Fabrication of superhydrophobic wood surface

1. Fabrication of superhydrophobic wood surface with enhanced
environmental adaptability through a solution-immersion process
Peng Cai b
, Ningning Bai a
, Lan Xu a
, Cui Tan a
, Qing Li a,
⁎
a
School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, PR China
b
Faculty of Materials and Energy, Southwest University, Chongqing 400715, PR China
a b s t r a c t
a r t i c l e i n f o
Article history:
Received 29 January 2015
Revised 2 July 2015
Accepted in revised form 24 July 2015
Available online 30 July 2015
Keywords:
Wood
Superhydrophobicity
Stability
Environmental adaptability
Oil/water separation
A simple solution-immersion method for fabrication superhydrophobic wood surface is reported in this paper.
For a deeper discussion of the effect of adhesion mechanism on the stability of superhydrophobic surface, lauryl
aldehyde and lauric acid were chosen to modify wood surface. Two kinds of superhydrophobic wood with con-
tact angles of 160° (SW1) and 154° (SW2) were successfully fabricated through a simple solution-immersion
method. In comparison to SW2, the SW1 which was obtained by chemical bond possesses not only better
superhydrophobicity but also more extraordinary stability when exposed to aggressive medium including acidic
and basic corrosive solutions, organic solvent, and simulated seawater. Additionally, SW1 shows an excellent
self-cleaning ability. This method is expected to prolong the lifetime of the woodwork under our living environ-
ment. Meanwhile, this method can also apply to cotton textile and filter paper for oil/water separation. Such re-
search could not only help us to further understand the effect of the adhesion mechanism on the surface stability,
but also give us the design principle for the fabrication of a superhydrophobic surface with great strength.
© 2015 Elsevier B.V. All rights reserved.
1. Introduction
From ancient times to the present, wood is widely used in the fields
of furniture, traffic, and construction for their special properties such as
high strength-to-weight ratio, eco-friendly, and renewability. However,
because of its special porous structure and large number of hydroxyl
groups on the surface [1], wood is easy to absorb water and vapor at am-
bient condition, which would lead to the cracking, mildew, rot, degrada-
tion of wood materials and strongly affects the durability of wooden
products. The occurrence of atmospheric corrosion needs a hydrophobic
film that covers the wood surface. In recent years, superhydrophobic
surfaces have aroused enormous interest and been investigated by
many researchers for their special functions, such as self-cleaning
[2–7], antipollution [8,9], anticorrosion [10–12], and oil/water separa-
tion [13–16]. Meanwhile, wood materials could be applied in more
fields and their service life would be prolonged with the properties of
superhydrophobic coatings.
For the past few years, there are some researches about the fabrica-
tion of superhydrophobic coatings on wood substrate were reported.
Hsieh et al. [17] have fabricated the fluoro-containing silica coating on
wood substrates, which showed good repellence to water and sunflower
oil. Wang et al. [18] have fabricated superhydrophobic wood surface via a
sol–gel process followed by a fluorination treatment of 1H, 1H, 2H, 2H-
perfluoroalkyltriethoxysilanes (POTS) reagent, and with the combination
of high surface roughness of silica nanoparticles and the low surface free
energy film of POTS, the wood surface has turned its wetting property
from hydrophilic into superhydrophobic. Wang et al. [19] have fabricated
superhydrophobic coating on a wood surface through a wet chemical
process. Liu et al. [20] have fabricated superhydrophobic wood surface
from potassium methyl siliconate through a convenient solution-
immersion method. Most of the reports just analyzed the composition
of superhydrophobic wood surface and did not do stability test. As we
all know, most superhydrophobic materials have poor durability [21],
when exposed to a living environment, their micron/submicron binary
structures and low surface energy layers could be easily and permanently
degraded by organic solvent, seawater, acid rain, etc. Hence, facile prep-
aration method using cheap and non-fluoride materials to fabricate
good stability superhydrophobic film on wood substrate is still a major
challenge. However, so far most studies have focused on the formation
of superhydrophobic coating on wood surface, and research about the ef-
fect of adhesion mechanism between coating and low surface energy on
the stability is extremely rare. In fact, research relating to the adhesion
mechanism of coating and low surface energy, especially adhesion
mechanism that influence the stability of superhydrophobic surface, is
particularly important. Such research could not only help us to further
understand the effect of the adhesion mechanism on the surface stability,
but also give us the design principle for the fabrication of a
superhydrophobic surface with great strength.
