TECHNICAL INFORMATION
ADDITIVES FOR 1-PACK AND 2-PACKEPOXY ADHESIVES AND SEALANTS
AS-TI 5

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Additives for 1-pack and 2-pack epoxy adhesives and sealants

Contents
03 Introduction
04 Defoamers/air release agents
05 Rheology additives
14 Wetting and dispersing additives

03

Introduction
Compared with other joining processes, the use of adhesives
to join and seal material components allows considerable
versatility and various application possibilities. The adhesive
process is often superior to other production processes, and it
fulfills the requirements of a multitude of high-performance
applications.
Epoxy adhesives and sealants offer equally diverse application
possibilities, and are preferred in aviation, construction,
automotive and electrical industries. They have considerable
strength, provide good adhesion even on the most difficult of
substrates, and are highly chemically resistant.
However, in order to exploit their full potential, these products
must be manufactured using the utmost care and technicalexpertise. Alongside an optimum combination of raw materials,
additives play a major role in the production and optimizationof epoxy adhesives and sealants, e.g.:

Note
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• Ensuring producibility and quality consistency• Improving properties such as substrate wetting, defoaming andapplication parameters, and thereby simplifying application andincreasing efficiency• Increasing storage stability
BYK offers a multitude of additives for 2-pack and hot-cured
1-pack epoxy systems that guarantee and improve the efficiencyof these adhesive technologies.

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Additives for 1-pack and 2-pack epoxy adhesives and sealants

Defoamers/air release agents
Trapped air bubbles and the formation of foam represent a
major challenge in the production and application processesof epoxy formulations, especially with thick layers andsophisticated viscosity profiles.

resin and hardener components. For good efficiency, theadditive must have a specific incompatibility with the matrix.
When selecting these additives, it is necessary to consider agood balance between compatibility and efficiency.

Defoamer/air release agent recommendations for
1-pack and 2-pack epoxy formulations
Defoamer/air release agent base

Recommendation

The use of defoamers and air release agents prevents ordestroys the foam bubbles, resulting in improved processing,perfect surface properties and, in turn, optimized efficiency.

Defoamers and air release agents in 1-pack and 2-packepoxy systems can be divided into:

Silicone

BYK-1796
BYK-A 525
BYK-A 530

Polymer (silicone-free)

BYK-1790
BYK-A 501
BYK-A 535
BYK-A 550

Polymer/silicone

BYK-A 530

In doing so, air release agents help to transport any trapped
air to the surface. The subsequent destruction of the foam
bubbles at the surface is referred to as defoaming and isachieved by using the appropriate defoamer. Despite thedifferent terms, to a certain extent both products bringabout the same effects, which means that an air releaseagent also has a defoaming effect, and a defoamer canalso contribute towards the release of air.

• Modified polysiloxanes• Silicone-free polymer defoamers• Silicone modified polymer defoamers
Air release agents and defoamers are added to andincorporated into the respective components at the start ofproduction. This ensures the efficiency of these additives
throughout the production process, i.e. during production as
well as during transportation, the mixing process andapplication.

The efficiency of the defoamer and air release agent
depends on its compatibility with the adhesive or with theT. 01

Effect of a defoamer in
a 2-pack epoxy system

Effect of air release agents and defoamers

Air entrapment in the formulation:
The air release agent accelerates the migrationof the bubbles to the surface.

Reference

Foam on the surface:
The defoamer destabilizes the foam bubbles.

G. 01

Air release agent used in resin
components

G. 02

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Additives for 1-pack and 2-pack epoxy adhesives and sealants

Rheology additives
The rheological behavior of epoxy systems is a key parameter.
For example, a high viscosity is required in order to increase
the sag resistance and stabilization of fillers, while the
manufacturing properties, miscibility and air release arepositively influenced by a low viscosity. BYK offers a variety
of different rheology additives in order to tailor therheological profile of the epoxy systems to the application.
These include:• Solid rheology additives• Liquid rheology additives• Rheology boosters

GARAMITE for 1-pack and 2-pack epoxy systems
GARAMITE is a solid, powdered rheology additive which
specifically influences the rheology profile of the epoxy
system. It comprises a combination of phyllosilicates, thesurfaces of which have been organically modified. These
modifications control the efficiency in varying polarities andin different systems. The high bulk density of GARAMITE
reduces the formation of dust and simplifies processing.

The advantages of using GARAMITE:

Composition of GARAMITE• Strong shear thinning viscosity profile• Prevents the settling of solids• Highly efficient•	High stability and very good ridge formation•	Easy application of the adhesive and sealant fromcartridges and dosing units• High bulk density, low dusting•	Easy incorporation, no special activation required•	Increased efficiency with boosters, as needed
GARAMITE-1958 and GARAMITE-7305 are products whichhave been specially developed for epoxy systems which
influence the flow behavior of both the resin and thehardener components.

