TECHNICAL INFORMATIONSOLVENT-FREE AND SOLVENT-BORNE FLOOR COATINGS

FL-TI 1

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Floor coatings

Contents
03 Introduction
05 Viscosity reduction and/or pigment stabilization
07 Storage stability
09 Defoaming /air release
12 Optimization of the surface
14 Troubleshooting for floor coatings

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Floor coatings

Introduction
All around the world, liquid polymer coatings are becoming an
increasingly popular finish for floors. While they were previously
only found in warehouses and production halls, they can now befound in shopping centers, schools and hospitals. More recently,
these coatings have also become available to end customers,
whether for decorative purposes in bathrooms or for recoating
the old screed in the garage.
Epoxy resin systems are by far the most commonly used floor
coating. The success of this technology is predominantly basedon the fact that these floor coatings are quick to install, easy toclean and very resistant.

As the systems have begun to gain popularity in commercial sectors,
the production of the coatings is being subjected to increasingly
strict regulations, for example in relation to volatile organic
compounds (VOC). For this reason, it is becoming increasingly
important to develop formulations that contain little to no solvents.
However, solvent-free systems are much more difficult to handle
during manufacturing and application processes, due to their highlevels of inherent viscosity and reactivity.
For this reason, a variety of additives are now used to simplify thehandling of the systems and enable consistently reproducible results
to be achieved.
Suggested additives for the floor coatings market can be found in
the “Additives for floor coatings” (FL-AG 1) brochure or atwww.byk.com/en/markets/floor-coatings.

Note
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Floor coatings / Introduction

Different floor systems and their properties
Penetrating primer

Primer filler for leveling out
unevenness

Self-leveling coating

Top coat/sealant(clear or pigmented)

Film thickness

0.2–0.3 mm

1–6 mm

1–3 mm

0.06–0.1 mm

Yield≈ 0.1–0.2 kg/m²(depending on the substrate)

At 1 mm: 0.8–1.6 kg/m²

At 1 mm: ≈ 1.5 kg/m²≈ 0.1–0.6 kg/m²

Application/function

Sealing the substrate,binding loose particles and improving the adhesion of subsequent coatings

Sealing pores and levelingthe surface

Mechanical and chemical resistance,
visual appearance, anti-static properties, slip
resistanceAbrasion and scratch resistance, UV stability,
visual appearance, slip resistance

Systems used

Low-molecular epoxy systems

Solvent-free systems based on epoxy or
polyurethane resins• Solvent-free systems based on
epoxy or polyurethane resins• Methacrylate systems• Aqueous epoxy resin formulations• Epoxy- and polyurethane-based
solvent-free systems• Polyaspartic systems• 	Methacrylate systems• Aqueous epoxy or polyurethane systems• Aqueous acrylate systems (1-pack)

Requirements• Good substrate wetting• No foam bubbles•G ood penetration into the substrate• Good substrate wetting• Low viscosity• Good storage stability• No foam bubbles• Good leveling• Good substrate wetting• Low viscosity• No flooding/floating of pigments• Good storage stability• No foam bubbles• Good leveling• Good substrate wetting• Low viscosity• No flooding/floating of pigments• Good storage stability• No foam bubbles• Good leveling• High transparency in clear systems
T. 01

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Floor coatings

Viscosity reduction and/or
pigment stabilization
Due to their high solids content and inherent viscosity, floor
systems have a tendency to stabilize foam and have poorleveling properties. Many resins that are used in this sector
also have poor pigment wetting properties. This can often
lead to pigment separation, Bénard cells or color fluctuations.
On large surfaces, it is particularly important to look out for
Bénard cells, as they are a sign of poor pigment stabilization
and are caused by turbulence, settling of the pigments/fillers
and the increase in viscosity. Controlled flocculating anddeflocculating wetting and dispersing agents can be used toprevent this.
These additives are particularly suitable for use with highly
filled primers or leveling primers. These coatings frequently
contain lots of fillers and require good penetration
properties. For epoxy and polyurethane coatings, products
such as BYK-P 104 S are ideal in this case. This productfamily creates a positive effect with regard to the color
stability and improves flooding/floating.