Hence, in order to find the effect of adhesion mechanism on the sta-
bility of superhydrophobic surface, two different low surface energy
Surface & Coatings Technology 277 (2015) 262–269
⁎ Corresponding author.
E-mail address: liqingswu@163.com (Q. Li).
http://dx.doi.org/10.1016/j.surfcoat.2015.07.060
0257-8972/© 2015 Elsevier B.V. All rights reserved.
Contents lists available at ScienceDirect
Surface & Coatings Technology
journal homepage: www.elsevier.com/locate/surfcoat

2. materials were chosen for the modification of wood surface. In detail, a
silane hierarchical structure on wood surface was created firstly by a so-
lution immersion process. Then modification with lauric acid and lauric
aldehyde respectively to lower the surface energy, that is, a comparison
of adhesion mechanism was established. The concrete design is shown
in Scheme 1. It can be seen that the superhydrophobic wood 1 (SW1)
can fabricated by γ-aminopropyltriethoxysilane (APTES) and lauryl alde-
hyde, which can be easily connected by chemical bond, APTES not only
played the role of micro–nano-structures, but also played a role in the
connection of low-energy materials and wood surface. So the optimized
condition for roughness structure has been investigated. For comparison,
APTES and lauric acid were used to fabricate superhydrophobic wood 2
(SW2) under the same condition, and then the stability of two kinds of
superhydrophobic wood was compared from the aspects of acid–base
resistance property, organic solvent repellence, and simulated seawater
immersion test. Additionally, the environmental adaptability of SW1
was evaluated by various tests, including acid rain wash test, water resis-
tance test, and self-cleaning test. Meanwhile, as a research on method,
this design was also applied to cotton textile and other fabrics in our
work. This study could not only expand the application fields and in-
crease the service life of wood materials, but also give us a new slight
of fabricating superhydrophobic surface with great strength.
2. Experimental
2.1. Materials
Ash wood was obtained from Harbin, the dimensions of samples
were 20 mm × 10 mm × 5 mm. All the solvents and chemicals except
γ-aminopropyltriethoxysilane (CR, Shanghai Chemical Reagent Co.),
lauryl aldehyde (CR, Shanghai Chemical Reagent Co.) and lauric acid
(CR, Shanghai Chemical Reagent Co.) were purchased from Chengdu
Kelong Chemical Reagent Co., China. The deionized water used was
Milli-Q water (Milli-Q, USA).
2.2. Pretreatment of ash wood
All 6 sides of wood substrate was polished with SiC paper of succes-
sively finer grit down to 400 grit, rinsed with deionized water, ultrason-
ically degreased in acetone and dried in air.
2.3. Fabrication of APTES film on wood surface
The APTES coatings were prepared on wood surface by a solution-
immersion process. The first step of the fabrication superhydrophobic
wood involved the assembly of an APTES coating on the wood surface.
Typically, the aqueous solution consisted of 2 ml APTES dissolved in
80 ml deionized water in a Teflon beaker. The wood sample was im-
mersed into this aqueous solution, and the mixture was electromagnet-
ically stirred at 60 °C for 5 h. Then by rinsing with deionized water three
times, the APTES coating on wood surface was obtained after first
silanation (condition A). The above experiment was repeated. The
two-layer APTES coatings were obtained after second silanation (condi-
tion B). Finally, the above experiment was repeated for three times, and
the three-layer APTES coatings were obtained after third silanation
(condition C).