G. 03

Improving sag resistance when applying a 2-pack epoxy system

Without additive
2-pack epoxy system, (bisphenol A resin + amido-amine hardener)

GARAMITE used in resin component
G. 04

Additives for 1-pack and 2-pack epoxy adhesives and sealants / Rheology additives

Liquid rheology additives in epoxy systems can be used inboth the resin and the hardener components. They form athree-dimensional network, thus optimizing the settling offillers and the anti-sag properties of components whenapplied. Their advantage lies in simple dosing and thepossibility to incorporate the additives even after production(post-adding).
RHEOBYK-410 and RHEOBYK-7410 ET are urea-basedrheology additives that prevent the formation of
sedimentation in filled epoxy systems, and improve the sag
resistance. The products increase the viscosity especially at
low shear rates, and barely influence the viscosity in thehigh shear range.
RHEOBYK-430 is based on a urea-modified, medium polarity
polyamide. The settling behavior, especially in filled aminic
hardener components, can be improved due to theadditive’s impact on the pseudoplastic flow behavior.

Rheology control – rheology boosters andviscosity control technology
2-pack epoxy systems are used in high-performance
applications in the automotive, aviation and constructionindustries. One of the most important parameters is thestability of the reactive mixture after application. It is only asufficiently high sag resistance after mixing the componentsthat permits vertical or above-head applications.

Booster effectMarket standard

Solution with BYK additives

Viscosity decreases
considerably during mixing

Resin withhydrophobic silica

Hardener

Mixtureresin/hardener

Viscosity

Liquid rheology additives for 1-pack and2-pack epoxy systems

Viscosity

06

Booster effectResin withhydrophilic silica

Hardener + booster

Mixtureresin/hardenerG. 05

However, when you consider the process steps of the
production, mixing and application of the system, asignificantly lower viscosity is preferred: production isfacilitated, the components are easy to pump, they mix
more easily and more thoroughly, and can be applied using
less pressure.

Furthermore, the storage stability is improved, and the useof hydrophilic instead of hydrophobic silica enable theproduction costs to be reduced too.

At first this contrast appears to be impossible to resolve, assuch strong shear thinning effects and viscosity increases
cannot be achieved using conventional rheology additives.

Rheology boosters work in combination with modified
phyllosilicates (e.g. GARAMITE-7305) or pyrogenic silicas.
They are added to the hardener and only when mixed arethey combined with the solid thixotropic agents which arelocated in the resin component. Here, they strengthen thethree-dimensional network of the rheology additive andbring about a significant increase in viscosity comparedwith a formulation that does not contain a booster.

With the options of rheology boosters and “viscosity control
technology”, the viscosity can be influenced in precisely thecorrect process steps: during production and processing,low viscosities are possible, and then only after mixing will
the viscosity increase immediately, thereby resulting inoutstanding sag resistance.

Rheology boosters for 2-pack epoxy systems

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Additives for 1-pack and 2-pack epoxy adhesives and sealants / Rheology additives

Benefits

Working principle of Thixboosters

Generally speaking, the use of a booster increases theefficiency of fumed silica or phyllosilicates as soon as thesolid rheology additive and the booster come into contact
by mixing together the A and the B components. This
enables hydrophobic silica to be replaced with hydrophilic
silica. The lower efficiency of hydrophilic silica reduces theviscosity of the resin components and improves the mixing
and application properties. After mixing, the booster
increases the efficiency and the viscosity rises, which results
in an outstanding sag resistance.

BYK Thixboosters

Fumed silica or GARAMITE

Advantage of storage stability

Viscosity comparison of a resin with hydrophobic and hydrophilic silica
Viscosity η (Pa·s)

In many cases, epoxy formulations with (hydrophilic) silica
are not storage-stable. The combination of hydrophilic silica
with BYK rheology boosters prevents the loss in efficiency
during storage so that the individual components can beused to create sag resistant applications, even after a long
period of storage.

