21 Z. Wu, M. Liu, Modelling of ambipolar transport properties of
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(1996), 65–84, doi:10.1016/S0167-2738(96)00521-8
22 M. Marin{ek, S. Pejovnik, M. Ma~ek, Modelling of Electrical
Properties of Ni-YSZ Composites, J. Eur. Ceram. Soc., 27 (2007),
959–964, doi:10.1016/j.jeurceramsoc.2006.04.165
23 J. A. Quiblier, A new three-dimensional modeling technique for
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doi:10.1016/0021-9797(84)90481-8
24 H. S. Hong, U. S. Chae, S. T. Choo, The effect of ball milling
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331–334, doi:10.1016/j.jallcom.2006.01.131
25 J. R. Wilson, S. A. Barnett, Solid Oxide Fuel Cell Ni–YSZ Anodes:
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30 M. Schaffer, J. Wagner, B. Schaffer, M. Schmied, H. Mulders,
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782 Materiali in tehnologije / Materials and technology 51 (2017) 5, 775–782
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
H. Y. JIN et al.: A FACILE METHOD TO PREPARE SUPER-HYDROPHOBIC SURFACES ON SILICONE RUBBERS
783–787
A FACILE METHOD TO PREPARE SUPER-HYDROPHOBIC
SURFACES ON SILICONE RUBBERS
PREPROSTA METODA ZA PRIPRAVO SUPERHIDROFOBNIH
POVR[IN PRI SILIKONSKIH GUMAH
Hai Yun Jin1, Yu Feng Li1, Shi Chao Nie1, Peng Zhang1, Nai Kui Gao1, Wen Li2
1Xi’an Jiaotong University, State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an, 710049, China
2Hubei Polytechnic University, Hubei Key Laboratory of Mine Environmental Pollution Control & Remediation and School of Chemical and
Materials Engineering, Huangshi, 435003, PR China
lxfzzl@126.com
Prejem rokopisa – received: 2016-09-02; sprejem za objavo – accepted for publication: 2016-10-24
doi:10.17222/mit.2016.267
Fabricating large-scale super-hydrophobic surfaces for commercial applications is challenging due to certain limitations. In this
paper, a simple and inexpensive method is developed to fabricate super-hydrophobic surfaces on silicone rubbers. Rough micro-
structures were prepared on the mould’s inner surfaces and then sample super-hydrophobic surfaces on silicone rubbers with
different surface roughness were achieved using the standard moulding process. Furthermore, the effects of roughness on the
wettability were investigated. The results showed that by controlling the roughness, the fabricated surfaces exhibited a static
contact angle of 150.9° and a sliding angle of 8°. Finally, the property of hydrophobicity recovery for the silicone-rubber sam-
ples was also studied. The surfaces of the samples could recover well after a sand-blasting experiment. The proposed method is
low-cost, environmentally friendly and suggests promising industrial applications.
Keywords: thin films, coatings, chemical techniques, surface properties
Izdelava obse`nih superhidrofobnih povr{in za komercialne namene je zaradi dolo~enih omejitev zahtevna. V ~lanku je razvit
preprost in poceni na~in za izdelavo superhidrofobne povr{ine na silikonskih gumah. Grobe mikrostrukture so bile pripravljene
na notranjih povr{inah kalupa in nato je bila dose`ena vzor~na superhidrofobna povr{ina na silikonski gumi z razli~no hrapavo
povr{ino z uporabo standardnega postopka modeliranja. Nadalje so bili raziskani u~inki hrapavosti na omo~ljivost. Rezultati so
pokazali, da so s krmiljenjem hrapavosti izdelane povr{ine razstavljene pod stati~nim kontaktnim kotom 150.9° in drsnim kotom
8°. Nazadnje je bila preu~evana tudi lastnost okrevanja hidrofobnosti vzorcev silikonskih gum. Povr{ine vzorcev se lahko dobro
obnovijo tudi po poskusu s peskanjem. Predlagana metoda je poceni, okolju prijazna in ka`e obetavne mo`nosti apliciranja v
procese v industriji.
Klju~ne besede: tanke plasti, prevleke, kemijske tehnike, povr{inske lastnosti
1 INTRODUCTION
Superhydrophobic surfaces, with a water contact
angle (CA) greater than 150° and a sliding angle (SA)
less than 10°, have aroused increasing research interest
for their promising applications.1–6 By observing the
microstructure of a lotus leaf surface, it was found that
the combination of micro papilla and a thin wax film
leads to the self-cleaning properties.4 L. Jiang et al.1 dis-
covered that on top of the micro papilla also exist
branch-like nanostructures and pointed out that the
micro- and nanoscale hierarchical structures were the
fundamental mechanism for lotus leaf’s unique wetting
properties. There were two main measures to fabricate
superhydrophobic surfaces:
1) preparation of a rough surface followed by a low
free-energy material coating step,
2) creation of a rough surface from low-surface-energy
materials.1
Up to now, many approaches to fabricate rough sur-
faces had been developed, including the template
method7, phase separation8, self-assembly9, vapour-phase
deposition10, chemical etching11, laser etching12, hydro-
thermal method13, and electrospinning14. In the power
system, the surfaces of insulators always work under
high voltage and the sand-dust climate condition. How-
ever, some superhydrophobic coats (especially rubber-
based coatings) synthesized by techniques on large-area
and environmentally friendly cannot meet the operating
requirements of composite insulators.15–17 Therefore, it is
a good way to solve this problem by synthesizing a
superhydrophobic surface on the basis of not changing
the insulator material. Silicon rubber was a hydrophobic
material; therefore, a superhydrophobic surface could be
created by only forming a special nm-μm geometry
structure. The template method was a simple and con-
venient technique that could be used as a method to
prepare superhydrophobic surfaces, and the quality of
this method was easy to control; therefore, template
method was suited for industrial production.
