TECHNICAL INFORMATION
ADDITIVES FOR AQUEOUS
PRESSURE-SENSITIVE ADHESIVESAS-TI 6

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Additives for aqueous pressure-sensitive adhesives

Contents
03 Introduction
05 Defoamers for pressure-sensitive adhesives
09 Surface additives for pressure-sensitive adhesives
12 Combination of defoamers and surface additives for pressure-sensitive adhesives
13 Influence of defoamers and surface additives on mechanical properties
14 Rheology additives for pressure-sensitive adhesives

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Introduction
Pressure-sensitive adhesives are used to produce adhesive
tapes and self-adhesive labels. They are characterized by theirlasting adhesion, which enables permanent or detachable
adhesive connections to be formed with light contactpressure.
Typical applications for aqueous pressure-sensitive adhesive
systems range from adhesive tapes for the packaging industry
to removable labels and permanent adhesive products forbonding mirrors or skirting boards. Aqueous pressuresensitive adhesive systems are based on acrylate, vinyl
acetate-ethylene (VAE), or polyurethane dispersions.

Note
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BYK additives optimize the production and application
process of aqueous pressure-sensitive adhesives, and improve
the application properties.
Defoamers reduce or avoid the formation of foam during
production and application processes.
Surface additives optimize the wetting on the pressuresensitive adhesive carrier and the separating foil.
Rheology additives adjust the flow behavior of aqueous
dispersions, enabling spatter-free application and goodwetting on the carrier.

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Additives for aqueous pressure-sensitive adhesives

Effect of additives in the production process

Surface additive
Rheology additive
Process additive

Defoamer

1
Defoamer
Surface additive
Rheology additive

4

3

5
6

2

1

Production of the aqueous pressure-sensitive adhesive dispersion
2

Providing of the carrier3

Application of the dispersion on the carrier

4

Evaporation of the water

5

Heating

6Winding the PSA product


G. 01

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Additives for aqueous pressure-sensitive adhesives

Defoamers for pressure-sensitive adhesives
Aqueous pressure-sensitive adhesive dispersions can develop
foam during the mixing and production process, impeding
mixing and extending the transfer and filling times. Foam
can also form when processing with spray, nozzle, or roller
applications. This formation can lead to surface defects,
craters, and a reduction in adhesion.
Defoamers prevent and destroy the foam bubbles, enabling
improved processing, a perfect surface, and optimum
product properties.

Creation of foam and effect of defoamers
The generation of stable foam bubbles requires foamstabilizing substances to be present in the liquid phase.
Generally speaking, these are surface-active substances(surfactants) that are characterized by having hydrophobic
and hydrophilic chemical domains in the molecule. Due tothis structure, they orientate themselves at the interfaces theliquid and the gaseous phase, reduce the surface tension,

Foam stabilization by surfactants

G. 02

and create the requirements for a stable foam. Everyaqueous pressure-sensitive adhesive dispersion contains a
multitude of such surface-active substances that encourage
foam formation and stabilize the foam.
Defoamers are used to prevent foam formation or todestabilize foam bubbles that arise despite the presence offoam-stabilizing substances, and to destroy foam as quickly
as possible.

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Additives for aqueous pressure-sensitive adhesives / Defoamers for pressure-sensitive adhesives

A key feature of all defoamers is their targeted andcontrolled incompatibility with the medium that is tobe defoamed. A defoamer that is too compatible does not
migrate into the foam lamella specifically, but rather isdistributed evenly in the pressure-sensitive adhesive film;
the defoaming effect is either low or non-existent.
Too much incompatibility causes defects such as turbidity or
cratering. Choosing the correct defoamer is a balancing act
between compatibility and incompatibility. The term“incompatibility” generally does not mean that a reductionin adhesion can be expected after the pressure-sensitiveadhesive has been applied. When using a suitable defoamer,
and provided the recommendations for incorporation anddosage are followed, there is no reduction in the adhesionor performance of the pressure-sensitive adhesive.
To adjust the optimum defoaming in aqueous pressuresensitive adhesive dispersions, differentiation is madebetween three defoamer groups:• Mineral oil defoamers• Silicone defoamers• Polymer defoamers

Mineral oil defoamers consist of approximately 85–95 %mineral oil and 1–3 % hydrophobic particles. They canalso contain emulsifiers, biocides, and other performanceenhancing ingredients such as modified polysiloxanes.
Aliphatic mineral oils are used as the carrier oil.
Silicone defoamers are defoamer fluids with a particularly
low surface tension that contain polysiloxanes as theprimary active substance. However, when selecting apolysiloxane, its structure is critical. For instance, the relatively
short-chained polysiloxanes that are used as silicone surface
additives stabilize foam but have no defoaming effect.
Whether a polysiloxane has a defoaming or foam-stabilizing
effect depends on its compatibility and solubility in themedium: only incompatible and insoluble polysiloxanes
have a defoaming effect.
Polymer defoamers also have a defoaming effect due
to their incompatibility. Finding the right balance between“incompatible” and “compatible” is achieved by making
selective changes to the polarity and molecular weight(molecular weight distribution) of the polymer structures.
In polymeric defoamers for aqueous systems, hydrophobic
particles are used to enhance the defoaming efficiency.
Chemically, the particles are based on hydrophobic silicas,
polyurea, or polyamide.