2.4. Modification
The surface modification of two-layer APTES coatings on wood sam-
ples was divided into two groups. The sample of one group was im-
mersed into an ethanolic lauryl aldehyde solution (0.01 M) at 60 °C
for 2 h, the SW1 was obtained. Another group was immersed into an
ethanolic lauric acid solution (0.01 M) at 60 °C for 2 h, the SW2 was ob-
tained. Finally, the sample rinsed with ethanol three times, then dried in
a vacuum oven at 120 °C for 30 min. In addition, the method SW1 was
adopted to fabricate superhydrophobic cotton textiles and filter paper
for oil/water separation.
2.5. Characterization and tests
SEM images were obtained on a scanning electron microscope
(SEM; HITACHI S-4800). Surface chemical characterizations were car-
ried out by X-ray photoelectron spectroscopy (XPS; Thermo ESCALAB
250). The water contact angle (CA) and sliding angle (SA) were mea-
sured with a water drop volume of 5 μL using an optical contact angle
meter (POWEREACH JC2000C1) at ambient temperature. The advancing
angle (θA) and receding angle (θR) were measured according to the pre-
vious report [22,23]. The values reported are averages of five measure-
ments made on different positions of the sample surface. H2SO4 and
NaOH were used to adjust the pH value of water in the test.
The stability of two kinds of superhydrophobic wood was evaluated
by various immersion tests, including aqueous solution of different pHs
Scheme 1. Blueprint of fabrication of superhydrophobic wood.
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3. (pH = 2, 5, 7, 9, 12), organic solvent (acetone, toluene, chloroform,
DMF, n-heptane), simulated seawater (3.5 wt.% NaCl solution), and
the transverse section of wood was sealed by epoxy resin (EP).
The environmental adaptability of SW1 was evaluated by simulated
acid rain wash test, self-cleaning test, water resistance test, and the
situation of common household liquids drip on SW1. The chemical
composition of simulated acid rain was shown in Table 1. The water
absorption test was investigated according to Chinese National
Standard GB/T17657-1999 [24]. The dimensions of test samples were
20 mm × 20 mm × 20 mm and immersion into water under 50 mm
and the transverse section of wood was sealed by EP, water tempera-
ture was maintained at 20 ± 2 °C. The self-cleaning performance of
SW1 was demonstrated with white anatase and black graphite as
model contaminant. The household liquids including coffee, wine,
milk, tea, and ink were used to examine surface repellency toward
these liquids on the SW1.
3. Results and discussion
3.1. Fabrication of superhydrophobic surface
3.1.1. Construction of hierarchical micro-nano structure
The surface would present three conditions for preparing a
superhydrophobic wood after silanation. In condition A, the roughness
of APTES layer is undersized for first silanation, although the superhydro-
phobic wood will be prepared after modification by lauryl aldehyde,
but its superhydrophobicity is not the best, the water contact angle is
156°. In condition B, the surface contains a micro–nano-hierarchical
structure after second silanation, these structures are beneficial for the
superhydrophobicity, and the water contact angle reach to 160°. In con-
dition C, the roughness of APTES layer is oversized after third silanation,
and that are adverse for preparing a superhydrophobic surface, and the
water contact angle decrease to 145°. Thus the APTES coatings prepared
by second silanation have been investigated. The surface morphologies
of the wood samples were observed by SEM. Fig. 1 shows typical mor-
phologies of the pure wood and the modified wood. The native wood
shown in Fig. 1a exhibited a microscale cell structure with a typically
smooth surface. The first, second and third silanation woods were
shown in Fig. 1b, c and d. A thin layer of rough nanoscale protuberances
uniformly covered the wood surface, and the roughness of third
silanation wood is larger than the first and second silanation woods.