In this study, to fabricate a superhydrophobic surface
on the composite insulators, a silicone-rubber super-
hydrophobic surface was developed with a facile tem-
plate method. The creation of a rough structure on the
inner surface of the mould and a special geotroy mor-
phology was prepared on the silicone-rubber surface
Materiali in tehnologije / Materials and technology 51 (2017) 5, 783–787 783
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
UDK 67.017:621.315.617:544.722.3 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 51(5)783(2017)
through a conventional moulding process. The surface
microstructures were investigated by a roughness tester
and scanning electron microscope (SEM). It was found
that the superhydrophobic silicone-rubber surface could
be attained by creating the appropriate roughness sur-
faces, which lead to the lotus-leaf-like surface morphol-
ogy. After samples suffered the artificial sandstorm
testing, the property of hydrophobicity recovery for
superhydrophobic and a common silicone-rubber surface
have also been studied in this paper.
2 EXPERIMENTAL PART
Templates with different rough structures were pre-
pared first. Silicon carbide particles of (63, 21, 15, and
10.5) μm in diameter were obtained by using test sieves
of 80, 240, 600, 800 and 1200 mesh, respectively. A uni-
form layer of resin binder-epoxy resin was sprayed on
the inner surface of a cubic mould with dimensions of 3
cm × 3 cm × 3 cm after treating with a silane coupling
agent N--aminoethyl--aminopropyl trimethoxysilane.
The prepared silicon carbide particles were evenly
sprayed on the inner surface of the mould and dried at
room temperature. Then rough silicon rubber samples
were prepared through a conventional moulding process.
Liquid silicone rubber was poured into the mould, the
mould was taken off after consolidation, and thus sili-
cone-rubber surfaces with different surface morphologies
were obtained. To avoid the superhydrophobic surface
being destroyed during the mould unloading, the moulds
were treated with a release agent(methyl-silicone oil).
For a comparison, the smooth silicone rubber was
prepared with a smooth mould.
To analyses the morphology and microstructures of
the sample surfaces, SEM and a roughness tester were
used. The morphological characterization was observed
with a SEM (VE-9800, Keyence). The surface roughness
Ra was measured with a handhold roughness tester
(TR200, Times Run Bao). The roughness tester was
placed at 20 different locations of the sample surface un-
der investigation and the average value was taken as the
surface roughness.
The water contact angles were investigated using a
measurement system (JC2000C4, POWEREACH). Be-
fore the test the samples were washed with deionized
water and ethanol, respectively, and then naturally dried.
Five different locations of the sample surface were mea-
sured, and the average value was used.
The property of hydrophobicity recovery for both the
superhydrophobic and the common silicone-rubber sur-
face were tested in the artificial experimental platform,
and the sand-dust sample was also prepared, as described
in 18. Samples of superhydrophobic silicone rubber and
the common silicone rubber were placed horizontally in
the experimental platform. The surfaces of the samples
and the wind direction were parallel. The wind speed
was 15m/s. The samples were in the artificial sandstorm
for 1 h. To accelerate the process of hydrophobicity re-
covery, the heat treatment for the sample was carried out
in an oven at 75 °C.
3 RESULTS AND DISCUSSION
Figure 1a to 1f show SEM micrographs of surface
morphologies for the different silicone-rubber surfaces.
A very flat microstructure can be seen from the surface
prepared with the smooth template (Figure 1a). After
preparing with templates, the surfaces have spongy-like
rough structures and this confirmed that the morphology
of the mould surface was successfully replicated. It can
be seen that rough structure units (number and decrease
in scale) increase with decreasing silicon carbide particle
size. The silicone-rubber surface prepared with a tem-
plate of particle size 63 μm has an average diameter of
200 μm irregular protuberances and pits (Figure 1b), the
surface distributes on average a diameter of 100 μm ir-
regular papilla (Figure 1c), and the surface prepared
with template of particle size of 15 μm in diameter has a
diameter of about 40 μm irregular pits and protuberances
(Figure 1d). Figure 1e to 1f are higher-resolution
micrographs of Figure 1d. Figure 1f and show that the
randomly distributed papilla morphology (observed in
Figure 1e) consists of sub-micron structures, which
implies two-length-scale hierarchical structure on the
surface. Therefore, the Cassie-Baxter superhydrophobic
state was well formed.
H. Y. JIN et al.: A FACILE METHOD TO PREPARE SUPER-HYDROPHOBIC SURFACES ON SILICONE RUBBERS
784 Materiali in tehnologije / Materials and technology 51 (2017) 5, 783–787
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 1: SEM micrographs of surface prepared with templates of dif-
ferent diameter silicon carbide particles: a) smooth, b) 63 μm,
c) 21 μm, d) 15 μm, e) the high magnification of d), and f) the high
magnification of (e)
Figure 2 shows the roughness of the surface mor-
phology. The surface roughness of the smooth silicone
rubber surface was 0.42 μm. When the templates are
made by different silicon carbide particles of (10.5, 15,
21, and 63) μm in diameter, the surface roughness of the
samples made by different templates are (10.88, 14.63,
17.32 and 33.61) μm, respectively. The results show that,
after roughening with a rough template, the surface
roughness of the silicone rubber increases with the in-
creasing particle size of the sprayed silicon carbide.