G. 06

1,200
1,100

Part A

Marketstandard

Formulation
with BYK

Bisphenol A resin

65

65

Hydrophobic silica

3

1,000
900
800
700

Hydrophilic silica

600

3

500
400
300
200
100
0
0.1

1

10

100

1,000
Shear rate γ (1/s)

Market standard  

Formulation with BYK

G. 07

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Additives for 1-pack and 2-pack epoxy adhesives and sealants / Rheology additives

Comparison of silicas with Thixboosters
Market standardhydrophobic silica

Referencehydrophilic silica

BYK recommendation ofhydrophilic silica + Thixbooster

Fresh

Aged

G. 08

Additives for 1-pack and 2-pack epoxy adhesives and sealants / Rheology additives

Tensile strength

Mechanics
The use of BYK rheology boosters in 2-pack epoxy adhesives
has no measurable influence on the mechanical propertiesof the systems. The tensile strength of overlapping, bonded
steel test specimens is comparable with the market standard.

Sag resistance when curing 1-pack epoxy systems
Thermally cured 1-pack epoxy adhesives must have high sag
resistance across the entire application process. The uncured
adhesives are applied, the joined parts washed and theadhesive bond cured in the furnace.

Tensile strength (MPa)

09

20

15

10

5

0
Market standard

BoostedRHEOBYK-R 606

BoostedRHEOBYK-R 607

The combination of hydrophilic silica with the rheology
booster RHEOBYK-R 606 enables the application ofsag resistant 1-pack epoxy systems without the loss of
sag resistance during curing.

BoostedBYK-P 2720
G. 09

Application and sag resistance

1-Pack epoxy adhesive formulation
Raw material

Market standard(parts)

BYK recommendation(parts)

Bisphenol – A resin

100

100

Filler150

150

Hydrophobic silica

3Market standard(hydrophobic silica)

Hydrophilic silica

3

Thixbooster
RHEOBYK-R 606

0.6(20 % on fumed silica)

Hardener

6

6

Accelerator

2

2
T. 02

Cured at 130 °C,
30 minBYK recommendation(hydrophilic silica+ RHEOBYK-R 606)

G. 10

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Additives for 1-pack and 2-pack epoxy adhesives and sealants / Rheology additives

Viscosity

The mechanics of the thermally cured 1-pack epoxy
adhesives are not influenced by the modification with BYK
boosters. The tensile strength of overlapping, adhered steel
test specimens is comparable with the market standard.

The viscosity profile of 1-pack epoxy formulations can be
specifically adjusted by combining hydrophilic silica withRHEOBYK-R 606.

Tensile strength

Comparison of different rheology profiles

35

Viscosity η (Pa·s)

Tensile strength (MPa)

Mechanics

30
25
20

160,000
140,000
120,000
100,0015
80,00010

60,0005
040,000Market standard

Reference

RHEOBYK-R 606

0

10

20

30

40

50
rpm

G. 11

1.2 % hydrophilic silica + RHEOBYK-R 606
1.2 % hydrophobic silica
0.6 % hydrophilic silica + RHEOBYK-R 606
3 % hydrophilic silica

G. 12

Additives for 1-pack and 2-pack epoxy adhesives and sealants / Rheology additives

high

The “viscosity control technology” (VCT) is a newtechnology which is based on a combination of two
process additives which are specially aligned with eachother. With their help it is possible to adjust both theviscosity of the A and the B components. There is anadditive for the resin system (Thixbreaker) and an additivethat has been developed for the hardener (Thixbooster).
The Thixbreaker has the task of reducing the viscosity of
the resin component to a desired extent. The Thixbooster
is used in the hardener and doesn’t change the viscosity
provided there is no silica present. Adding silica at thispoint can increase the efficiency. When the components
meet, the interaction of the VCT additive brings about asignificant increase in the viscosity (G. 13). This newconcept of “viscosity control technology” has very broad
uses across the entire value chain (G. 18).

Comparison of market standard and BYK solution with VCTMarket standard

Desired application viscosity

BYK solution

Viscosity

Viscosity control technology (VCT)
for 2-pack epoxides

low

11

Component A• Epoxy resin• Hydrophobic silica

Component B• Hardener• Hydrophilic silica

Mixed system

Component A• Epoxy resin• Thixbreaker• Hydrophilic silica

Component B• Hardener• Thixbooster

G. 13

Viscosity in production

Viscosity at application

G. 14

G. 15

Additives for 1-pack and 2-pack epoxy adhesives and sealants / Rheology additives

Thixbreaker – use in the resin component
The conventional hydrophobic silica in the resin component
is replaced by hydrophilic silica. The Thixbreaker is added to
the resin component and blocks the structural build-up of
the silica network – the viscosity of the resin component
is low.

Adapting the resin to the hardener viscosity using BYK-P 2710
Viscosity (Pa·s)

12

100
80

Resin

60
40
Hardener

20
0
0

40

60

80

100
% BYK-P 2710 based on silica
G. 16

The Thixbooster is added to the hardener component andcan, if required, be combined with hydrophilic silica. After
mixing the components, the Thixbooster brings about thedevelopment of the three-dimensional network, thereby
creating a sag resistant application.