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Additives for aqueous pressure-sensitive adhesives / Defoamers for pressure-sensitive adhesives

The foam volume is assessed. The following graphics
provide an overview of typical defoamers and theirefficiency in aqueous dispersions.

To evaluate the efficiency of the defoamer in the specificpressure-sensitive adhesive dispersions, the systems are
modified using defoamers and then precisely foamed.

Foam volume (mm)Defoamers for acrylic pressure-sensitive adhesive dispersions
30
25
20
15
10
5
0
Without defoamer

Acrylate dispersion 1  

BYK-016

Acrylate dispersion 2  

BYK-022

BYK-028

Polymer defoamer  

BYK-037

Silicone defoamer  

BYK-044

BYK-093

BYK-094

BYK-1640

BYK-1719

BYK-1740*

G. 03

Mineral oil defoamer* From bio-based raw materials

Test method: The defoamer is incorporated in the acrylate
dispersion with a dissolver. The modified dispersion is thenfoamed using a dissolver disc at a defined speed and for adefined period of time. Directly after foaming, the initial
filling height is compared and assessed against the foamheight. The influence on the speed of foam destruction ismeasured by reassessing the foam height after a defined
period of time. The parameters such as agitation speed,agitation duration, choice of agitating disk, and receptacle
used are adapted according to the system that is to betested.

Evaluation: The effectiveness and choice of defoamer
depends on the system. For example, the polymer defoamer
BYK-1640 is highly effective in acrylate dispersion 1,
whereas the foam height in acrylate dispersion 2 is higher.
In both test systems, BYK-094 and BYK-044 show very
effective defoaming. Good efficiency of the defoamer
depends on targeted incompatibility of the additives
in the system. A strong defoaming effect with too muchincompatibility can cause surface defects or problems withthe substrate wetting. It is important to assess and exclude
this by carrying out tests. Surface defects can also be
minimized by modification with surface additives.

Food Contact
With pressure-sensitive adhesive dispersions, especiallyfor packaging and label applications, both performanceand compliance with legal provisions must be ensured.
BYK provides a multitude of additives that are suitable fordirect food contact. Please contact us with any food contact
legal status queries: foodcontact.byk@altana.com
www.byk.com/foodcontact

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Additives for aqueous pressure-sensitive adhesives / Defoamers for pressure-sensitive adhesives

Foam volume (mm)Defoamers for VAE pressure-sensitive adhesive dispersions
30
25
20
15
10
5
0
Control

BYK-014*

Polymer defoamer  

Silicone defoamer

BYK-016

BYK-022

BYK-094

BYK-1640

BYK-1650

BYK-1723

BYK-1724

BYK-1740*

BYK-1745*

BYK-1786

G. 04* From bio-based raw materials

Acrylate dispersion

Without defoamer

Defoamer recommendations for aqueous pressure-sensitive adhesive dispersions
Defoamer class

Recommendations foracrylic dispersions

Recommendations for
VAE dispersions

Recommendations forpolyurethane dispersions

Polymer defoamers

BYK-012
BYK-014*
BYK-016
BYK-1640
BYK-1740*
BYK-1745*

BYK-014*
BYK-016
BYK-1640
BYK-1740*
BYK-1745*

BYK-014*
BYK-1640
BYK-1641

Silicone defoamers

BYK-022
BYK-023
BYK-028
BYK-093
BYK-094
BYK-1611
BYK-1641
BYK-1650
BYK-1723
BYK-1724

BYK-022
BYK-094
BYK-1650
BYK-1723
BYK-1724
BYK-1786

BYK-022
BYK-028
BYK-092
BYK-093
BYK-094
BYK-1611
BYK-1724

Mineral oil defoamers

BYK-037
BYK-039
BYK-1630-

BYK-039

With BYK defoamer
G. 05* From bio-based raw materials

T. 01

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Additives for aqueous pressure-sensitive adhesives

Surface additives for pressure-sensitive adhesives
The production of pressure-sensitive adhesive products suchas labels and adhesive tapes requires good wetting and goodleveling of the dispersion on the carrier. Surface defects on
the applied film are undesirable as they affect the visualappearance and the adhesion. Typical surface defects arepoor substrate wetting, cratering, and insufficient leveling.
A key parameter is the surface tension or surface tension
differences between the materials involved, which lead tosurface defects. To avoid these faults, additives are usedthat influence the surface tension of the adhesive dispersion
and minimize surface tension differences. These additives
are mostly based on polysiloxanes (silicones), which –depending on their chemical structure – reduce the surface
tension of the dispersion. Alongside an improvement in thesubstrate wetting and outstanding anti-cratering properties,
polysiloxane surface additives can also improve the surface
slip of the pressure-sensitive adhesive film.