Figure 3 shows the relationship between the surface
wettability and the surface roughness. It is clear that the
contact angle of the smooth silicone rubber surface is
110.2° and the sliding angle is about 90°. While rough-
ening with rough templates, the surface wettability is
greatly improved (the contact angle is larger than 140°
and the sliding angle is from 8° to 50°). The higher
contact angle of the rough silicone-rubber surface can be
attributed to the formation of the Wenzel wetting state
(Figure 4a). According to Wenzel model (cos * = r cos
, where * is Wenzel apparent contact angle,  is the
intrinsic contact angle of the ideal smooth material,
which also called as Young’s contact angle, and r is the
ratio of the actual area to the projected area), rough
structures can amplify the natural wettability tendency of
the surface. Since silicone rubber is hydrophobic, the
surface hydrophobic property will be improved by
roughening the surface; its new contact angle becomes
greater than the intrinsic contact angle. The contact angle
reaches to 150.9° with a very small sliding angle of 8o
for samples with a surface roughness of 14.63 μm. This
can be explained by the formation of the Cassie-Baxter
wetting state (Figure 4b), for it has a lotus-leaf-like
surface morphology (Figure 1d to 1f). It is because of
that that there is such a micro-submicron hierarchical
structure on samples, which is like the structure of the
lotus leaf.1,4 If a water droplet is placed upon the surface,
air can be entrapped in both the hollows and interstices,
resulting in the formation of a high area fraction of
air-liquid interfaces. According to the Cassie-Baxter
equation (cos a = f1 cos – f2, where a is the apparent
contact angle on a rough surface, f1 is the area fraction of
the solid-liquid interface, and f2 is area fraction of the
air-liquid interface), the contact angle can larger than
150° when the rough surface attains a large area fraction
of air-liquid interface. With regards to the sliding angle,
a surface exhibiting the Wenzel wetting state usually
shows a larger sliding angle due to the pinning effects
(Figure 4a). In contrast, a surface following the regime
of the Cassie–Baxter wetting state (Figure 4b) allows a
water droplet to roll off easily with a sliding angle of less
than 10°.
Figure 3 shows that surface roughness plays an im-
portant role in the surface wettability. Since all the sili-
cone rubber samples are prepared with a similar template
structure (but different roughness), the samples present a
similar surface morphology (Figure 1b to 1d). For
samples with surface roughness Ra of 10.88 μm and
14.63 μm, the contact angle exceeds 150°, with a negli-
gible sliding angle of about 8°. The contact angles
reaches to a maximum value of 151.8°, when the surface
roughness is 10.88 μm. When the surface roughness is
larger than 10.88 μm, the contact angles decrease with
increasing surface roughness. For the samples with a
surface roughness (Ra) of 17.32 μm and 33.61 μm, the
contact angles are 146.9° and 140.8° respectively, while
both of them show a sliding angle of about 50°. It is
known that the micro-scale and nano-scale hierarchical
structures affect the contact angle greatly. The micro-
scale and nano-scale hierarchical structures can be
H. Y. JIN et al.: A FACILE METHOD TO PREPARE SUPER-HYDROPHOBIC SURFACES ON SILICONE RUBBERS
Materiali in tehnologije / Materials and technology 51 (2017) 5, 783–787 785
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 4: Various wetting state model sketch of a droplet on a rough
surface: a) Wezel state, b) Cassie-Baxer state and c) combined
Cassie-Baxter/Wenzel state
Figure 3: Relationship between static contact angle and surface
roughness
Figure 2: Relationship between particle size and surface roughness Ra
through a conventional moulding process. The surface
microstructures were investigated by a roughness tester
and scanning electron microscope (SEM). It was found
that the superhydrophobic silicone-rubber surface could
be attained by creating the appropriate roughness sur-
faces, which lead to the lotus-leaf-like surface morphol-
ogy. After samples suffered the artificial sandstorm
testing, the property of hydrophobicity recovery for
superhydrophobic and a common silicone-rubber surface
have also been studied in this paper.
2 EXPERIMENTAL PART
Templates with different rough structures were pre-
pared first. Silicon carbide particles of (63, 21, 15, and
10.5) μm in diameter were obtained by using test sieves
of 80, 240, 600, 800 and 1200 mesh, respectively. A uni-
form layer of resin binder-epoxy resin was sprayed on
the inner surface of a cubic mould with dimensions of 3
cm × 3 cm × 3 cm after treating with a silane coupling
agent N--aminoethyl--aminopropyl trimethoxysilane.
The prepared silicon carbide particles were evenly
sprayed on the inner surface of the mould and dried at
room temperature. Then rough silicon rubber samples
were prepared through a conventional moulding process.
Liquid silicone rubber was poured into the mould, the
mould was taken off after consolidation, and thus sili-
cone-rubber surfaces with different surface morphologies
were obtained. To avoid the superhydrophobic surface
being destroyed during the mould unloading, the moulds
were treated with a release agent(methyl-silicone oil).
For a comparison, the smooth silicone rubber was
prepared with a smooth mould.
To analyses the morphology and microstructures of
the sample surfaces, SEM and a roughness tester were
used. The morphological characterization was observed
with a SEM (VE-9800, Keyence). The surface roughness
Ra was measured with a handhold roughness tester
(TR200, Times Run Bao). The roughness tester was
placed at 20 different locations of the sample surface un-
der investigation and the average value was taken as the
surface roughness.
The water contact angles were investigated using a
measurement system (JC2000C4, POWEREACH). Be-
fore the test the samples were washed with deionized
water and ethanol, respectively, and then naturally dried.
