New uses of fluorine-containing surfactants are used in water-based wood coatings

Wood surface coatings are mainly used for protection and decoration purposes. In recent years, wood coating manufacturers have invested their research and development resources in improving the performance of water-based coatings due to
environmental
. Water-based paint paint has outstanding environmental advantages, such as volatile organic compounds
VOC
content in accordance with regulations, lower odor and less harmful organic gases, lower flammability, reduced allergies and skin irritation to make the working environment safer and healthier, reduce fire hazards. At the same time, there are economic advantages, such as lower insurance premiums, lower storage costs and lower costs for disposing of hazardous waste. There are also construction advantages, such as the use of existing equipment for the construction of different thickness coatings, reducing the labor required for cleaning.
, however, changes from solvent-based coatings to water-based coatings have made it necessary to develop coating systems that contain more parts and are more complex. The surface stress of water (
72
/
cm
) is much higher than that of solvents. Simply reducing
VOC
without using the right combination of surfactants will lead to many surface defects such as shrink holes and orange peel formation, so the wetting, leveling, foam control and surface rejection of water-based wood coatings are becoming increasingly challenging for formulators. An effective solution is to add appropriate additives to improve performance. Surfactants in wood coatings provide two main functions: ensuring smooth construction of wet films and increasing the adhesion of lacquer films to substrates;
previous studies, we have demonstrated that fluorine-containing surfactants can be used as multi-functional additives for
VOC
in latex paint for construction to provide wetting, leveling, adhesion, oil rejection and stain resistance
2
. In this paper, we discuss the role of fluorine-containing surfactants in water-based wood coatings and how they, as cost-effective additives, can help reduce surface pressure and improve wetting, leveling, oil rejection and the performance of chemically resistant media during film construction.
almost all types of resins such as acrylic, epoxy, aolate and polyurethane resins can be used to meet the specific needs of water-based formulations
3
. For water-based wood coatings, the main coating systems include single-component acrylic emulsions or dispersants, single-component polyurethane dispersions (
PUD
) or
PUD
acrylic blending systems, single-component aleate resins, and two-component water-based polyurethanes (polyols and isocyanates). Acrylic substates are usually a variety of monomer emulsions in the water to form a stable gel-like solid particles (latex), acrylic dispersion film formation including water evaporation, polymeration, and finally through the polymer particles diffused between each other to form a coating film
4
. Water-diluted polyurethane dispersions (
PUDs
) and polyurethane
-
acrylic mixing systems provide approximate polyurethane-like performance and are easy to construct as single-group coatings. In this chemical process, the modified isocyanate molecule is stable in water and reacts with polyols to produce a water-based polyurethane dispersion
3
.
this study used water-based self-cross-linked acrylic dispersions as a base material because air-dried water-based acrylic dispersion coatings are widely used in wood decoration, which requires fast, low-temperature curing. The coating is hard and dry very quickly
5
. Importantly, the use of fluorine-containing surfactants does not cause heavy coating problems in wood coatings, as our data confirm.
Experiment
Coating Formulation and Application
In our experiment, the base material used was a medium hardness, self-crossed acrylic dispersion with a minimum film-forming temperature (
MFFT
) of
113oF
. Five formulations


A
,
B
,
C
,
D
and
E)
were studied to evaluate the performance of various surfactants. Table
1
general overview of the composition of these five formulations.
the solid content of the formula
33%-34%
and viscosity of
8,000-8,500 cps
. The coating (diluted with
5
% water) is sprayed three times on the oak substrate using conventional air atomization spraying, and the air pressure is
40-50
pounds
/
square inches (
psi
)
,