Generally speaking, good substrate wetting is achieved assoon as the surface tension of the dispersion is lower than
the surface energy of the substrate that is to be wetted.

of the dispersion (dynamic surface tension). In order tocharacterize the dispersion in full, both measuring principles
should be applied.

The surface tension of the liquid pressure-sensitive adhesive
dispersion can be determined statically by the Du Noüyring method and dynamically using a bubble pressure
tensiometer. The test methods can be seen in G. 07.

The surface energy of the substrate that is to be wetted
is determined by evaluating the contact angle of different
liquids on the respective substrate. In doing so, the contact
angle indicates the wettability of the substrate.

With the ring method, no energy is applied to the liquid
during the measurement and the surface-active substances
involved are in a thermodynamic equilibrium. This represents
the state after application of the dispersion (static surface
tension). When measuring using a bubble pressure
tensiometer, the measuring process is based on continuously
and rapidly forming gas bubbles, which is how this method
determines the surface tension for, e.g. the application

Measuring the surface tension

Wetting as a function of adhesive and cohesive forces
LiquidAdhesive forces

Cohesive forces

Adhesive forces

Substrate
Wetting: Adhesion > cohesion
Good substrate wetting: σliquid < σsubstrate
Ring method
G. 06

Bubble pressure tensiometer
G. 07

Additives for aqueous pressure-sensitive adhesives / Surface additives for pressure-sensitive adhesives

Good wetting of pressure-sensitive adhesive dispersions on
the respective substrates is essential. Polysiloxane-based
surface additives reduce the surface tension of the pressuresensitive adhesive dispersions and therefore enable a defectand crater-free draw down even on substrates that are
difficult to wet, such as PET or polyolefin-based plastics.
G. 08 provides an overview of the efficiency of different
surface additives for pressure-sensitive adhesive applications.

PSA dispersion – modified with 0.2 % surface additive
Static surface tension(mN/m)

10

40
35
30
25
20
15
10

A significant reduction in the surface tension even at alow dosage and with good spreading on the low-energy
substrates is achieved by modification with special
trisiloxane-based surface additives. The effect is shownin G.11.

50
Without
additive
Polymeric silicone

BYK-333

Trisiloxane

Silicone-free variant of BYK-3400

The surface tension can beadapted by adjusting the dosage
to the required level

29 mN/m

30 mN/m

30 mN/m

BYK-3451

BYK-3455

BYK-3410

BYK-3400

BYK-349

G. 08

Silicone surfactant with polyether modification
Standard silicone surfactant

Dependency of static surface tension
on the addition of silicone surfactants

Application of a PSA dispersion

Static surface
tension (mN/m)

38 mN/m

BYK-3450

39
37
35
33
31
29
27
25
0

Without additive
G. 09

0.05

With surface additive

0.1

0.2

0.3

0.4

0.5

Addition of surface additive (%)
G. 10Standard silicone surfactant
BYK-3450
BYK-3451

G. 11

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Additives for aqueous pressure-sensitive adhesives / Surface additives for pressure-sensitive adhesives(mN/m)

Dynamic surface tension depending on thefrequency, 0.2 % additive addition

Surface wetting on a silicone paper

40

30

20
0.2

1

2

3

4

5

6

7

8

9

10
Frequency (Hz)low

BYK-345  “Age” of the surface

BYK-349  

BYK-DYNWET 800

The dynamic surface tension is essential for fast application
processes, as the interfaces are generated very quickly.
Alongside the static surface tension, the kinetics of theinterface formation also have a significant influence.
BYK-DYNWET 800 creates a considerable reduction insurface tension across the entire kinetics of the interface
formation.

highInsufficient wetting without
surface additive

Optimum wetting with
BYK surface additive

G. 12

G. 13

Defoamer recommendations for aqueouspressure-sensitive adhesive dispersions
Application

Recommendations

Reduction of static surface tension

BYK-348
BYK-349
BYK-3400
BYK-3410
BYK-3450
BYK-3451
BYK-3455

Reduction of dynamic surface tension

BYK-3450
BYK-3451
BYK-DYNWET 800
T. 02

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Additives for aqueous pressure-sensitive adhesives

Combination of defoamers and surface additives for pressure-sensitive adhesives

35

32

30

30

25

28

20
26
15
24

10

Typical additive combinations for optimum pressuresensitive adhesive dispersion properties can be seen
in T. 03.