Five different locations of the sample surface were mea-
sured, and the average value was used.
The property of hydrophobicity recovery for both the
superhydrophobic and the common silicone-rubber sur-
face were tested in the artificial experimental platform,
and the sand-dust sample was also prepared, as described
in 18. Samples of superhydrophobic silicone rubber and
the common silicone rubber were placed horizontally in
the experimental platform. The surfaces of the samples
and the wind direction were parallel. The wind speed
was 15m/s. The samples were in the artificial sandstorm
for 1 h. To accelerate the process of hydrophobicity re-
covery, the heat treatment for the sample was carried out
in an oven at 75 °C.
3 RESULTS AND DISCUSSION
Figure 1a to 1f show SEM micrographs of surface
morphologies for the different silicone-rubber surfaces.
A very flat microstructure can be seen from the surface
prepared with the smooth template (Figure 1a). After
preparing with templates, the surfaces have spongy-like
rough structures and this confirmed that the morphology
of the mould surface was successfully replicated. It can
be seen that rough structure units (number and decrease
in scale) increase with decreasing silicon carbide particle
size. The silicone-rubber surface prepared with a tem-
plate of particle size 63 μm has an average diameter of
200 μm irregular protuberances and pits (Figure 1b), the
surface distributes on average a diameter of 100 μm ir-
regular papilla (Figure 1c), and the surface prepared
with template of particle size of 15 μm in diameter has a
diameter of about 40 μm irregular pits and protuberances
(Figure 1d). Figure 1e to 1f are higher-resolution
micrographs of Figure 1d. Figure 1f and show that the
randomly distributed papilla morphology (observed in
Figure 1e) consists of sub-micron structures, which
implies two-length-scale hierarchical structure on the
surface. Therefore, the Cassie-Baxter superhydrophobic
state was well formed.
H. Y. JIN et al.: A FACILE METHOD TO PREPARE SUPER-HYDROPHOBIC SURFACES ON SILICONE RUBBERS
784 Materiali in tehnologije / Materials and technology 51 (2017) 5, 783–787
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 1: SEM micrographs of surface prepared with templates of dif-
ferent diameter silicon carbide particles: a) smooth, b) 63 μm,
c) 21 μm, d) 15 μm, e) the high magnification of d), and f) the high
magnification of (e)
Figure 2 shows the roughness of the surface mor-
phology. The surface roughness of the smooth silicone
rubber surface was 0.42 μm. When the templates are
made by different silicon carbide particles of (10.5, 15,
21, and 63) μm in diameter, the surface roughness of the
samples made by different templates are (10.88, 14.63,
17.32 and 33.61) μm, respectively. The results show that,
after roughening with a rough template, the surface
roughness of the silicone rubber increases with the in-
creasing particle size of the sprayed silicon carbide.
Figure 3 shows the relationship between the surface
wettability and the surface roughness. It is clear that the
contact angle of the smooth silicone rubber surface is
110.2° and the sliding angle is about 90°. While rough-
ening with rough templates, the surface wettability is
greatly improved (the contact angle is larger than 140°
and the sliding angle is from 8° to 50°). The higher
contact angle of the rough silicone-rubber surface can be
attributed to the formation of the Wenzel wetting state
(Figure 4a). According to Wenzel model (cos * = r cos
, where * is Wenzel apparent contact angle,  is the
intrinsic contact angle of the ideal smooth material,
which also called as Young’s contact angle, and r is the
ratio of the actual area to the projected area), rough
structures can amplify the natural wettability tendency of
the surface. Since silicone rubber is hydrophobic, the
surface hydrophobic property will be improved by
roughening the surface; its new contact angle becomes
greater than the intrinsic contact angle. The contact angle
reaches to 150.9° with a very small sliding angle of 8o
for samples with a surface roughness of 14.63 μm. This
can be explained by the formation of the Cassie-Baxter
wetting state (Figure 4b), for it has a lotus-leaf-like
surface morphology (Figure 1d to 1f). It is because of
that that there is such a micro-submicron hierarchical
structure on samples, which is like the structure of the
lotus leaf.1,4 If a water droplet is placed upon the surface,
air can be entrapped in both the hollows and interstices,
resulting in the formation of a high area fraction of
air-liquid interfaces. According to the Cassie-Baxter
equation (cos a = f1 cos – f2, where a is the apparent
contact angle on a rough surface, f1 is the area fraction of
the solid-liquid interface, and f2 is area fraction of the
air-liquid interface), the contact angle can larger than
150° when the rough surface attains a large area fraction
of air-liquid interface. With regards to the sliding angle,
a surface exhibiting the Wenzel wetting state usually
shows a larger sliding angle due to the pinning effects
(Figure 4a). In contrast, a surface following the regime
of the Cassie–Baxter wetting state (Figure 4b) allows a
water droplet to roll off easily with a sliding angle of less
than 10°.
