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DuPont Zonyl

™

Penetrating Sealers

The Solution for Protecting Porous

Surfaces

The preservation of porous substrates is one of

DuPont’s major preoccupations. DuPont, a world

leader in fluorochemistry has developed a line of

Zonyl

fluorinated additives that provide a durable

and transparent protective barrier against oil and

water stains on stone, unglazed tile, terra cotta, and

other porous masonry and mineral surfaces. When

added to penetrating sealer formulations, Zonyl

fluorinated additives chemically bond to the surface,

providing a transparent vapor-permeable coating

with no effect on the appearance of the surface.

This document discusses problems arising in the

treatment of porous materials, why it is necessary

to treat them against external effects, and some

solutions developed by DuPont.

• not change the permeability to water vapor

• not change the color or texture of the surface,

even after aging

• have an adequate depth of impregnation

Mode of Action of Zonyl

Fluorinated Additives

Concept of Wettability

A surface has a greater tendency to become stained

when a liquid (water, grease, grape juice, etc.) can

easily wet it. This phenomenon is best illustrated

using the

wettability concept.

The wettability of a

surface can be described by the angle of contact

θ,

an angle formed between the tangent to a drop of

liquid drawn at the point of contact between the

liquid and substrate. Three cases can be seen in

Figure 1.

Advantage of Water and Oil Repellent

Products

Definitions

water repellent

is a product intended to limit the

penetration of water into the pores and capillaries of

a surface without altering its mechanical and

aesthetic qualities. Its action is to make the material

hydrophobic, meaning that it does not allow itself to

be penetrated by water.

oil repellent

is used to protect materials from

grease stains (petrol, lubricating oil, edible oil, etc.).

Material that has been made oleophobic does not

allow itself to be penetrated by oils.

A good

water repellent

and

oil repellent

must:

• create a surface that is impermeable to water;

i.e., reduce capillary activity

• create a surface that is impermeable to oil or

grease stains

Figure 1. Different Wetting Situations of a Liquid on a Solid

The wettability of a solid depends largely on the

interactions between the surface of the solid and the

liquid. This occurrence is characterized by the

energy of the material’s surface: the higher this

energy, the more easily the surface will be wetted,

and, therefore, the more susceptible to stains. By

defining g

, the surface tension of the liquid, and

the energy of the material’s surface, one can then

demonstrate that a liquid can only fully wet a solid

≤γ

Therefore, by trying to reduce

, the number of

liquids likely to wet the surface is limited. Conse-

quently, chemists have developed novel products in

order to modify this parameter.

Wetting of Porous Surfaces

A wall can be considered as a collection of capillar-

ies that are more or less horizontal. Liquid can

penetrate by capillary action into such porous

materials and migrate inward. This capillary rise

(penetration) is determined by the generalized

JURIN equation:

∆P

= (2γ

cosθ)/r

where:

∆P

= capillary pressure

r = capillary radius

= surface tension of liquid

To prevent water from penetrating into the material,

it is, therefore, necessary to increase the angle of

contact beyond 90° (where cosθ is negative), so as

to have a negative capillary pressure in order to

repel the water out of the capillary (Figure

2).

obtain a high angle of contact, and, therefore, a low

surface energy, DuPont has developed a series of

Zonyl

fluorinated additives, which are among the

most effective products on the market. This effec-

tiveness is explained by the special characteristics of

the fluorine atom, which are discussed in the next

section.

Among the most remarkable structural properties of

carbon-fluorine bonds we should mention is the

very high electronegativity

of fluorine together

with its

small ionic radius,

leading to a very stable

C-F bond with very low polarizability.

Table 1

Characteristics of the Carbon-Fluorine Bond

C-F Bond

High binding energy

High rotating energy

Low intermolecular bonds

Great thermal and

chemical stability

Rigid molecule

Low surface energy:

water and oil repellency

A model surface completely covered with –CF

groups possesses an extremely low surface energy

of approximately 6 mN/m. In order for a liquid to be

able to fully wet such a surface, it must have a

surface tension of less than 6 mN/m; however, such

a liquid does not exist (Table

2).

Table 2

Surface Energy of Common Materials

(in order of decreasing surface)

Substrate

Water (distilled)

Organic coatings

Waxes, paraffins

Dirt and oil

Polytetrafluoroethylene (PTFE)

Zonyl

fluorinated additives

Surface tension (mN/m)

35–40

20–25

15–20

Figure 2.

Capillary Pressure Depending on the Angle of

Contact

Advantages of the Fluorine Atom

The water repellent and oil repellent action of

fluorinated additives resides in

reducing the

surface energy

of the treated material. This prop-

erty is provided by the fluorine atom, which has

very little interaction with other chemical elements.

It, therefore, gives a very low surface energy to the

surface on which it is applied.

By grafting perfluorinated links onto acrylic skel-

etons, DuPont has succeeded in developing Zonyl

fluorinated additives, the chemical structure of

which makes it possible to build a fluorinated

barrier that stays very well organized at the surface-

air interface with a particularly low surface energy

for commercial products.

Hence, a surface treated with a Zonyl

fluorinated

additive is not easily wetted by most aqueous or

organic liquids (γ

water

= 72 mN/m,

olive oil

32 mN/m,

petrol

= 24 mN/m), because the surface

energy of the substrate is a great deal less than

20 mN/m. This type of treatment, therefore, consti-

tutes a very effective protection against water and

grease stains (Figure

3).