Rub-up test used tocheck for possible
color differences

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Floor coatings / Viscosity reduction and/or pigment stabilization

Highly filled, self-leveling top coatings and roller coatingsrequire excellent pigment stabilization of inorganic andorganic pigments and a higher level of gloss.
The best results are often provided by additives with amine
pigment-affinic groups. Nevertheless, these additives have atendency to react with epoxy resins and are therefore notstorable in these coating systems.
By developing DISPERBYK-2151, BYK has created an
innovative additive that is highly efficient thanks to aminegroups, but also has excellent storage stability in epoxy
systems due to the encapsulation of these groups.
With DISPERBYK-2152, BYK is able to offer a productthat, as a 100 % active substance, contains no volatilecomponents or solvents and is therefore ideal for
AgBB-compliant coatings.
DISPERBYK-2155 and BYK-9076 have proven to beideal for use in self-leveling polyurethane coatings.
DISPERBYK-2155 also has a tin-free variant named
DISPERBYK-2155 TF.
BYK-9076 exhibits very strong viscosity-reducing properties,
which allows it to be used in primers. Due to its highly
amine character, the processing time should always bechecked when used with aliphatic polyurethane systems.
The choice of wetting and dispersing agent is critical forachieving reproducible results during application. The strong
viscosity reduction can facilitate defoaming and improve theleveling properties of floor systems.

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Floor coatings

To achieve this, products are used that give the system
pseudoplastic or thixotropic flow properties.
If a system has thixotropic flow properties, the overall
viscosity is already significantly lowered by low shear forces,
giving the material very good application properties.
The increase of viscosity after application takes place after
a delay. This ensures good leveling of the coating and agood air release.

Storage stability
In floor coatings, it is particularly difficult to avoid thesettling of fillers/pigments. One reason for this is the highamount of high-density fillers. Furthermore, the systems
are subjected to temperature fluctuations and vibrations
during transportation and storage, which can increase settling.
To prevent this, rheology additives can be added to thesystem. However, doing so must not have a negative impact
on parameters such as leveling and defoaming/air release.

Additives that create a pseudoplastic flow behavior are also
suitable for use in floor systems. The use of these products
also brings about a reduction in the viscosity through shear.
The rebuilding of the structure takes place immediately after
the shear stress ceases to be applied. Therefore, a very low
yield point must be ensured for this application. Only thencan sufficient air release and good leveling occur.
To ensure good storage stability combined with good
defoaming and leveling properties, it is important to selecta kind of additive that precisely complements the rest of
the formulation components and additives.

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Floor coatings / Storage stability

Liquid rheology additives
The RHEOBYK-410 range is based on modified ureas, whichhave been dissolved in various carriers. When incorporated
into the coating system, extremely small crystalline particles
are formed. These crystals use hydrogen bonds to form athree-dimensional network structure and create a thixotropic
flow behavior. The additives in this class can be used
independently of the chemical composition and the solids
composition of the system, if the polarity is compatible withthe additive. The formation of this network structure meansthat using additives such as RHEOBYK-7410 ET prevents
pigments from settling. The efficiency is not affected by
the addition of the amine hardener.
RHEOBYK-430 can also be used to prevent the settling ofsolids in highly filled systems. This urea-modified polyamide
generates a pseudoplastic flow behavior that prevents thesettling of solids during storage and after application.

Powder rheology additives
Additives in this class are made up of clay, the surfaces ofwhich have been modified to make them suitable for use insystems with varying polarities. They are delivered in powder
form and can be added to a suitable carrier (e.g. solvent
or reactive diluent), ideally in a pre-mix (also known as a“pre-gel”), in order to exploit their full potential. There arealso “preactivated” types which can be incorporated straightaway. Examples of these additives include products from the
CLAYTONE range. In an idle state and with no shear forces
present, the system builds a three-dimensional network,
which allows the viscosity to increase. This network can be
destroyed by the use of shear forces, leading to a reductionin the viscosity. After the shear forces have subsided, theviscosity is then rebuilt after a delay.

Products from the GARAMITE range can be incorporated
directly in the formulation. Even low additive quantities andlow shear forces during incorporation are enough to achievea very efficient increase in viscosity.
Further positive properties of GARAMITE products include a
low tendency to form dust, as well as the high bulk density.

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Floor coatings

Defoaming/air release
We often hear about “defoamers” in connection withremoving gas bubbles from a liquid coating by using an
additive. The term “air release agent” is also commonly
used. These terms are closely linked to one another, andboth additive classes are necessary in order to remove gas
bubbles from a coating. “Air release” entails the foam

bubbles contained in a liquid film combining to form larger
foam bubbles. In doing so, the ascent rate increases inaccordance with Stokes’ law. “Defoaming” is when the
bubbles have reached the surface, the lamella of the
bubbles is destabilized and the bubble bursts.

Comparing defoaming and air release

Foam at the surface.
Defoamers destabilize the foam bubbles.