Figure 3 shows that surface roughness plays an im-
portant role in the surface wettability. Since all the sili-
cone rubber samples are prepared with a similar template
structure (but different roughness), the samples present a
similar surface morphology (Figure 1b to 1d). For
samples with surface roughness Ra of 10.88 μm and
14.63 μm, the contact angle exceeds 150°, with a negli-
gible sliding angle of about 8°. The contact angles
reaches to a maximum value of 151.8°, when the surface
roughness is 10.88 μm. When the surface roughness is
larger than 10.88 μm, the contact angles decrease with
increasing surface roughness. For the samples with a
surface roughness (Ra) of 17.32 μm and 33.61 μm, the
contact angles are 146.9° and 140.8° respectively, while
both of them show a sliding angle of about 50°. It is
known that the micro-scale and nano-scale hierarchical
structures affect the contact angle greatly. The micro-
scale and nano-scale hierarchical structures can be
H. Y. JIN et al.: A FACILE METHOD TO PREPARE SUPER-HYDROPHOBIC SURFACES ON SILICONE RUBBERS
Materiali in tehnologije / Materials and technology 51 (2017) 5, 783–787 785
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 4: Various wetting state model sketch of a droplet on a rough
surface: a) Wezel state, b) Cassie-Baxer state and c) combined
Cassie-Baxter/Wenzel state
Figure 3: Relationship between static contact angle and surface
roughness
Figure 2: Relationship between particle size and surface roughness Ra
quantified by the surface roughness; therefore, the effect
of surface structures on the contact angle can be studied
by the surface roughness.19 Compared with the contact
angle, the sliding angle is more affected by the surface
roughness. This can be attributed to the formation of the
combined Cassie-Baxter and Wenzel wetting state model
(Figure 4c).20,21 As seen, the area fraction of air-liquid
interfaces from the combined Cassie-Baxter and Wenzel
wetting state model changes little (compared with
Cassie-Baxter wetting state model); therefore, the con-
tact angle will be larger than 140°. However, the sliding
angle is greatly increased due to a certain extent by the
pinning effects (Figure 4c). With respect to promising
applications, such as anti-icing of superhydrophobic sur-
faces, both the contact angle and the small sliding angle
are very important; therefore, the sliding angle also plays
a important role.22 Superhydrophobic surfaces with
negligible sliding angle can be obtained by controlling
the surface structure and the roughness.
Figure 5 shows the changes of the contact angle after
the sandstorm experiment and the hydrophobicity recov-
ery experiment. Because of the effects of the sand-dust,
both of the contact angles decrease by approximately
20°. At the beginning of the recovering process, the hyd-
rophobicity of samples recover quickly. Then the speed
of the recovery slows down. After 24 h in a high-tem-
perature treatment, the hydrophobicities of both super-
hydrophobic and common silicone rubber have basically
recovered to the level of the primary sample.
The sand-dust on the silicone rubber is hydrophilic,
which results in hydrophobicity degradation of the
samples. Inside the silicone rubber, the large molecules
polysiloxane are cracked into smaller molecules poly-
siloxane. And the high temperature can accelerate the
cracking process. The small molecules polysiloxane with
a low surface tension can migrate to the surface of the
silicone rubber and cover the sand-dust particles.23,24
Therefore, the hydrophobicity can be recovered after the
high-temperature treatment. Considering that the contact
angle of the superhydrophobic silicone rubber has recov-
ered to almost 150°, it shows that the micro-submicron
hierarchical structure of superhydrophobic surfaces can
almost not be destroyed.
4 CONCLUSIONS
Superhydrophobic surfaces were successfully fabri-
cated on silicone rubbers through a facile template
method. The contact angle for the surfaces can reach a
maximum of 151.8° (sliding angle about 8°) with a sur-
face roughness of 10.88 μm. When the surface roughness
is larger than 10.88 μm the contact angle decreased with
increasing roughness, and when the surface roughness is
less than 10.88 μm, the contact angle increased with
increasing roughness. The micro/sub-micron hierarchical
structures of the surface were responsible for the high
water contact angle and the low sliding angle. The
wetting ability of the various surface roughness was
different, and it could be explained by the different
wetting state model. The sandstorm testing and the
hydrophobicity experiment showed that the contact angle
of both superhydrophobic and the common silicone
rubber sample could recover.
Acknowledgments
This research was financially supported by the Na-
tional Natural Science Foundation of China (No.
51272208), the Natural Science Foundation of Hubei
Province (2010CDA026), the Key Program of Hubei
Provincial Department of Education (Z20104401), the
Outstanding Scientific and Technological Innovation
Team Project of Universities in Hubei Province
(T201423), and the Talent Program of Hubei Polytechnic
University (11yjz04R).
5 REFERENCES
1 L. Feng, S. Li, Y. Li, H. Li, L. Zhang, J. Zhai, Y. Song, B. Liu, L.
Jiang, D. Zhu, Super-hydrophobic surfaces: From natural to artificial,
Advanced Materials, 14 (2002) 24, 1857–1860, doi:10.1002/adma.
200290020
2 K. K. Varanasi, M. Hsu, N. Bhate, W. Yang, T. Deng, Spatial Control
in the Heterogeneous Nucleation of Water, Applied Physics Letters,
95 (2009) 9, 094101, doi:10.1063/1.3200951
3 L. Cao, A. K. Jones, V. K. Sikka, J. Z. Wu, D. Gao, Anti-Icing
Superhydrophobic Coatings, Langmuir, 25 (2009) 21, 12444–12448,
doi:10.1021/la902882b
4 W. Barthlott, C. Neinhuis, Purity of the sacred lotus, or escape from
contamination in biological surfaces, Planta, 202 (1997) 1, 1–8,
doi:10.1007/s004250050096
5 F. Arianpour, M. Farzaneh, S. A. Kulinich, Hydrophobic and ice-re-
tarding properties of doped silicone rubber coatings, Applied Surface
Science, 265 (2013), 546–552, doi:10.1016/j.apsusc.2012.11.042
6 J. Li, Y. Zhao, J. Hu, L. Shu, X. Shi, Anti-icing Performance of a
Superhydrophobic PDMS/Modified Nano-silica Hybrid Coating for
Insulators, Journal of Adhesion Science and Technology, 26 (2012)
4–5, 665–679, doi:10.1163/016942411X574826
H. Y. JIN et al.: A FACILE METHOD TO PREPARE SUPER-HYDROPHOBIC SURFACES ON SILICONE RUBBERS
786 Materiali in tehnologije / Materials and technology 51 (2017) 5, 783–787
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 5: The recovery curve for the hydrophobicity of the sili-