45
minutes each. Each dry film is
55-60
microns.
surface
use
KRUS
to measure surface stress using a flat plate method. Reduce the sheet to the liquid surface and measure the downward force applied to the sheet to calculate surface stress.
Oil Repulsion
uses a angler to determine the contact angle of water and oil on a coated wood substrate equipped with a camera from the high-speed charge coupling device
(CCD)
for image capture. Use a syringe to drop water or hexane to the surface. A computer-assisted angler measures the contact angle of a droplet, assuming that the droplet is stable and geometric after
1
minutes. The high contact angle value of the oil indicates that the coating has good oil-
properties,
lower value indicates that the oil can wet the surface.
chemical media resistance
tested against
KCMA A161.1
U.S. national standard. Before testing, allow the coating to dry in the air for
7
days. Place each test material at
3
ml (vinegar, orange juice, ketchup, coffee, olive oil and alcohol at a concentration of
50%
) on the surface of the paint film for
24
hours. Then clean the surface with clean water and dry it with a clean cloth. The results are assessed by observing any changes in the paint film, such as color, gloss, and coating damage.
three
are applied to the board, each with a dry film thickness of
55-60
microns. After drying in the air at room temperature for
24
hours, place eight models as follows: model
1
,
2
face-to-face, model
2
,
3
opposite back, model
3
,
4
opposite back, sample Board
4
,
5
back-to-back, model
5
,
6
face-to-face, model
6
,
7
opposite, model
7
,
8
opposite back. Peel the model and rate the viscosity level.
re-coating
re-coating is evaluated with adhesion tests (
ASTM D-3359
scratch tape tests
)
. Before the test,
paint
dry in the air for
7
days.
results and discussion
foaming
surfactants are diluted with water, the same amount of addition in the coating formulation, by shaking the paint by hand to produce foam. Figure
1
the volume of the foam
15
15 seconds after shaking. The graph shows that the amount of foam produced by four fluorine-containing surfactants is lower than that produced by silicone surfactants.
Zonyl
®
FS-610
,
Capstone
®
FS-61
and
Capstone
®
FS-63
fluorine-containing surfactants are specially produced low-foam products that produce virtually no foam after shaking.
Reduces Surface Stress
The surface pressure of fluorine-containing surfactants in deionized water and commercialized wood coating substrates is shown in Table
2
, and water-diluted polyurethane dispersions (
PUD
) are also widely used in single-group wood coating systems due to their proximity to polyurethane. The reduction of surface stress is listed and compared with the acrylic resin studied. Compared to silicone surfactants, fluorine-containing surfactants are most effective in reducing surface stress in water and water-based substrates, especially polyurethane dispersion (
PUD
) resins. Of the four fluorine-containing surfactants, the next generation of
Capstone
®
surfactants has better surface stress reduction than
Zonyl
®
products.
moisturizing and leveling
coating is sprayed on the oak board, and the surface appearance of the different formulations is
2
shown. Optical microscope photographs (
8
magnification) formulated using fluorine-containing surfactants and silicone surfactants are shown in figure
3
. Using
Capstone
®
FS-61
and
Capstone
®
FS-63
formulations with a small amount of desiccant can achieve good wetting and leveling performance. Serious surface defects such as shrink holes and orange peels were observed using the
Zonyl
®
FSP
formulation with bubbles on the surface, and the formula using silicone surfactants was observed. This

Zonyl
®
FS-610
,
Capstone
®
FS-61
and
Capstone
®
FS-63
fluorine-containing surfactants help improve the wetting and leveling of water-based wood coatings.
is the behavior of liquid coating expansion on the surface, successful coating of the coating is necessary. Wetting performance can be improved in two ways:
1
) improves the surface energy of the substrate by cleaning, removing contaminants and pre-treatment of the substrate

; Fluorine-containing surfactants are more effective at reducing surface stress than silicone surfactants, resulting in better wetting properties.
is the ability to achieve a smooth, uniform surface. This is a much-needed quality for high-gloss wood coatings and hood paints. During the formation of the coating film, many problems may occur, such as insufficient wetting of the substrate, poor mobility, the formation of shrink holes and floating colors. These problems affect leveling performance. In general, the leveling properties of coatings are controlled by surface stress, fluidity, film thickness, solvent volatility rate and pigment dispersion. In our tests, the thickness of the thickener, dry film thickness and cosolent used were the same, with the difference being the surface strength of the coating. Therefore, it can be reasonable to think that: compared with silicone surfactants, fluorine-containing surfactants can reduce surface pressure, so leveling is better. Fluorine-containing surfactants promote the wetting of substrates to prevent shrinkage, uneven coating of fisheyes and surfaces, and the elimination of these surface defects is helpful for achieving good leveling. Fluorine-containing surfactants, due to their rapid migration and good compatibleness, can achieve the same surface stress throughout the surface area, which also contributes to leveling. Overall, the use of fluorine-containing surfactants in water-based wood coatings helps to achieve good gloss and even reflection properties and to form smooth coatings.
oil repulsion
the contact angles of water and oil on different paint films are listed in Table
3
, figures
4
and
5
show the contact angles of different formulations of water and oil. The contact angle of the formula water using the silicone surfactant is slightly higher than that of the formula using fluorine-containing surfactants. However, the oil contact angle formulated using silicone surfactants is very small (close to zero), which means that oil stains or petrochemicals can almost completely spread on the coating surface. The oil contact angle on the fluorine-containing surfactant formula is much higher than that of the silicone surfactant, which is oiled into beads on the surface. This shows that the addition of fluorine-containing surfactants can provide excellent oil repellent for lacquer film.
viscosity
test results are shown in
4
4. Add a fluorine-containing surfactant
Capst