Air entrapment in the system.
Air release agents accelerate the ascent of the bubbles to the surface.

G.01

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Floor coatings / Defoaming/air release

In practice, it is not possible to make a precise distinction
between the additive classes of “defoamer” and “air releaseagent” as they tend to carry out both functions to a degree.
Therefore, for simplification purposes, only the term
“defoamer” will be used in the following section.
Foam is one of the greatest challenges in floor systems.
There are many reasons why this is the case. First of all,material viscosities tend to be high, making it difficult for
the foam bubbles to ascend in the film. In addition, a highfiller content introduces air, which adheres to the solid
particles and is only released from these particles later on,
for example due to insufficient dispersal. Moreover, in thecase of solvent-free systems, it is not possible to use solvents
such as xylene to reduce the viscosity and support thedefoaming process. Often, the foam bubbles only reach thesurface when the viscosity has already increased significantly

and the foam bubbles can no longer burst, or after a bubble
has burst it is no longer possible to ensure sufficientleveling. This often means that, for example, self-levelingfloor coatings appear to be free of foam on the day of
application, but then foam marks or pinholes appear a few
days later. Reaction foam in PUR-based or polyaspartic
systems is caused by the reaction of the isocyanate withwater or moisture, and is generally only visible in the formof pinholes once the system has cured.

Example of good andinsufficient defoaming
in a floor formulation

Mechanical air
release with the aidof a spiked roller

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Floor coatings / Defoaming/air release

This is why it is recommended to add the defoamer to themillbase, even if this is being processed under vacuum. It is
often the case that the defoamer quantity is distributed
across different production stages, as otherwise the strong
shear forces will cause it to be too compatible with thesystem and it will lose its efficiency. However, depending on
the compatibility of the defoamer, it is important to ensurethat it is processed for a sufficient incorporation time, as
otherwise undesirable effects, such as cratering, can arise.

Selection criteria for defoamers
Requirement

Defoamer selection

Pigment concentrate or
co-grindMedium-strength defoamer, silicone-free (optional)

Non-pigmented system

Compatible defoamer

PrimerPrimary effect of substrate wetting additives:
the better the wetting, the faster the air displacement/defoaming

Roller coating

Low coating thickness, high air incorporation, therefore medium-strength defoamer in very low
dosage, recommended: Combination with a surface additive, such as BYK-3550 (reduces negativeside effects e.g. cratering)
T. 02

High

General overview to help select a defoamer

BYK-1799*
BYK-1796*

Defoaming properties

BYK-A 535 T
BYK-1790*
Starting point
BYK-1760*

BYK-088

BYK-1794*

Low

BYK-1795*

Low
Polymer/silicone defoamer  

Incompatibility
Polymer defoamer  

Silicone defoamer   * 100 % non-volatile matter or active substance

High
G.02

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Floor coatings

Optimization of the surface
Surface defects affecting the appearance and protectivefunction of the floor coating often emerge during and after
application. Typical surface defects include:• Poor substrate wetting(caused by contaminated concrete)• Cratering• Formation of Bénard cells, flooding/floating• Trowel marks

A fundamental factor in all defects of this kind is thedifferent surface tension of the materials involved and theresulting interfacial tension differences. These differences
can be caused both by processes taking place during curing(cross-linking reaction, settling of the fillers) as well as by
the application process itself (contaminated concrete orapplication equipment, dust, droplets of perspiration).

Figure G.03 illustrates common surface tension differencesthat can occur when using different floor coating systems.

Surface tension differences between different raw materials

mN/mSolvent

Substrate

Liquid top coat

80

Water

50

Moisture-curing polyurethane40

Difunctional reactive diluent
30

Monofunctional reactive diluent
Xylene20

Epoxy/polyurethane, self-leveling

UV-stable epoxy
Epoxy bisphenol-based A/FContaminated concrete

White spirit

0
G.03

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Floor coatings / Optimization of the surface

To avoid surface defects and ensure sufficient wetting,additives are used to influence the surface tension of thecoating system in a targeted manner. Usually these products
are additives based on polysiloxanes (silicone) or
polyacrylates (acrylate additives). If considerable surface
tension differences between the coating system and substrateneed to be balanced out, polysiloxanes are the preferredsolution. They can significantly reduce the surface tension of
the liquid coating system and are therefore used to improve
the substrate wetting, or as an anti-cratering additive.

In floor systems it is best to use polysiloxane-based additives
that have a specific incompatibility with the coating systemand therefore also have a defoaming effect (e.g. BYK-320).
Moreover, silicone additives can optimize the surface of thecured coating film, improve cleanability and make thesurface more resistant to scratching. In this regard, it isimportant to check the impact on the surface slip,
so that no unwanted slip is introduced to the surface.