Both the oversized roughness and undersized roughness would lead to
a smaller contact angle. Careful inspection of the surface indicated that
the surface of SW1 (Fig. 1e) contains a micro–nano-hierarchical struc-
ture. Furthermore, the CA change could be theoretically explained by
the Cassie–Baxter equation [25]
cos θ ¼ f s1 1 þ cos θO
ð Þ−1 ð1Þ
where θ and θo are the water CAs on a rough surface and on a flat surface,
respectively; ƒsl is the fraction of water contact with the surface, and
(1 − ƒsl) is the fractional areas of air/water. The value of θo of smooth sur-
face is constant. Therefore, the larger or smaller surface roughness would
increase ƒsl and lead to the decrease in water CA (θ). But for the
superhydrophobic surface, the trapped air can reduce the ƒsl, and lead
to the increase of CA and decrease of SA. Thus the water drops cannot
penetrate into the grooves, while oppositely is suspended on the
micro/nanostructured surface. The drops can hardly stick on the surface
and will roll quite easily from the surface with a slight inclination, even a
slight vibration.
The surface chemical composition of wood samples before and after
modification was investigated by X-ray photoelectron spectroscopy
(XPS). In the XPS spectrum of the SW1 and SW2 (as shown in Fig. 2a),
the appearance of two typical peaks with binding energies of 150 and
100 eV, corresponding to Si 2s and Si 2p, respectively, indicated the
presence of silicon at the surface, and the ratios of C/O/Si/N are 59.0/
25.0/10.2/5.8 (SW1) and 48.5/31.8/12.0/7.7 (SW2). In addition, the
high-resolution C 1s peak exhibited three distinct sub-peaks at
284.5 eV of C–C bonds, 287.5 eV of C_N bonds, and 288.9 eV of C_O
bonds (Fig. 2b), indicating that the lauryl aldehyde and lauric acid are
successfully grafting on wood surface. The coating of surface with cova-
lently attached silanes is well known [26,27]. This field of search is pre-
dominated by silicone chemistry and could benefit from the ability to
generate nanostructures through the hydrophobization of surface [28].
In our study, the APTES not only played the role of micro/nano struc-
tures, but also played a role in the connection of low-energy materials
and wood surface. The –Si–OH groups of the hydrolyzed silane were ini-
tially assembled on the wood surface via hydrogen bonds with cellulose
–OH groups [29]. As the reaction proceeded, water lost and a covalent
bond was formed. The reaction of the hydrolyzed silanes with the sur-
face –OH groups ultimately resulted in the condensation of a siloxane
polymer. It is well known that the –NH2 can be easily reacted with –
CHO and form –C_N–, which is a classic synthesis mechanism of Schiff
bases, so the high-resolution C 1s peak exhibited sub-peaks at 287.5 eV
(Fig. 2b). Therefore the adhesion mechanism between lauryl aldehyde
and wood surface is chemical bond. However, the carboxyl can hardly
react with primary amine, so the adhesion mechanism between lauric
acid and wood surface is physical adsorption. In addition, two kinds of
superhydrophobic wood were immersed in ethanol for 24 h. We
found that the SW1 still has a good superhydrophobicity, but the SW2
lost superhydrophobicity. This further confirms the adhesion mecha-
nism between low-energy materials and wood surface.
3.1.2. Wetting behaviors
The wetting behaviors of the resulting surfaces were analyzed by
water contact angle (WCA) and contact angle hysteresis (WSA) [30].