cone-rubber samples
7 M. Jin, M. Liao, J. Zhai, L. Jiang, Super-hydrophobic polystyrene
films prepared via pattern transformation, Acta Chimica Sinica, 66
(2008) 1, 145–148, doi:10.3321/j.issn:0567-7351.2008.01.025
8 Q. Xie, G. Fan, N. Zhao, X. Guo, J. Xu, J. Dong, L. Zhang, Y.
Zhang, C. Han, Facile creation of a bionic super-hydrophobic block
copolymer surface, Advanced Materials, 16 (2004) 20, 1830–1833,
doi:10.1002/adma.200400074
9 J. Genzer, K. Efimenko, Creating long-lived super-hydrophobic poly-
mer surfaces through mechanically assembled monolayers, Science,
290 (2000) 5499, 2130–2133, doi:10.1126/science.290.5499.2130
10 A. Hozumi, O. Takai, Preparation of ultra water-repellent films by
microwave plasma-enhanced CVD, Thin Solid Films, 303 (1997)
1–2, 222–225, doi:10.1016/S0040-6090(97)00076-X
11 D. Xie, W. Li. A novel simple approach to preparation of super-
hydrophobic surface of aluminum alloys, Applied Surface Science,
258 (2011) 3, 1004–1007, doi: 10.1016/j.apsusc.2011.07.104
12 T. Sun, G. Wang, L. Feng, B. Liu, Y. Ma, L. Jiang, D. Zhu,
Reversible switching between super-hydrophilicity and super-hydro-
phboicity, Angewandte Chemie International Edition, 43 (2004) 3,
357–360, doi:10.1002/anie.200352565
13 X. Feng, L. Feng, M. Jin, J. Zhai, L. Jiang, D. Zhu, Reversible
super-hydrophobicity to super-hydrophilicity transition of aligned
ZnO nanorod films, Journal of the American Chemical Society, 126
(2004) 1, 62–63, doi:10.1021/ja038636o
14 L. Jiang, Y. Zhao, J. Zhai, A lotus-leaf-like superhydrophobic sur-
face: a porous microsphere/nanofiber composite film prepared by
electrohydrodynamics, Angewandte Chemie International Edition,
43 (2004) 33, 4338–4341, doi:10.1002/anie.200460333
15 M. K. Tiwari, I. S. Bayer, G. M. Jursich, T. M. Schutzius, C. M.
Megaridis, Highly Liquid-Repellent, Large-Area, Nanostructured
Poly(vinylidene fluoride)/Poly(ethyl 2-cyanoacrylate) Composite
Coatings: Particle Filler Effects, ACS applied materials & interfaces,
2 (2010) 4, 1114–1119, doi:10.1021/am900894n
16 T. M. Schutzius, I. S. Bayer, J. Qin, D. Waldroup, C. M. Megaridis,
Water-Based, Nonfluorinated Dispersions for Environmentally Be-
nign, Large-Area, Superhydrophobic Coatings, ACS applied mate-
rials & interfaces, 5 (2013) 24, 13419–13425, doi:10.1021/
am4043307
17 E. Bormashenko, V. Goldshtein, R. Barayev, T. Stein, G. Whyman,
R. Pogreb, Z. Barkay, D. Aurbach, Robust method of manufacturing
rubber waste-based water repellent surfaces, Polymers for Advanced
Technologies, 20 (2009) 7, 650–653, doi:10.1002/pat.1323
18 B. He, G. Zhang, B. Chen, N. Gao, Y. Li, Z. Peng, H. Jin, The
influence of the sand-dust environment on air-gap breakdown
discharge characteristics of the plate-to-plate electrode, Science
China Physics, Mechanics and Astronomy, 53 (2010) 3, 458–464,
doi:10.1007/s11433-010-0078-1
19 X. Shi, T. A. Nguyen, Z. Suo, J. Wu, J. Gong, R. Avci, Electrochemi-
cal and mechanical properties of superhydrophobic aluminum sub-
strates modified with nano-silica and fluorosilane, Surface and Coat-
ings Technology, 206 (2012) 17, 3700–3713, doi:10.1016/j.surfcoat.