Adapting the hardener to the resin viscosity using BYK-P 2710
Viscosity (Pa·s)

Thixbooster – use in the hardener component

100
Hardener
80

Resin

60
40
20
0
0

10

20

30

40

50

% BYK-P 2720 based on the silica
G. 17

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Additives for 1-pack and 2-pack epoxy adhesives and sealants / Rheology additives

Formulation

Value chain

Different mixing viscosities of the resin and hardenercomponents can be adapted precisely to one another.

Formulation

Manufacture

Transportation

Application

Manufacture
G. 18

VCT enables the use of the same apparatus for the resin
and the hardener components. A simple dissolver can beused to produce the components. Cost-effective hydrophilic
silica can be used as an alternative to hydrophobic silica.

Recommended rheology additives, boosters and VCT for 1-pack and 2-pack epoxy systems
Application

1-pack epoxy

2-pack epoxy

Anti-settling

CLAYTONE-40
GARAMITE-1958
GARAMITE-7305
RHEOBYK-430
RHEOBYK-7410 ET
RHEOBYK-D 410

CLAYTONE-40
GARAMITE-1958
GARAMITE-7305
RHEOBYK-430
RHEOBYK-7410 ET
RHEOBYK-D 410

Sag resistance

CLAYTONE-40
GARAMITE-1958
GARAMITE-7305
RHEOBYK-100
RHEOBYK-7590

CLAYTONE-40
GARAMITE-1958
GARAMITE-7305
RHEOBYK-100
RHEOBYK-7590

Booster

RHEOBYK-R 606

BYK-P 2720
RHEOBYK-7405
RHEOBYK-R 607

VCT-

BYK-P 2710
BYK-P 2720

Transportation
Pumpable resin and hardener components can be transported
in IBCs and bulk containers. The low viscosity also enables
pumping from pails and drums.

Application
Mixing the two low-viscosity components results in a
sag resistant application. Low mixing viscosities simplify
the dosage and processing of 2-pack systems.

T. 03

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Additives for 1-pack and 2-pack epoxy adhesives and sealants

Wetting and dispersing additives
Optimizing an epoxy system: lower viscosity or greater filler amount
Increasing the filler amount while maintaining the viscosity

Viscosity (Pa·s)

When formulating 1-pack and 2-pack epoxy adhesives andsealants, the easy incorporation and even distribution ofsolid fillers and pigments in the liquid or highly viscous resinand hardener matrix is essential. This is the only way toensure optimized and fast production, and consistent quality
and performance.

Reduction of viscosity

The use of wetting and dispersing additives also enables theviscosity to be reduced. This can achieve either better
processing or an increase in while maintaining the viscosity.
However, the lower viscosities can also intensify settling,which is countered with the use of rheology additives.
Alternatively, it is possible to use controlled flocculating
wetting and dispersing additives, which prevent settling by
network formation.

Filler amount (phr)Reference  

G. 19

Wetting and dispersing additive

Influence of wetting and dispersing additives on the viscosity
Viscosity (Pa·s)

When selecting wetting and dispersing additives, you must
be mindful of any reactivity of the additive with the epoxy
system. BYK offers special wetting and dispersing additives
which are stable in epoxy systems and therefore have noinfluence on the storage stability of the formulated
components (G. 22).

Soft settlement

Hard settlement

Shear rate
Controlled flocculating  

Flocculating  

Deflocculating

G. 20

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Additives for 1-pack and 2-pack epoxy adhesives and sealants / Wetting and dispersing additives

Optimizing an epoxy system: lower viscosity or higher filler amount

Viscosity reduction by using
wetting and dispersing additives

Control – no additive

Increasing the filler amount by using
wetting and dispersing additives

G. 21

Application

Recommendation

Strong viscosity reduction

BYK-9076
BYK-W 969
BYK-W 985
BYK-W 996
BYK-W 9010
BYK-W 9011
DISPERBYK-118
DISPERBYK-2152

Viscosity reduction andanti-settling

BYK-W 940
BYK-W 966
BYK-W 980

Rheology additives thatcan be combined with wetting
and dispersing additives –anti-settling

RHEOBYK-7410 ET
GARAMITE-1958
GARAMITE-7305

Storage stability
Viscosity (Pa·s)

Wetting and dispersing additive recommendations for
1-pack and 2-pack epoxy adhesives and sealants

400
350
300
250
200
1 day

Reference  

T. 03

1 weekWetting and dispersing additive

2 weeks

3 weeks

4 weeks

8 weeksG. 22

07/2024
AS-TI 5Your 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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