Additives from the polyacrylate class can also be used.
Polyacrylates are capable of balancing out surface tension
differences. Compared with classic polysiloxanes, however,polyacrylates cause less of a reduction in the surface tension
and also do not increase the surface slip. They are therefore
predominantly used to improve leveling. The BYK-3550
additive is particularly recommended for floor coatings. Even
though it is based on polyacrylate chemistry, it strongly
reduces the surface tension, similar to a polysiloxane-based
additive. In the cured coating film, this additive has barely
any effect on the surface slip, unlike many polysiloxanebased additives.

Optimum combination of defoamer and surface additive

Control

No optimum combination of defoamer
and surface additive, too incompatible

Optimum combination of defoamer and surface additive

G.04

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Floor coatings

Troubleshooting for floor coatings (1/2)

Carbamate formation (amine blushing)

Fish eyes

Settling

At low curing temperatures (below 10 °C),
some hardeners tend to bring about achemical reaction with the carbon dioxide
and the moisture from the air, forming
carbamates, which no longer participate in
the hardening reaction. In this scenario,
a mat, sticky film often develops on thesurface of the floor. This will not provide
good adhesion for the next coating layer. Thissurface defect can sometimes occur in isolated
spots. Large marks often develop, especially inpoorly ventilated or cold zones on the floor. In
such cases, it is important to check thesuitability of the hardener for use in cold
ambient temperatures. There are hardeners
that have a stronger or more reduced
tendency to form carbamates. Silicone-based
surface additives can significantly reduce theformation of carbamates. This takes place
primarily through the formation of aninterface at the surface, which impedes
CO2 diffusion into the coating.

Fish eyes are individually occurring, large,
round surface defects that can also be
circular. Fish eyes are often caused by
defoamers/air release agents that are too
incompatible, or by low shear forces
when incorporating these additives. Morecompatible defoamers/air release agentsor improved incorporation conditions for
defoamers can solve this problem.

High-density fillers and pigments have atendency to form sedimentation in epoxy
systems. Sometimes this phenomenon
occurs only after the low-viscosity hardenerhas been incorporated during processing.
Additives based on modified ureas (e.g.
RHEOBYK-7410 ET) can provide aneffective protection against settling even atvery low concentrations of 0.1–0.3  %.
Special organophilic phyllosilicates such as
GARAMITE-7305 can remedy the problem
without any significant reduction in gloss.

Trowel marks
Trowel marks occur where there are
localized surface tension differences
when processing the system during thecuring stage. These are often only visible
once the surface has cured. They canbe reduced by using products suchas BYK-320 or BYK-3550.

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Floor coatings

Troubleshooting for floor coatings (2/2)

Leveling problems

Reducing the surface slip (anti-slip)

Leveling problems can be caused by aninhomogeneity in the surface tension at theinterface with the air or by pseudoplastic
rheological behavior. In the first case, siliconebased surface additives such as BYK-320 or
BYK-333, as well as polyacrylates such as
BYK-354 or BYK-3560 can help. In thesecond case, a considerable improvement canbe achieved by using viscosity-reducing
wetting and dispersing additives (BYK-9076,
BYK-220 SN, DISPERBYK-111), especially inhighly filled systems. Some rheology additives(e.g. pyrogenic fumed silica, polyamides,
hydrated castor oil derivatives, simple
organophilic phyllosilicates) with a strong
pseudoplastic character can also cause
leveling issues in high dosages. In such cases,
the use of additives based on modified ureas(RHEOBYK-7410 ET) are recommended for
adjusting the rheological properties.

If the surface slip of a floor coating is too high, it
can cause accidents. In such instances, high dosesof silicone additives should be avoided. Standardpractice is usually to sprinkle the surface with silica
sand, carborundum or rubber granulate – however
all these measures produce a highly structured
surface. A homogeneous and not too slippery
surface can be achieved using anti-slip wax
additives such as, for example, CERAFLOUR 970.

Flooding/floating and Bénard cells
Both phenomena are an indication of poor
pigment stabilization. The insufficiently
stabilized pigments can have a tendency toseparate horizontally or vertically. Controlled
flocculating (BYK-P 104 S, BYK-220 SN) or
deflocculating wetting and dispersing additives(DISPERBYK-2152, DISPERBYK-2155/
DISPERBYK-2155 TF, BYK-9076) caneffectively prevent these defects.

02/2024
FL-TI 1

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