.05

1

3

3

1.96

2.45

2.15

4

2

1

2

1.81

2.45

1.7

5

2

2

3

1.91

2.05

1.93

6

2

3

1

1.86

2.4

1.7

7

3

1

3

2.0

2.05

2.09

8

3

2

1

1.66

2.18

1.68

9

3

3

2

2.08

2.3

1.95

no.

AFA

AFC

T

1

1

1

2

1

3

(4) Optimization by Taguchi and ANOVA

Response table for means

The Taguchi analysis has proven to be an effectivemeans of increasing productivity in research anddevelopment. As a result, higher-quality products canbe created rapidly and at a low cost. This techniquealso be used to limit the number of test subjects andarrange the study schedule.

Table 5 Means value

1-Taguchi analysis: Flammability rate (V), Peelstrength (N), Tack strength (N) versus Anti-flaming
agent types, Anti-flaming contents, Types of tackifiers.

Table 4 Signal to noise ratio
AFA

AFC

T

1

6.460

6.116

5.759

2

5.728

5.717

6.093

3

5.913

6.269

6.251

Delta

0.732

0.552

0.492

Rank

1

2

3

AFA

AFC

T

1

2.131

2.060

1.991

2

1.979

1.954

2.052

3

1.999

2.094

2.066

Delta

0.152

0.140

0.074

Rank

1

2

3

Table 5 shows the means that get from the Taguchi
method in Minitab 18. The rank is the influence forthe factor because the number 1 rank is most important because of anti-flaming agent types give a
specific level of ignition resistance followed by rank
number 2 which is anti-flaming agent contents thatprovide particular level of flame spread. For rank
number 3 which is type of tackifier, the best tackifiercompounds help balance pressure sensitive adhesive
and adhesive properties.
For selected process parameters as per Taguchi
method L9 orthogonal array design system, nine setsof simulation have been performed in Table 3 withthe purpose of optimizing process parameters. It isconsidered to be the result parameter and therefore,
the signal to noise ratio has been calculated for allnine experiments and the S/N ratios major effect wasplotted as shown in Fig. 7.

Response table for signal noise ratios: Larger isbetter

Level

Level

6

variance, where the observed variance was divided
into components attributable to different sources ofvariation in a particular variable. Anova provides astatistical test in its simplest form to determine
whether two or more population means are equal,
thus generalizing the t-test beyond two means.
5.1 Regression analysis: Flammability rate (V)versus Anti-flaming agent types, Anti-flaming
agent contents, Types of tackifiers

Analysis of variance
Table 7 Flammability rate (V) analysis of variance

Fig. 7 Plot for SN ratio

SourceDF

Adj SS

Adj MS

F-Value

P-Value

Regression

3

0.051683

0.017228

1.35

0.358

AFA

1

0.000417

0.000417

0.03

0.864

AFC

1

0.009600

0.009600

0.75

0.425

T

1

0.041667

0.041667

3.27

0.130

Error

5

0.063717

0.012743

Total

80.115400

Model summary
Table 8 Flammability rate (V) model summaryFig. 8 Plot for means data
The signal noise ratio response graph is given
in Fig. 8 and the best set of optimum parameters canbe determined by the level with highest signal noise
ratio by each factor which is A1B1C1.

Optimal Value

AFA

Phosphorus flame retardant

AFC

0.5 %

T

Hydrocarbon resin

R-sq

R-sq (adj)R-sq (pred)

0.112886

44.79 %

11.66 %

0.00 %

Coefficients
Table 9 Flammability rate (V) coefficients

Table 6 Optimal Value of Parameter
Parameter

S

Term

Coef

SE Coef

T-Value

P-ValueConstant

1.627

0.164

9.92

0.000

AFA

0.00830.0461

0.18

0.864

1.00

AFC

0.04000.0461

0.87

0.425

1.00

T

0.08330.0461

1.81

0.130

1.00

(5) Anova analysis

Regression equation

Variance of Analysis (ANOVA) was a collection of
statistical models and their related estimation techniques such as the variation between and between
groups used to evaluate group mean differences in asample. The anova was based on the law of total

Flammability rate (v) = 1.627 + 0.0083AFA +0.0400AFC + 0.0833T

7

VIF

Coefficients
Table 12 Flammability rate (V) coefficients
Term

Coef

SE

T-Value

P-Value

VIF

Coef
Constant

2.520

0.214

11.78

0.000

Anti-flaming-0.0933

0.0601

-1.55

0.181

1.00

0.04330.0601

0.72

0.503

1.00

-0.0700

0.0601

-1.16

0.297

1.00

agent types
Anti-flaming
agent contents

Fig. 9 Flammability rate (V) plot graph

Types oftackifier

5.2 Regression analysis: Peel strength (N) versus
Anti-flaming agent types, anti-flaming agent
contents, types of tackifiers

Regression equation
Peel strength (N) = 2.520 -0.0933AFA + 0.0433 AFC– 0.0700T.