22

5

20

0
Control

Typical additive combinations

Surface tension (mN/m)

The efficiency of the defoamer and surface additives, andthe targeted and necessary incompatibility of the defoaming
additives, depends on the system. The evaluation of suitablesystem-specific additive combinations is required (G. 14).

Reduction in surface tension and foam stabilizationby combination with defoamers
Foam volume (ml)For optimum production, filling and application of pressuresensitive adhesive dispersions, it is often necessary to use acombination of surface additives and defoamers. Due totheir incompatibility, defoamers can encourage surface
defects, while specific surface additives can promote thestabilization of foam. Combining the two additive classes
can address both defect causes and achieve an application
with both good leveling and the absence of foam.

0.2 % BYK-014

0.2 % BYK-014 + 0.5 % BYK-3400

G. 14

Defoamer

Surface additive

BYK-014
BYK-016
BYK-094
BYK-1640
BYK-1740
BYK-1745

BYK-349
BYK-3400
BYK-3410
BYK-3450
BYK-3451
T. 03

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Additives for aqueous pressure-sensitive adhesives

Influence of defoamers and surface additives on mechanical properties
Essential assessment criteria for pressure-sensitive adhesives
are adhesion testing in a 180° peel test and the test ofshear strength. The process-optimized modification of theaqueous pressure-sensitive adhesive dispersions with surface
additives and defoamers enables defect-free substrate
wetting, preventing technical adhesive defects. It mustalso be checked whether necessary incompatibilities of the

defoamer in the binder matrix will influence the adhesion.
G. 15 shows that the peel strength of an aqueous acrylatepressure-sensitive adhesive is not influenced by modification
with defoamers. The defined incompatibility of the defoamer
does not have a negative impact on the mechanics of theadhesive bond.

180° peel test

180° peel strength (N/25 mm)

No influence of defoamers on the peel strength

0.1 %

0.3 %

0.5 %

0.7 %
Defoamer addition (%)

Control  

BYK-094  

BYK-1640  

BYK-037

G. 15

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Additives for aqueous pressure-sensitive adhesives

Rheology additives for pressure-sensitive adhesives

If, however, this shear thinning effect is too strong, theviscosity during application is reduced to such an extent thatspattering and other undesirable effects can occur. By using
a rheology additive for the high shear range, also referred
to as a “Newtonian thickener”, this effect can be avoided.
In the low shear range, the additive increases the viscosity
only slightly; but in the high shear range, it increases theviscosity considerably. This increased viscosity level at highshear forces can significantly reduce or even completely
prevent spraying when applying.

ICIHigh viscosity in the low shear range prevents the settlingof solids and any phase formation of different formulation
components. Furthermore, wetting of the dispersion
adhesives on the pressure-sensitive adhesive carrier is
optimized. When applying high shear forces, e.g. during
stirring, pumping, and processing, the viscosity is reduced,
which ensures good applicability and processing.

Mode of action of associative thickenersη (Pa·s)

When formulating pressure-sensitive adhesive dispersions,defined rheology behavior is desired.

10

1
0.01

0.1

1.0

1000

10000
Shear rate D (1/s)

Low shearing

Dispersion (control)
RHEOBYK “H” (pseudoplastic thickener for low/medium shear ranges)
RHEOBYK “L” and “T” (thickener for the high shear range)

High shearing

G. 16

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Additives for aqueous pressure-sensitive adhesives / Rheology additives for pressure-sensitive adhesives

An increased viscosity across the entire shear range with
Newtonian flow behavior improves the anti-spattering effectat high application speeds. G. 17 shows the spattering
behavior of an acrylate pressure-sensitive adhesive
dispersion with no additive on the left and 0.3 % additionof a high-shear thickener on the right.

Reducing spattering during application

Without additive

0.3 % high shear thickener
G. 17

Rheology additive recommendations for pressure-sensitive adhesive dispersions
Newtonian rheology behavior/high-shear thickener

Pseudoplastic rheology behavior/
medium-shear thickener

Pseudoplastic rheology behavior/
low-shear thickener

RHEOBYK-7690
RHEOBYK-L 1400 VF
RHEOBYK-T 1000 VF
RHEOBYK-T 1010 VF

RHEOBYK-7670
RHEOBYK-M 2600 VF

RHEOBYK-7650
RHEOBYK-H 3300 VF
RHEOBYK-H 7500 VF
T. 04

07/2024
AS-TI 6Your local
contact

BYK-Chemie GmbH
Abelstraße 4546483 Wesel
GermanyTel +49 281 670-0
Fax +49 281 65735
info@byk.com
www.byk.com

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herein and data or information set forth, or that such products, data or information may be used without infringing intellectual property rights ofthird parties. Any information about suitability, use or application of the products is non-binding and does not constitute a commitment regarding
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