2012.02.058
20 X. Feng, L. Jiang, Design and creation of superwetting/antiwetting
surfaces, Advanced Material, 18 (2006) 23, 3063–3078, doi:10.1002/
adma.200501961
21 C. W. Yang, F. He, P. F. Hao, The apparent contact angle of water
droplet on the micro-structured hydrophobic surface, Science China
Chemistry, 53 (2010) 4, 912–916, doi:10.1007/s11426-010-0115-y
22 S. A. Kulinich, M. Farzaneh, How Wetting Hysteresis Influences Ice
Adhesion Strength on Superhydrophobic Surfaces. Langmuir, 25
(2009) 16, 8854–8856, doi:10.1021/la901439c
23 J. W. Chang, R. S. Gorur, Surface recovery of silicone rubber used
for HV outdoor insulation, IEEE Transactions on Dielectrics and
Electrical Insulation, 1 (1994) 6, 1039–1046, doi:10.1109/94.368659
24 T. Tokoro, R. Hackam, Loss and recovery of hydrophobicity and sur-
face energy of HTV silicone rubber, IEEE Transactions on Dielec-
trics and Electrical Insulation, 8 (2001) 6, 1088–1097,
doi:10.1109/94.971469
H. Y. JIN et al.: A FACILE METHOD TO PREPARE SUPER-HYDROPHOBIC SURFACES ON SILICONE RUBBERS
Materiali in tehnologije / Materials and technology 51 (2017) 5, 783–787 787
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
quantified by the surface roughness; therefore, the effect
of surface structures on the contact angle can be studied
by the surface roughness.19 Compared with the contact
angle, the sliding angle is more affected by the surface
roughness. This can be attributed to the formation of the
combined Cassie-Baxter and Wenzel wetting state model
(Figure 4c).20,21 As seen, the area fraction of air-liquid
interfaces from the combined Cassie-Baxter and Wenzel
wetting state model changes little (compared with
Cassie-Baxter wetting state model); therefore, the con-
tact angle will be larger than 140°. However, the sliding
angle is greatly increased due to a certain extent by the
pinning effects (Figure 4c). With respect to promising
applications, such as anti-icing of superhydrophobic sur-
faces, both the contact angle and the small sliding angle
are very important; therefore, the sliding angle also plays
a important role.22 Superhydrophobic surfaces with
negligible sliding angle can be obtained by controlling
the surface structure and the roughness.
Figure 5 shows the changes of the contact angle after
the sandstorm experiment and the hydrophobicity recov-
ery experiment. Because of the effects of the sand-dust,
both of the contact angles decrease by approximately
20°. At the beginning of the recovering process, the hyd-
rophobicity of samples recover quickly. Then the speed
of the recovery slows down. After 24 h in a high-tem-
perature treatment, the hydrophobicities of both super-
hydrophobic and common silicone rubber have basically
recovered to the level of the primary sample.
The sand-dust on the silicone rubber is hydrophilic,
which results in hydrophobicity degradation of the
samples. Inside the silicone rubber, the large molecules
polysiloxane are cracked into smaller molecules poly-
siloxane. And the high temperature can accelerate the
cracking process. The small molecules polysiloxane with
a low surface tension can migrate to the surface of the
silicone rubber and cover the sand-dust particles.23,24
Therefore, the hydrophobicity can be recovered after the
high-temperature treatment. Considering that the contact
angle of the superhydrophobic silicone rubber has recov-
ered to almost 150°, it shows that the micro-submicron
hierarchical structure of superhydrophobic surfaces can
almost not be destroyed.
4 CONCLUSIONS
Superhydrophobic surfaces were successfully fabri-
cated on silicone rubbers through a facile template
method. The contact angle for the surfaces can reach a
maximum of 151.8° (sliding angle about 8°) with a sur-
face roughness of 10.88 μm. When the surface roughness
is larger than 10.88 μm the contact angle decreased with
increasing roughness, and when the surface roughness is
less than 10.88 μm, the contact angle increased with
increasing roughness. The micro/sub-micron hierarchical
structures of the surface were responsible for the high
water contact angle and the low sliding angle. The
wetting ability of the various surface roughness was
different, and it could be explained by the different
wetting state model. The sandstorm testing and the
hydrophobicity experiment showed that the contact angle
of both superhydrophobic and the common silicone
rubber sample could recover.
Acknowledgments
This research was financially supported by the Na-
tional Natural Science Foundation of China (No.
51272208), the Natural Science Foundation of Hubei
Province (2010CDA026), the Key Program of Hubei
Provincial Department of Education (Z20104401), the
Outstanding Scientific and Technological Innovation
Team Project of Universities in Hubei Province
(T201423), and the Talent Program of Hubei Polytechnic
University (11yjz04R).
5 REFERENCES
1 L. Feng, S. Li, Y. Li, H. Li, L. Zhang, J. Zhai, Y. Song, B. Liu, L.
Jiang, D. Zhu, Super-hydrophobic surfaces: From natural to artificial,
Advanced Materials, 14 (2002) 24, 1857–1860, doi:10.1002/adma.
200290020
2 K. K. Varanasi, M. Hsu, N. Bhate, W. Yang, T. Deng, Spatial Control
in the Heterogeneous Nucleation of Water, Applied Physics Letters,
95 (2009) 9, 094101, doi:10.1063/1.3200951
3 L. Cao, A. K. Jones, V. K. Sikka, J. Z. Wu, D. Gao, Anti-Icing
Superhydrophobic Coatings, Langmuir, 25 (2009) 21, 12444–12448,
doi:10.1021/la902882b
4 W. Barthlott, C. Neinhuis, Purity of the sacred lotus, or escape from
contamination in biological surfaces, Planta, 202 (1997) 1, 1–8,
doi:10.1007/s004250050096
5 F. Arianpour, M. Farzaneh, S. A. Kulinich, Hydrophobic and ice-re-
tarding properties of doped silicone rubber coatings, Applied Surface
Science, 265 (2013), 546–552, doi:10.1016/j.apsusc.2012.11.042
6 J. Li, Y. Zhao, J. Hu, L. Shu, X. Shi, Anti-icing Performance of a
Superhydrophobic PDMS/Modified Nano-silica Hybrid Coating for
Insulators, Journal of Adhesion Science and Technology, 26 (2012)
4–5, 665–679, doi:10.1163/016942411X574826
H. Y. JIN et al.: A FACILE METHOD TO PREPARE SUPER-HYDROPHOBIC SURFACES ON SILICONE RUBBERS
786 Materiali in tehnologije / Materials and technology 51 (2017) 5, 783–787
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 5: The recovery curve for the hydrophobicity of the sili-