Figure 3. Oil Resistance of an Untreated and Treated Material

with a Flourinated Additive

the material with an extremely low-thickness coating

that provides excellent water and oil repellency. It

thus creates “negative” capillary forces that prevent

water from penetrating into the material. Because the

pores are not obstructed, the substrate retains almost

all of its porosity, while permeability to water vapor,

and, as a result, the material’s behavior during

drying are scarcely affected. This system of protec-

tion, therefore, complies with one of the basic rules

for the protection of dwellings specifying that the

water vapor produced inside a house must be able to

escape freely.

Figure 4

summarizes the differences between a

Zonyl

water and oil repellent treatment and a

waterproof coating.

Permeability to Water Vapor

While impermeability to liquid water is a goal for a

fluorinated coating, one also requires a permeability

to water

vapor

equivalent to that of the untreated

material. It is, in fact, necessary to make significant

modifications to the hydrothermal exchanges

between the inside and outside of the material or

else see the deterioration of the protective film

(blistering, efflorescence, spalling, and exfoliation).

On a stone with fine pores, the application of a

watertight film causes deterioration as a result of

reduced evaporation: the internal part of a porous

element is susceptible to retaining water that may

come from periodic penetrations. Such water tends

to move around inside the capillary network.

Anything that prevents water from escaping (water-

tight film) creates an increase in hydraulic pressure,

internally pushed from the inside to the outside,

causing damage by exfoliation of the stone. Such

damage is even more significant where the surface

of the stone is treated with a film-forming agent that

has strong concentrations of active matter.

Laboratory measurements have made it possible to

estimate the permeability of materials treated with

different additives (Table

3).

Research shows that

Zonyl

fluorinated additives do not alter the

material’s permeability to water vapor.

The results show that a Zonyl

fluorinated additive

does not impair the material’s permeability to water

vapor. In fact, it modifies the walls of the pores in

Table 3

Permeability Measurements

Product

Applied

Loss of permeability

Conventional

Silicone

Zonyl

Acrylic Additive, Additive, Fluorinated

Additives, %

40–60

5–20

2–6

Figure 4. Diagram Showing Water Balance in a Wall

Depending on the Protection Used

Untreated wall

Wall treated with a

Zonyl

fluorinated additive

Wall treated with an

impervious coating

Rising damp

Properties of Zonyl

fluorinated additives

The main properties provided by Zonyl

fluorinated

additives that are associated with the characteristics

of the fluorine atom and the C-F bond are summa-

rized in section “Advantages of the Fluorine Atom.”

• Resistance to water

• Resistance to oil, grease, dirt

• Easy to clean

• Permeability to water vapor and gases

• Translucent coating; no unpleasant optical effect

The development of Zonyl

fluorinated additives

benefits treatments, which consist of preventing the

migration of water and grease stains into porous

materials.

Not only do Zonyl

fluorinated addi-

tives protect porous substrates from water and

stains, but they also allow water vapor to evapo-

rate from internal areas.

In the series of products offered by DuPont, there is

at least one that will help you solve your problem.

Zonyl

Fluorinated Additives

DuPont has a line of Zonyl

fluorinated additives

intended for the protection of stone, unglazed tile,

grout, and other porous masonry and mineral

surfaces. It is comprised of products in aqueous or

organic solutions.

Table 4

lists information relating

to the characteristics and uses of the different

product offerings.

You will find additional information concerning the

formulation and application of these products in

individual technical datasheets corresponding to

each product, which can be accessed at our website,

www.dupont.com/zonyl. To request samples or

technical assistance, please call 1 (866) 828-7009,

and, to purchase a product, call 1 (800) 441-9140 or

1 (800) 441-9139.

Table 4

Characteristics of the Different Zonyl

Fluorinated Additives for Porous Surfaces

Penetrating

Sealer

Zonyl

225

Zonyl

329

Zonyl

8740

Appearance

Translucent liquid

Milky amber

colored liquid

Light amber

colored liquid

Solvent

Butyl acetate

Active Matter, %

—

Flash Point,

°C

(°F)

26 (79)

Performance Attributes

Low porosity surfaces.

Stain resistance and

repellency

High traffic areas.

Not available in the U.S.

Repellency and

stain resistance

Water

4–4.5

4.5–5.0

—

U.S. Sales and Services

For placing orders, please use our convenient 24 hr, toll free number,

1-800-441-9140.

For additional literature

or a product sample, call

1-866-828-7009.

If you prefer, you can write to us when you visit our website,

www.dupont.com/zonyl.

DuPont Chemical Solutions Enterprise

Customer Service Center

Barley Mill Plaza, Bldg. 23

Wilmington, DE 19898

The information set forth herein is furnished free of charge and is based on technical data that DuPont believes to be reliable. It is intended for use by persons

having technical skill and at their own discretion and risk. DuPont makes no warranties, expressed or implied, and assumes no liability in connection with

any use of this information. Nothing herein is to be taken as a license to operate under or a recommendation to infringe any patents.

The DuPont oval logo, DuPont

™

, The miracles of science

, and Zonyl

are trademarks or registered trademarks of DuPont.

(4/03) W-400228 Printed in U.S.A.

Reorder No.: K-00507

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