Analysis of variance
Table 10 Peel strength (N) analysis of variance
SourceDF

Adj SS

Adj

F-Value

P-ValueMS
Regression

3

0.092930.03098

1.43

0.339

AFA

1

0.05227

0.05227

2.41

0.181

AFC

1

0.011270.01127

0.52

0.503

T

1

0.029400.02940

1.36

0.297

Error

5

0.10847

0.02169Total

80.20140

Fig.10 Peel strength (N) plot graph

Model summary
Table 11 Peel strength (N) model summary
S

R-sq

R-sq (adj)R-sq (pred)

0.147287

46.14 %

13.83 %

0.00 %

8

5.3 Regression analysis: Tack strength (N) versus
Anti-flaming agent types, anti-flaming agent
contents, types of tackifier
Analysis of variance
Table 13 Tack strength (N) analysis of variance
SourceDF

Adj SS

Adj MS

F-Valu

P-Va

e

lue

Regression

3

0.1411000.047033

1.25

0.385

AFA

1

0.077067

0.077067

2.05

0.212

AFC

1

0.006017

0.006017

0.16

0.706

T

1

0.058017

0.058017

1.54

0.269

Error

5

0.188189

0.037638

Total

8

0.329289

Fig. 11 Tack strength (N) plot graph
The analysis of variance (Anova) was used to determine the significance of the parameter. The larger
the F-value, the greater the effect on simulation
performance, and the smaller the P value, the greater
the significance of the parameter.
Analysis of variance (Anova) has been
conducted to analyze the larger the value of F-value,
the larger effect on the simulation performance andthe smaller the P value, the more significant to theparameter. It is safe to conclude that, the benefits offlammability rate, peel strength, and tack strength arecorrectly given a specific level of ignite or flame
spread resistance and best tackifier compounds will
help balance pressure sensitive adhesive and cohesive properties.

Model summary
Table 14 Tack strength (N) model summary
S

R-sq

R-sq (adj)R-sq (pred)

0.194005

42.85 %

8.56 %

0.00 %

Coefficients
Table 15 Flammability rate (V) coefficients
Term

Coef

SE

T-Value

P-Value

VIF

4. CONCLUSION

Coef
Constant

2.032

0.282

7.21

0.001

AFA

-0.1133

0.0792

-1.43

0.212

1.00

AFC

-0.03170.0792

-0.40

0.706

1.00

T

0.09830.0792

1.24

0.269

1.00

In this study, the best categories of anti-flaming agent
and mechanical properties of solvent free polyurethane based pressure sensitive adhesive have been
discovered. The results show that, to achieve theoptimal result for flammability, tack, and peel test,
each parameter has its own role. It can be concluded
that the optimum combination of parameter factors
for the solvent free polyurethane based pressure
sensitive adhesive is simulation number 1 which is
AFA1-AFC1-T1. The anti-flaming agent type is
phosphorus flame retardant, the anti-flaming agent
content is 0.5 %, and lastly the type of tackifier ishydrocarbon resin.It is also concluded that the typesof anti-flaming agent give a specific level of ignite or
flame spread resistance. The anti-flaming agent
content provides a particular level of flame spreadand the type of tackifier compound helps balancepressure sensitive adhesive and cohesive properties.

Regression equation
Tack strength (N) = 2.032 – 0.1133AFA – 0.0317
AFC + 0.0983T.

9

ACKNOWLEDGMENT
This research was supported by the 5th Research
Grant of th International Polyurethane Technology
Foundation.

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Adhesives from Palm Oil Based Resin-A Prepolymer Method.
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[9]Saravanakumar, K., Swapna, P., Nagaveni, P., Vani, P., & Pujitha, K. (2015). Transdermal Drug Delivery System: A Review
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ASTM D 2979-95: Standard Test Method for Pressure-Sensitive Tack of Adhesives Using an Inverted. Current,(Reapproved), 3–5. ASTM. (2001).

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ASTM D 330: Standard Test Method for Peel Adhesion ofPressure-Sensitive Tape. American Society for Testing andMaterials, 1–6. ASTM. (2003).
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