As is shown in Fig. 3a and b, the static WCA of SW1 and SW2 was
160 ± 1.5° and 154 ± 2°, and the WSA of SW1 and SW2 was 1 ± 0.5°
and 3 ± 0.7°, respectively. The result shows that two modified wood
surfaces possess superhydrophobicity. The as-prepared surface pos-
sesses superhydrophobicity not only for pure water, but also for corro-
sive liquids, such as acid and alkali. Fig. 3c displays the CA of the
resulting superhydrophobic surface at the different pH values. It can
be clearly observed that SW1 always meets the standard of
superhydrophobicity in the pH range from 1 to 14. However, the CA
values of SW2 preserve larger than 150° only in the pH range from 6
to 7, the CA decreased to 105° and 65° for acidic and basic solution
(pH = 1, 14), especially. The lauric acid is unstable when immersed in
corrosive medium, especially in acidic and basic solutions. Once the air
film became discrete, the droplets with different pH values can pene-
trate the grooves, leading to the decrease of CAs. This observation indi-
cates that the SW1 possesses not only a better hydrophobicity but also a
more extraordinary stability for corrosive liquids such as acidic and
basic solutions.
3.2. The stability of SW1 and SW2
In order to investigate the effect of adhesion mechanism between
low-energy materials and wood surface on the stability of superhydro-
phobic wood, the stability of SW1 and SW2 is compared by the follow-
ing immersion test.
3.2.1. pH stability
The pH stability of SW1 and SW2 was evaluated by measuring the
change in WCA values after treating in the obtained materials with
aqueous solutions of varying pHs. In Fig. 4a, it was found that the SW1
Table 1
The chemical composition of simulated acid rain.
Materials H2SO4 HNO3 Na2SO4 NaNO3 NaCl (NH4)2SO4
Concentration (mg/dm3
) 32 15 12.8 8.4 33.6 18.4
264 P. Cai et al. / Surface & Coatings Technology 277 (2015) 262–269

4. displayed a satisfactory durability with WCA values lager than 150° after
immersion with solution pH = 2, 5, 7, 9, 12, for 95 h, respectively. How-
ever, with the extension of immersion time, the WCA value will de-
crease after treatment with basic solution. For comparison, the SW2
was immersed in solution with varying pHs under the same condition.
In Fig. 4b, the SW2 displayed a satisfactory durability after treatment
with acidic solution, but WCA value will decrease below 150° after
treatment with basic solution, especially the WCA value almost de-
crease to 0° after treatment with strong basic solution only for 30 h,
this could be due to the low-energy material of SW2 that was destroyed
by basic solution, leading to the lose of SW2's superhydrophobicity.
Thus the SW1 is more stable than SW2 after treatment with aqueous so-
lutions of varying pHs.
3.2.2. Immersion test of various organic solvent
The superhydrophobicity of SW1 can be sustained in many common
organic solvents, like acetone, toluene, chloroform, DMF, and n-heptane.
As shown in Fig. 5a, there is no apparent fluctuation of CAs in the value
of CA after treatment with various organic solvents for 100 h. However,
the SW2 possesses superhydrophobicity only treatment with n-
heptane, as shown in Fig. 5b, one can clearly find that the CA value
decreases to 0° after treatment with acetone, chloroform and DMF. This
could be due to the low-energy material of SW2 that is soluble in these or-
ganic solvents, leading to the lose of SW2's superhydrophobicity. There-
fore, the SW1 is more stability than SW2 after treatment with various
organic solvents.
3.2.3. Immersion test of simulated seawater
Considering the harsh environments of industry, it is necessary to
investigate the stability of superhydrophobic wood in simulated seawa-
ter. The SW1 displayed a satisfactory durability with CA values larger
than 150° after treatment in simulate seawater for 120 h. However,
the superhydrophobic coating of SW2 was degraded by simulated sea-
water, and the CA value almost decreased to 0° after treatment with
simulated seawater only for 40 h, this could be ascribed to the
unstability of lauric acid when immersed in simulated seawater, thus
the low surface energy materials of SW2 was destroyed, leading to the
lost of SW2's superhydrophobicity. Therefore, the SW1 is more stability
than SW2 after immersion in simulated seawater.
After these immersion tests, it was found that the SW1 displayed an
extraordinary stability after treatment with aqueous solutions of vary-
ing pHs, various organic solvents and simulated seawater. On the
Fig. 1. SEM images of (a) native wood, (b) first silanation wood, (c) second silanation wood, (d) third silanation wood, and (e) SW1. (f) Photograph of common liquid on the SW1.
Fig. 2. (a) XPS spectra of surface of the pure wood, SW2 and SW1. (b) Corresponding high-resolution XPS spectra of C1s.
265
P. Cai et al. / Surface & Coatings Technology 277 (2015) 262–269

5. contrary, the SW2 has poor stability, and its low surface energy layers
could be easily degraded by these solutions. This further illustrates the
adhesion mechanism between lauryl aldehyde and wood surface is
chemical bond, while adhesion mechanism between lauric acid and
wood surface is physical adsorption, resulting in the SW1 is more stable
than SW2. Therefore, the main target in our following experiment is the
investigation of SW1's stability.
3.3. The environmental adaptability of SW1
3.3.1. Simulated acid rain wash
Industrial and urban developments have worsened worldwide acid
rain problems, which attract a great deal of attention from environmen-
talists and researchers all over the world. Thus, it is necessary to test the
adaptability of SW1 to acid rain, and the adaptability of SW1 was eval-
uated by measuring the change in CA values after scour with simulated
acid rain (SAR). The chemical composition of simulated acid rain was
shown in Table 1, and the pH of simulated acid rain is about 3.5. The di-
ameter of every drop is about 6 mm, and sliding angle is 30°. Two
variables have been investigated. The drop height keep at 20 mm
(H = 20 mm), the SW1 displayed a satisfactory durability with CA
values larger than 150° after rinse by 1000 ml simulated acid rain, and
there is no significant changes in sliding angle which is still under 10°.
In addition, the drop volume keep at 200 ml, and the CA values still
larger than 150° after H increased to 100 mm, and SA almost increased
to 20°. With the increasing of drop volume and drop height, the impulse
force of wood surface to withstand also increases, there may be a little
solution penetrated into the grooves, leading to the decrease of CA
and increase of SA for SW1. In general, the SW1 shows an excellent du-
rability after rinse by simulated acid rain.
3.3.2. Water resistance
The moisture content is one of the main factors affecting the
strength of wood. As a construction material, the water resistance of
wood is an important property. The water absorption (WA) of wood
can be calculated by the following equation:
WA %
ð Þ ¼ Mai−Mbi
ð Þ=Mbi 100 ð2Þ
where Mai is the quality of wood after immersion in water, Mbi is the
quality of wood before immersion in water. The results of water resis-
tance tests for pure wood and SW1 are shown in Fig. 6. When the sam-
ple immersion in water for 8 days, the WA of pure wood increased to
76.5%, while the WA of SW1 increased to 48.7%, and the WA increased
with the increase of immersion time. We can find that SW1 shows
good water resistance. This could be due to the silane-treatment, mak-
ing more surface areas of hygroscopic wood component covered by
the APTES film. In addition, silane is a kind of hydrophobic coating and
it could reduce the speed of moisture absorption. The superhydrophobic
Fig. 3. The WCA and WSA of (a) SW1 and (b) SW2. (c) CA of the SW1 and SW2 for the droplets with different pH values.
Fig. 4. The relationship between the water contact angles and the immersion time at varying pHs for the (a) SW1 and (b) SW2.
266 P. Cai et al. / Surface Coatings Technology 277 (2015) 262–269

6. coating on wood substrates is expected to prolong the lifetime of the
woodwork under a humid environment.
3.3.3. Self-cleaning
Self-cleaning effect is an important character of superhydrophobic
surface for their applications. The self-cleaning performance of the as-
prepared SW1 was demonstrated with white anatase and black graph-
ite as contaminant. The self-cleaning process is shown in Fig. 7a. A
sparse layer of contaminant power was sprinkled on the surface with
a tilting angle of about 5° and then a water droplet was dropped to
the contaminant surface. Immediately, the contaminant powder was
picked up and carried away by the water droplet, leaving behind a
clear surface. It was observed that the water droplet maintained a
spherical shape even after it has taken up the contaminant and one
small water droplet could clean up a large amount of contaminants.
This observation confirms that the as-prepared SW1 has a highly self-
cleaning effect.
To confirm the feasibility, five types of commonly used liquids, includ-
ing coffee, wine, milk, tea, and ink were used to examine surface repellen-
cy toward these liquids on the SW1. Fig. 7b shows these spherical droplets
sitting on SW1. The satisfactory result clearly demonstrates that this effi-
cient approach contributes significantly to anti-contamination coatings
on wood surfaces.
3.4. Application prospect
Considering the complex practical environments of industry, it is of
vital importance to investigate the feasibility of our method research. Cot-
ton textiles and filter paper, as additional products of wood have various
excellent properties such as flexibility, biodegradability, low cost and
density. Thus, superhydrophobic cotton textiles and superhydrophobic
filter paper have been made for oil/water separation in the same way.
As a model for separating the water and oil from their mixture, Fig. 8a
shows the separation process of the mixture with 30 ml oil and 30 ml
water on superhydrophobic cotton textile. The oil freely permeated
through the cotton textile, and then fell into the beaker beneath it. Mean-
while, more and more water was accumulated on the cotton textile sur-
face, and then decanted into the measuring cylinder, the separation
efficiency of superhydrophobic cotton textiles and superhydrophobic fil-
ter paper was shown in Table 2, it can be observed that nearly 100% of the
water was collected in the measuring cylinder, and high separation effi-
ciency for toluene, chloroform and n-heptane. Additionally, we also in-
vestigated the reusability of the cotton by measuring the oil volume
gather after wetting–drying–wetting cycles by oil such as toluene. As is
shown in Fig. 8b, the cotton textiles still have very high efficiency separa-
tion after ten times separation. It indicates that this superhydrophobic
cotton textile possesses an extensive application prospect in oil–water
separation. It can separate oil and water effectively and continuously
without using any other complex means.
Fig. 5. Water contact angle of (a) SW1 and (b) SW2 before and after treatment in various organic solvents for 100 h.
Fig. 6. The relationship between the water absorption and the immersion time in water for
SW1.
Fig. 7. (a) The time sequence of the self-cleaning process on the SW1 at a sliding angle
about 5°. (b ) Photograph of common household liquids on the SW1.
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P. Cai et al. / Surface Coatings Technology 277 (2015) 262–269

7. 4. Conclusions
In summary, two kinds of superhydrophobic wood were successfully
fabricated through the simple solution-immersion method in this study.
The adhesion mechanism between lauryl aldehyde and wood surface is
chemical bond, while the adhesion mechanism between lauric acid and
wood surface is physical adsorption. Compared to SW2, SW1 possesses
not only a better hydrophobicity but also an extraordinary stability
under corrosive liquids such as acidic and basic solutions, various organ-
ic solvents and simulated seawater. Additionally, SW1 shows an excel-
lent environmental adaptability like anticorrosion from simulated acid
rain, good water resistance and highly self-cleaning ability. Further-
more, cotton textiles and filter paper, as an additional product of
wood, were used to fabricate superhydrophobic materials under the
same condition, which shows high separation efficiency and good reus-
ability for oil/water separation. It is believed that this facile, low-cost
and large-area application method can offer an effective strategy and
promising industrial applications for fabricating superhydrophobic
coating on other additional product of wood.
Acknowledgments
The authors specially thank for the financial support of this work
from the National Natural Science Foundation of China (51103120).
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n-Heptane 87% 90%
Fig. 8. (a) Oil/water separation studies of the superhydrophobic cotton textile. For clarity, water and oil were dyed by methyl blue and Sudan III. (b) Separation capacity for toluene of the
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