cone-rubber samples
7 M. Jin, M. Liao, J. Zhai, L. Jiang, Super-hydrophobic polystyrene
films prepared via pattern transformation, Acta Chimica Sinica, 66
(2008) 1, 145–148, doi:10.3321/j.issn:0567-7351.2008.01.025
8 Q. Xie, G. Fan, N. Zhao, X. Guo, J. Xu, J. Dong, L. Zhang, Y.
Zhang, C. Han, Facile creation of a bionic super-hydrophobic block
copolymer surface, Advanced Materials, 16 (2004) 20, 1830–1833,
doi:10.1002/adma.200400074
9 J. Genzer, K. Efimenko, Creating long-lived super-hydrophobic poly-
mer surfaces through mechanically assembled monolayers, Science,
290 (2000) 5499, 2130–2133, doi:10.1126/science.290.5499.2130
10 A. Hozumi, O. Takai, Preparation of ultra water-repellent films by
microwave plasma-enhanced CVD, Thin Solid Films, 303 (1997)
1–2, 222–225, doi:10.1016/S0040-6090(97)00076-X
11 D. Xie, W. Li. A novel simple approach to preparation of super-
hydrophobic surface of aluminum alloys, Applied Surface Science,
258 (2011) 3, 1004–1007, doi: 10.1016/j.apsusc.2011.07.104
12 T. Sun, G. Wang, L. Feng, B. Liu, Y. Ma, L. Jiang, D. Zhu,
Reversible switching between super-hydrophilicity and super-hydro-
phboicity, Angewandte Chemie International Edition, 43 (2004) 3,
357–360, doi:10.1002/anie.200352565
13 X. Feng, L. Feng, M. Jin, J. Zhai, L. Jiang, D. Zhu, Reversible
super-hydrophobicity to super-hydrophilicity transition of aligned
ZnO nanorod films, Journal of the American Chemical Society, 126
(2004) 1, 62–63, doi:10.1021/ja038636o
14 L. Jiang, Y. Zhao, J. Zhai, A lotus-leaf-like superhydrophobic sur-
face: a porous microsphere/nanofiber composite film prepared by
electrohydrodynamics, Angewandte Chemie International Edition,
43 (2004) 33, 4338–4341, doi:10.1002/anie.200460333
15 M. K. Tiwari, I. S. Bayer, G. M. Jursich, T. M. Schutzius, C. M.
Megaridis, Highly Liquid-Repellent, Large-Area, Nanostructured
Poly(vinylidene fluoride)/Poly(ethyl 2-cyanoacrylate) Composite
Coatings: Particle Filler Effects, ACS applied materials & interfaces,
2 (2010) 4, 1114–1119, doi:10.1021/am900894n
16 T. M. Schutzius, I. S. Bayer, J. Qin, D. Waldroup, C. M. Megaridis,
Water-Based, Nonfluorinated Dispersions for Environmentally Be-
nign, Large-Area, Superhydrophobic Coatings, ACS applied mate-
rials & interfaces, 5 (2013) 24, 13419–13425, doi:10.1021/
am4043307
17 E. Bormashenko, V. Goldshtein, R. Barayev, T. Stein, G. Whyman,
R. Pogreb, Z. Barkay, D. Aurbach, Robust method of manufacturing
rubber waste-based water repellent surfaces, Polymers for Advanced
Technologies, 20 (2009) 7, 650–653, doi:10.1002/pat.1323
18 B. He, G. Zhang, B. Chen, N. Gao, Y. Li, Z. Peng, H. Jin, The
influence of the sand-dust environment on air-gap breakdown
discharge characteristics of the plate-to-plate electrode, Science
China Physics, Mechanics and Astronomy, 53 (2010) 3, 458–464,
doi:10.1007/s11433-010-0078-1
19 X. Shi, T. A. Nguyen, Z. Suo, J. Wu, J. Gong, R. Avci, Electrochemi-
cal and mechanical properties of superhydrophobic aluminum sub-
strates modified with nano-silica and fluorosilane, Surface and Coat-
ings Technology, 206 (2012) 17, 3700–3713, doi:10.1016/j.surfcoat.
2012.02.058
20 X. Feng, L. Jiang, Design and creation of superwetting/antiwetting
surfaces, Advanced Material, 18 (2006) 23, 3063–3078, doi:10.1002/
adma.200501961
21 C. W. Yang, F. He, P. F. Hao, The apparent contact angle of water
droplet on the micro-structured hydrophobic surface, Science China
Chemistry, 53 (2010) 4, 912–916, doi:10.1007/s11426-010-0115-y
22 S. A. Kulinich, M. Farzaneh, How Wetting Hysteresis Influences Ice
Adhesion Strength on Superhydrophobic Surfaces. Langmuir, 25
(2009) 16, 8854–8856, doi:10.1021/la901439c
23 J. W. Chang, R. S. Gorur, Surface recovery of silicone rubber used
for HV outdoor insulation, IEEE Transactions on Dielectrics and
Electrical Insulation, 1 (1994) 6, 1039–1046, doi:10.1109/94.368659
24 T. Tokoro, R. Hackam, Loss and recovery of hydrophobicity and sur-
face energy of HTV silicone rubber, IEEE Transactions on Dielec-
trics and Electrical Insulation, 8 (2001) 6, 1088–1097,
doi:10.1109/94.971469
H. Y. JIN et al.: A FACILE METHOD TO PREPARE SUPER-HYDROPHOBIC SURFACES ON SILICONE RUBBERS
Materiali in tehnologije / Materials and technology 51 (2017) 5, 783–787 787
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS