U.S. patent application number 16/679144 was filed with the patent office on 2021-02-25 for superhydrophobic and self-cleaning radiative cooling film and preparation method thereof.
The applicant listed for this patent is Shaanxi University of Science & Technology. Invention is credited to Shuntian JIA, Bingying LIU, Huidi WANG, Chaohua XUE.
Application Number | 20210054185 16/679144 |
Document ID | / |
Family ID | 1000005381748 |
Filed Date | 2021-02-25 |
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United States Patent
Application |
20210054185 |
Kind Code |
A1 |
XUE; Chaohua ; et
al. |
February 25, 2021 |
SUPERHYDROPHOBIC AND SELF-CLEANING RADIATIVE COOLING FILM AND
PREPARATION METHOD THEREOF
Abstract
Disclosed are a superhydrophobic and self-cleaning radiative
cooling film and a preparation method thereof. The preparation
method includes the following steps: 1) dissolving P
(VDF.sub.x-HFP.sub.y) and PDMS in a composite polar solvent to
obtain a translucent composite polymer solution of P
(VDF.sub.x-HFP.sub.y)/PDMS; 2) adding a non-solvent dropwise to the
obtained solution to allow for a phase separation of P
(VDF.sub.x-HFP.sub.y)/PDMS to form a sol; 3) casting the sol;
drying the cast sol to obtain a film are porous inside with
micro/nano rough structures of low surface-energy on the surface.
The preparation method of the present invention is simple, and can
be used for large-scale production.
Inventors: |
XUE; Chaohua; (Xi'an,
CN) ; LIU; Bingying; (Xi'an, CN) ; WANG;
Huidi; (Xi'an, CN) ; JIA; Shuntian; (Xi'an,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Shaanxi University of Science & Technology |
Xi'an |
|
CN |
|
|
Family ID: |
1000005381748 |
Appl. No.: |
16/679144 |
Filed: |
November 8, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08J 2327/20 20130101;
C08J 5/18 20130101; C08J 2483/04 20130101; C08L 27/16 20130101;
C08L 2203/16 20130101; C08L 27/20 20130101; B29C 41/003 20130101;
C08J 2327/16 20130101; B29K 2027/12 20130101 |
International
Class: |
C08L 27/16 20060101
C08L027/16; C08L 27/20 20060101 C08L027/20; C08J 5/18 20060101
C08J005/18; B29C 41/00 20060101 B29C041/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 21, 2019 |
CN |
201910774588.9 |
Claims
1. A method for preparing a superhydrophobic and self-cleaning
radiative cooling film, comprising: 1) dissolving P
(VDF.sub.x-HFP.sub.y) and PDMS in a composite polar solvent to
obtain a translucent composite polymer solution of P
(VDF.sub.x-HFP.sub.y)/PDMS; 2) adding a non-solvent dropwise to the
obtained solution to allow for a phase separation of P
(VDF.sub.x-HFP.sub.y)/PDMS to form a sol; and 3) casting the sol;
drying the cast sol to obtain a film with a micro-nano porous
structure.
2. The method of claim 1, wherein step 1 further comprises: 101)
dissolving P (VDF.sub.x-HFP.sub.y) in an acetone solution under
stirring at room temperature for 3.about.5 h until P
(VDF.sub.x-HFP.sub.y) is completely dissolved in the acetone
solution to produce a mixture; 102) adding a prepolymer A for PDMS
and a tetrahydrofuran solvent to the resulting mixture in step 101)
and stirring uniformly; 103) adding a curing agent B under stirring
for 15-30 min until the resulting solution is uniform and
translucent.
3. The method of claim 2, wherein in step 101, a weight ratio of P
(VDF.sub.x-HFP.sub.y) to acetone is 1:(10-15).
4. The method of claim 2, wherein in step 102, a weight ratio of P
(VDF.sub.x-HFP.sub.y) to tetrahydrofuran is (1-2):15.
5. The method of claim 2, wherein in step 103, a weight ratio of P
(VDF.sub.x-HFP.sub.y) to PDMS is (2.0-4.0):1.0.
6. The method of claim 1, wherein in step 2, the non-solvent is
water, and an adding rate of the water is 0.05 mL per 10 s.
7. The method of claim 6, wherein a weight ratio of P
(VDF.sub.x-HFP.sub.y) to the water is 7:(12-6).
8. The method of claim 1, wherein in step 3, the sol is dried at
room temperature for 3-5 h.
9. A superhydrophobic and self-cleaning radiative cooling film
prepared by the method of claim 1, wherein the film with a
micro-nano porous structure has a solar reflectance of 90.1-96.5%
and a mid-infrared emissivity of 90.3-94.3%; a water contact angle
on a surface of the film is 151.4-162.3.degree.; and a water
sliding angle on the surface of the film is 1.4-8.2.degree..
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority from Chinese
Patent Application No. CN201910774588.9, filed on Aug. 21, 2019.
The content of the aforementioned application, including any
intervening amendments thereto, is incorporated herein by reference
in its entirety.
TECHNICAL FIELD
[0002] This application relates to superhydrophobic radiation
cooling materials, and more particularly to a superhydrophobic and
self-cleaning radiative cooling film and a preparation method
thereof.
BACKGROUND OF THE INVENTION
[0003] Strong solar radiation often causes sharp rising of the
temperature of ground objects in the hot summer. In recent years,
global warming causes an increase of the earth temperature and an
intensification of the urban heat island effect, so human is more
dependent on electrical air conditioners, thereby increasing the
energy consumption. Thus, it is necessary for human to find a
cooling method which is low in energy consumption or even has no
energy consumption.
[0004] Due to high solar reflectance and high mid-infrared
emissivity, the radiative cooling material emits heat to the outer
space through the transparent atmospheric window, which allows the
radiative cooling material to be an energy-saving material. Such
material can be applied on the roof or outside outdoor vehicles to
lower the temperature in the space for human activity in summer, so
that the thermal comfort of indoor environment is improved, and the
use of equipment such as air conditioners is reduced, thereby
reducing the consumption of power resources.
[0005] An existing construction film is used for cooling, which
contains nanoparticles. Such construction film has cooling effect
to some extent, but the layered coating thereof is high in cost and
complicated for operating and the influence of the environment on
cooling effect of the material is not taken into consideration. For
example, rainwater influences the service time of the material, and
the radiative cooling effect of the material is influenced when the
material is wetted by water, and dusts in the air will influence
the reflectance of the material and the mid-infrared
emissivity.
[0006] If the radiative cooling material has a superhydrophobic
property, that is, the water contact angle on a surface of the
radiative cooling material is greater than 150.degree., and water
drops slide easily on the surface of the radiative cooling
material, taking away the dirt on the radiative cooling material
during the sliding, thereby realizing self-cleaning function of the
material. The superhydrophobic property can avoid the pollution of
air pollutants and the impregnation of rainwater to the material
surface, which is beneficial to maintaining high solar reflectance
and high mid-infrared emissivity, avoiding premature degrading and
aging of the material, thus prolonging the service life.
SUMMARY OF THE INVENTION
[0007] In order to overcome the defects in the prior art, the
present invention provides a superhydrophobic and self-cleaning
radiative cooling film and a preparation method thereof. The
preparation method is simple, and can be used for large-scale
production.
[0008] The present invention adopts the following technical
solutions.
[0009] A preparation method of a superhydrophobic and self-cleaning
radiative cooling film, comprising:
[0010] 1) dissolving P (VDF.sub.x-HFP.sub.y) and PDMS in a
composite polar solvent to obtain a translucent composite polymer
solution of P (VDF.sub.x-HFP.sub.y)/PDMS;
[0011] 2) adding a non-solvent dropwise to the obtained solution to
allow for a phase separation of P (VDF.sub.x-HFP.sub.y)/PDMS to
form a sol; and
[0012] 3) casting the sol; drying the cast sol to obtain a film
with a micro-nano porous structure.
[0013] Specifically, step 1 further comprises the following
steps.
[0014] 101) dissolving P (VDF.sub.x-HFP.sub.y) in an acetone
solution under stirring at room temperature for 3.about.5 h until P
(VDF.sub.x-HFP.sub.y) is completely dissolved in the acetone
solution to produce a mixture;
[0015] 102) adding a prepolymer A for PDMS and a tetrahydrofuran
solvent to the resulting mixture in step 101 and stirring
uniformly;
[0016] 103) adding a curing agent B for PDMS under stirring for
15-30 min until the resulting solution is even and translucent.
[0017] Further, in step 101, a weight ratio of P
(VDF.sub.x-HFP.sub.y) to acetone is 1:(10-15).
[0018] Further, in step 102, a weight ratio of P
(VDF.sub.x-HFP.sub.y) to tetrahydrofuran is (1-2):15.
[0019] Further, in step 103, a weight ratio of P
(VDF.sub.x-HFP.sub.y) to PDMS is (2.0-4.0):1.0.
[0020] Specifically, in step 2, the non-solvent is water, and an
adding rate of the water is 0.05 mL per 10 s.
[0021] Further, a weight ratio of P (VDF.sub.x-HFP.sub.y) to the
water is 7:(12-6).
[0022] Further, the sol is dried at room temperature for 3-5 h.
[0023] In a second aspect, the present invention provides a
superhydrophobic and self-cleaning radiative cooling film. The film
with a micro-nano porous structure has a solar reflectance of
90.1-96.5% and a mid-infrared emissivity of 90.3-94.3%; a water
contact angle on a surface of the film is 151.4-162.3.degree.; and
a water sliding angle on the surface of the film is
1.4-8.2.degree..
[0024] Compared with the prior art, the present invention has the
following beneficial effects.
[0025] In the preparation method of the present invention, the
composite polymer of P (VDF.sub.x-HFP.sub.y)/PDMS is induced for a
phase separation by water, and a superhydrophobic radiative cooling
film with a micro-nano porous structure is directly obtained when
the material is formed. All operations are carried out under room
temperature, so mild conditions are required in this method. During
the preparation of the film, materials can obtain higher solar
reflectance and higher mid-infrared emissivity without adding mirco
or nano-sized particles, and surfaces of the material are not
needed to be plated with metal films.
[0026] Further, a dense layer is formed when only the P
(VDF.sub.x-HFP.sub.y) is cast at room temperature, but such dense
layer will be changed in the present invention due to the addition
of polydimethylsiloxane. The micro-roughness required to achieve
superhydrophobicity is formed during the formation of the porous
structure due to the mass transfer diffusion process in which the
two mixed polymers compete in the solvent, and different
volatilization mechanisms of the two-component mixed solvent. Such
rough network structure may contribute to develop healthy and
environmentally friendly particle-free scattering media. Moreover,
P (VDF.sub.x-HFP.sub.y) and PDMS have low-energy surfaces and have
good chemical stability. The microstructure formed by the phase
separation has excellent superhydrophobicity, which ensures that
the passive radiative cooling film will have good weather
resistance and a long service life.
[0027] Further, the weight ratio of P (VDF.sub.x-HFP.sub.y) to
acetone is 1:(10-15), which allows the polymer to be fully
dissolved, so that the solution is avoided to be too viscous to
have poor fluidity, and the waste of excess solvents is reduced.
The weight ratio of P (VDF.sub.x-HFP.sub.y) to PDMS was
(2.0.about.4.0):1.0. It was found that when the two polymers had
different ratios, different microscopic morphologies appeared, but
the superhydrophobic and self-cleaning radiation cooling effect
could be achieved with all ratios. The weight ratio of P
(VDF.sub.x-HFP.sub.y) to tetrahydrofuran is (1.about.2):15, which
allows PDMS to well disperse in the resulting solution. Moreover,
the boiling point of tetrahydrofuran is between that of acetone and
that of water, which provides a certain synergistic effect during
the evaporation of the solvent to further convert the sol into a
porous structure.
[0028] Further, in the present invention, water is used as a
non-solvent to induce the phase separation, so that the porogen
used in the conventional operation is avoided, which is non-toxic
and environmentally friendly.
[0029] Further, in the present invention, the porous radiative
cooling film with superhydrophobic and self-cleaning properties is
obtained by drying at normal temperature, so complicated equipment
and excess energy consumption are omitted, which can be used for
large-scale industrial production.
[0030] The superhydrophobic and self-cleaning radiative cooling
film has high solar reflectance, high mid-infrared emissivity and
superhydrophobic property, so this material has strong radiative
cooling effect and excellent antifouling and self-cleaning
performance.
[0031] In summary, the present invention has a simple preparation
method and can realize a large-area production.
[0032] Technical solutions of the present invention will be further
described in detail below with reference to the accompanying
drawings and embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1 is an image showing a morphology and a water contact
angle on a surface of a superhydrophobic and self-cleaning
radiative cooling film obtained in Example 2 of the present
invention.
[0034] FIG. 2 is a picture of the superhydrophobic and
self-cleaning cooling film obtained in Example 2 of the present
invention, showing the state of colored water drops on the
film.
[0035] FIG. 3 is an image showing a self-cleaning effect of the
superhydrophobic and self-cleaning radiative cooling film obtained
in Example 2 of the present invention.
[0036] FIG. 4 is an image showing thermal infrared imaging of the
superhydrophobic and self-cleaning radiative cooling film under a
solar irradiation environment obtained in Example 6 of the present
invention.
DETAILED DESCRIPTION OF EMBODIMENTS
[0037] In this invention, provided are a superhydrophobic and
self-cleaning radiative cooling film and a preparation method
thereof. The preparation method comprises the following steps. Poly
(vinylidene fluoride-co-hexafluoropropylene) P
(VDF.sub.x-HFP.sub.y) and polydimethylsiloxane (PDMS) are dissolved
in a composite polar solvent to obtain a translucent composite
polymer solution of P (VDF.sub.x-HFP.sub.y)/PDMS. Then, the
non-solvent water is added dropwise to the solution to allow for a
phase separation of P (VDF.sub.x-HFP.sub.y)/PDMS to obtain a sol.
Finally, the sol is cast and dried to obtain a film having a
micro-nano porous structure. The prepared film material has a solar
reflectance of 96.5% and a mid-infrared emissivity of 94.3%, and
the heat is emitted by infrared radiation through a transparent
atmospheric window (8.about.13 .mu.m), thereby lowering the
temperature of the object on the lower surface of the film by
5.about.8.degree. C., achieving good cooling effect. A water
contact angle on a surface of the material is 162.3.degree. and a
water sliding angle of on the surface of the material is at least
1.4.degree., which has good antifouling and self-cleaning
properties.
[0038] The present invention provides a method for preparing a
superhydrophobic and self-cleaning radiative cooling film,
comprising the following steps.
[0039] 1) P (VDF.sub.x-HFP.sub.y) and PDMS are dissolved in a
composite polar solvent to obtain a translucent composite polymer
solution of P (VDF.sub.x-HFP.sub.y)/PDMS.
[0040] Specifically, step 1 further comprises the following
steps.
[0041] 101) P (VDF.sub.x-HFP.sub.y) is dissolved in an acetone
solution under stirring at room temperature for 3.about.5 h until P
(VDF.sub.x-HFP.sub.y) is completely dissolved in the acetone
solution to produce a mixture, where a weight ratio of P
(VDF.sub.x-HFP.sub.y) to acetone is 1:(10-15).
[0042] 102) A prepolymer A for PDMS is added into the mixture, and
then a tetrahydrofuran solvent is added into the added mixture and
stirring uniformly, where a weight ratio of P (VDF.sub.x-HFP.sub.y)
to tetrahydrofuran is (1-2):15.
[0043] 103) a curing agent B is added under stirring for 15-30 min
until the resulting solution is uniform and translucent, where a
weight ratio of P (VDF.sub.x-HFP.sub.y) to PDMS is
(2.0-4.0):1.0.
[0044] 2) A non-solvent is dropwise added to the obtained solution
to allow for a phase separation of P (VDF.sub.x-HFP.sub.y)/PDMS to
form a sol; where the non-solvent is water, and an adding rate of
the water is 0.05 mL per 10 s. A weight ratio of P
(VDF.sub.x-HFP.sub.y) to the water is 7:(12-6).
[0045] 3) The sol is cast, and the cast sol is dried to obtain a
film with a micro-nano porous structure.
[0046] The obtained sol is poured into an open container or a
surface of a substrate, and is dried at room temperature for 3-5 h
to obtain a film having a micro-nano porous structure.
[0047] The superhydrophobic and self-cleaning radiative cooling
film of the present invention has a solar reflectance of 90.1-96.5%
and a mid-infrared emissivity of 90.3-94.3%; a water contact angle
on a surface of the film is 151.4-162.3.degree.; and a water
sliding angle on the surface of the film is 1.4-8.2.degree..
[0048] The present invention will be clearly and completely
described in conjunction with the accompanying drawings and
embodiments, from which the purposes, technical solutions and
advantages of the present invention will be much clearer.
Obviously, the described embodiments are only a part of the
embodiments of the present invention. The description of drawings
and the components of the embodiments of the invention may be
arranged and designed in various configurations. Therefore, the
detailed description of the embodiments herein are only a part of
the embodiments of the present invention and are not intended to
limit the scope of the present invention. Any other embodiments
made by the ordinary skilled in the prior art without paying
creative efforts based on the embodiments of the present invention
shall fall within the scope of the present invention.
Example 1
[0049] In this embodiment, illustrated are a superhydrophobic and
self-cleaning radiative cooling film and a preparation method
thereof. The preparation method comprises the following steps.
[0050] Step 1
[0051] 3.5 g of P (VDF.sub.x-HFP.sub.y) was dissolved in 49 g of
the acetone solution under stirring at room temperature for 3 h
until P (VDF.sub.x-HFP.sub.y) is completely dissolved in the
acetone solution to produce a mixture, and then 1 g of the
prepolymer A for PDMS and 30 g of tetrahydrofuran were added in
sequence, and the mixture was stirred uniformly, and then 0.1 g of
a curing agent B was added into the mixture, and the resulting
solution was uniformly stirred for 15 min to obtain a translucent
solution.
[0052] Step 2
[0053] 3.0 g of water was added dropwise to the translucent
solution at a rate of 0.05 mL per 10 s under stirring to form a
sol.
[0054] Step 3
[0055] The obtained sol was poured into a Petri dish of 90 mm and
dried at room temperature for 3 h until the solvent and water were
completely evaporated, and then a microporous radiative cooling
film with superhydrophobic and self-cleaning properties was
obtained.
[0056] The radiative cooling film of this embodiment has a solar
reflectance of 94.2% and a mid-infrared emissivity of 93.5%; a
water contact angle on a surface of the film is
153.0.+-.0.8.degree.; and a water sliding angle on a surface of the
film is 6.1.+-.0.5.degree..
Example 2
[0057] In this embodiment, illustrated are a superhydrophobic and
self-cleaning radiative cooling film and a preparation method
thereof. The preparation method comprises the following steps.
[0058] Step 1
[0059] 3.5 g of P (VDF.sub.x-HFP.sub.y) was dissolved in 42 g of
the acetone solution under stirring at room temperature for 3.5 h
until P (VDF.sub.x-HFP.sub.y) is completely dissolved in the
acetone solution to form a mixture, and then 1 g of prepolymer A
for PDMS and 30 g of the tetrahydrofuran solvent were added into
the mixture in sequence, and the mixture was stirred uniformly, and
then 0.1 g of a curing agent B was added, and the resulting
solution was evenly stirred for 30 min to obtain a translucent
solution.
[0060] Step 2
[0061] 5.0 g of water was added dropwise to the translucent
solution at a rate of 0.05 mL per 10 s under stirring to form a
sol.
[0062] Step 3
[0063] The obtained sol was poured into a Petri dish of 90 mm and
dried at room temperature for 4 h until the solvent and water were
completely evaporated, and then a microporous radiative cooling
film with superhydrophobic and self-cleaning properties was
obtained.
[0064] The radiative cooling film of this embodiment has a solar
reflectance of 96.5% and a mid-infrared emissivity of 94.3%; a
water contact angle on a surface of the film is
158.0.+-.1.7.degree.; and a water sliding angle on a surface of the
film is 3.0.+-.0.5.degree..
Example 3
[0065] In this embodiment, illustrated are a superhydrophobic and
self-cleaning radiative cooling film and a preparation method
thereof. The preparation method comprises the following steps.
[0066] Step 1
[0067] 3.0 g of P (VDF.sub.x-HFP.sub.y) was dissolved in 36 g of
the acetone solution under stirring at room temperature for 5 h
until P (VDF.sub.x-HFP.sub.y) was completely dissolved in the
acetone solution to form a mixture, and then 1 g of prepolymer A
for PDMS and 30 g of the tetrahydrofuran solvent were added into
the mixture in sequence, and then the mixture was stirred
uniformly, and then 0.1 g of a curing agent B was added into the
mixture, and the resulting solution was evenly stirred for 20 min
to obtain a translucent solution.
[0068] Step 2
[0069] 3.4 g of water was added dropwise to the translucent
solution at a rate of 0.05 mL per 10 s under stirring to form a
sol.
[0070] Step 3
[0071] The obtained sol was poured into a Petri dish of 90 mm and
dried at room temperature for 5 h until the solvent and water were
completely evaporated, and then a microporous radiative cooling
film with superhydrophobic and self-cleaning properties was
obtained.
[0072] The radiative cooling film of this embodiment has a solar
reflectance of 95.7% and a mid-infrared emissivity of 93.4%; a
water contact angle on a surface of the film is
156.0.+-.1.3.degree.; and a water sliding angle on a surface of the
film is 5.3.+-.0.8.degree..
Example 4
[0073] In this embodiment, illustrated are a superhydrophobic and
self-cleaning radiative cooling film and a preparation method
thereof. The preparation method comprises the following steps.
[0074] Step 1
[0075] 4.0 g of P (VDF.sub.x-HFP.sub.y) was dissolved in 48 g of
the acetone solution under stirring at room temperature for 3.5 h
until P (VDF.sub.x-HFP.sub.y) was completely dissolved in the
acetone solution to form a mixture, and then 1 g of a prepolymer A
for PDMS and 30 g of the tetrahydrofuran solvent were added in
sequence into the mixture, and then the mixture was stirred
uniformly, and then 0.1 g of a curing agent B was added into the
mixture, and the resulting solution was uniformly stirred for 25
min to obtain a translucent solution.
[0076] Step 2
[0077] 5.7 g of water was added dropwise to the translucent
solution at a rate of 0.05 mL per 10 s under stirring to form a
sol.
[0078] Step 3
[0079] The obtained sol was poured into a Petri dish of 90 mm and
dried at room temperature for 3 h until the solvent and water were
completely evaporated, and then a microporous radiative cooling
film with superhydrophobic and self-cleaning properties was
obtained.
[0080] The radiative cooling film of this embodiment has a solar
reflectance of 93.6% and a mid-infrared emissivity of 94.1%; a
water contact angle on a surface of the film is
162.3.+-.1.0.degree.; and a water sliding angle on a surface of the
film is 2.0.+-.0.6.degree..
Example 5
[0081] In this embodiment, illustrated are a superhydrophobic and
self-cleaning radiative cooling film and a preparation method
thereof. The preparation method comprises the following steps.
[0082] Step 1
[0083] 3.5 g of P (VDF.sub.x-HFP.sub.y) was dissolved in 42 g of
the acetone solution under stirring at room temperature for 3 h
until P (VDF.sub.x-HFP.sub.y) was completely dissolved in the
acetone solution to form a mixture, and then 1 g of the prepolymer
A for PDMS and 30 g of the tetrahydrofuran solvent were added in
sequence into the mixture, and the mixture was stirred uniformly,
and then 0.1 g of a curing agent B was added into the mixture, and
the resulting solution was uniformly stirred for 15 min to obtain a
translucent solution.
[0084] Step 2
[0085] 4.0 g of water was added dropwise to the translucent
solution at a rate of 0.05 ml per 10 s under stirring to form a
sol.
[0086] Step 3
[0087] The obtained sol was poured into a Petri dish of 90 mm and
dried at room temperature for 4 h until the solvent and water were
completely evaporated, and then a microporous radiative cooling
film with superhydrophobic and self-cleaning properties was
obtained.
[0088] The radiative cooling film of this embodiment has a solar
reflectance of 95.6% and a mid-infrared emissivity of 93.8%; a
water contact angle on a surface of the film is
157.3.+-.0.6.degree.; and a water sliding angle on a surface of the
film is 4.9.+-.0.3.degree..
Example 6
[0089] In this embodiment, illustrated are a superhydrophobic and
self-cleaning radiative cooling film and a preparation method
thereof. The preparation method comprises the following steps.
[0090] Step 1
[0091] 3.5 g of P (VDF.sub.x-HFP.sub.y) was dissolved in 49 g of
the acetone solution under stirring at room temperature for 3.5 h
until P (VDF.sub.x-HFP.sub.y) was completely dissolved in the
acetone solution to form a mixture, and then 1 g of the prepolymer
A for PDMS and 30 g of the tetrahydrofuran solvent were added in
sequence into the mixture, and the mixture was stirred uniformly,
and then 0.1 g of the curing agent B was added into the mixture,
and the resulting solution was uniformly stirred for 30 min to
obtain a translucent solution.
[0092] Step 2
[0093] 6.0 g of water was added dropwise to the translucent
solution at a rate of 0.05 ml per 10 s under stirring to form a
sol.
[0094] Step 3
[0095] The obtained sol was poured into a Petri dish of 90 mm and
dried at room temperature for 3 h until the solvent and water were
completely evaporated, and then a microporous radiative cooling
film with superhydrophobic and self-cleaning properties was
obtained.
[0096] The radiative cooling film of this embodiment has a solar
reflectance of 95.2% and a mid-infrared emissivity of 93.6%; a
water contact angle on a surface of the film is
156.2.+-.0.6.degree.; and a water sliding angle on a surface of the
film is 4.2.+-.0.5.degree..
Example 7
[0097] In this embodiment, illustrated are a superhydrophobic and
self-cleaning radiative cooling film and a preparation method
thereof. The preparation method comprises the following steps.
[0098] Step 1
[0099] 2.0 g of P (VDF.sub.x-HFP.sub.y) was dissolved in 28 g of
the acetone solution under stirring at room temperature for 3 h
until P (VDF.sub.x-HFP.sub.y) was completely dissolved in the
acetone solution to form a mixture, and then 1 g of a prepolymer A
for PDMS and 30 g of the tetrahydrofuran solvent were added in
sequence into the mixture, and the mixture was stirred uniformly,
and then 0.1 g of a curing agent B was added into the mixture, and
the resulting solution was uniformly stirred for 20 min to obtain a
translucent solution.
[0100] Step 2
[0101] 2.9 g of water was added dropwise to the translucent
solution at a rate of 0.05 ml per 10 s under stirring to form a
sol.
[0102] Step 3
[0103] The obtained sol was poured into a Petri dish of 90 mm and
dried at room temperature for 4 h until the solvent and water were
completely evaporated, and then a microporous radiative cooling
film with superhydrophobic and self-cleaning properties was
obtained.
[0104] The radiative cooling film of this embodiment has a solar
reflectance of 90.1% and a mid-infrared emissivity of 93.2%; a
water contact angle on a surface of the film is
151.4.+-.0.5.degree.; and a water sliding angle on a surface of the
film is 8.2.+-.0.7.degree..
Comparative Example 1
[0105] Step 1
[0106] 3.5 g of P (VDF.sub.x-HFP.sub.y) was dissolved in 42 g of
the acetone solution under stirring at room temperature for 3 h
until P (VDF.sub.x-HFP.sub.y) was completely dissolved in the
acetone solution.
[0107] Step 2
[0108] The obtained solution was poured into a Petri dish of 90 mm
and dried at room temperature for 2 h until the solvent and water
were completely evaporated, and then an optically transparent
plastic film was obtained.
[0109] The optically transparent plastic film has a solar
reflectance of 8.3% and a mid-infrared emissivity of 92.5%; a water
contact angle on a surface of the optically transparent plastic
film is 92.3.+-.0.2.degree.; and a water sliding angle on the
surface of the optically transparent plastic film is 0.degree..
Comparative Example 2
[0110] Step 1
[0111] 3.5 g of P (VDF.sub.x-HFP.sub.y) was dissolved in 42 g of
the acetone solution under stirring at room temperature for 3 h
until P (VDF.sub.x-HFP.sub.y) was completely dissolved in the
acetone solution.
[0112] Step 2
[0113] 4.0 g of water was added dropwise to the translucent
solution at a rate of 0.05 ml per 10 s under stirring to form a
sol.
[0114] Step 3
[0115] The obtained sol was poured into a Petri dish of 90 mm and
dried at room temperature for 3 h until the solvent were completely
evaporated, and then a porous film was obtained.
[0116] The porous film has a solar reflectance of 87.9% and a
mid-infrared emissivity of 92.9%; a water contact angle on a
surface of the porous film is 118.2.+-.0.4.degree.; and a water
sliding angle on the surface of the porous film is 0.degree..
[0117] The test items involved in the present invention are the
reflectance R, the infrared radiance E, the contact angle CA, and
the sliding angle SA.
[0118] The test results are shown in the following table:
TABLE-US-00001 TABLE 1 Test results of Examples and Comparative
Examples Compar- Compar- ative ative Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5
Ex. 6 Ex. 7 Ex. 1 Ex. 2 R 94.2 96.5 95.7 93.6 95.6 95.2 90.1 8.3
87.9 (%) E 93.5 94.3 93.4 94.1 93.8 93.6 93.2 92.5 92.9 (%) CA
153.0 .+-. 0.8 158.0 .+-. 1.7 156.0 .+-. 1.3 162.3 .+-. 1.0 157.0
.+-. 0.6 156.2 .+-. 0.6 151.4 .+-. 0.5 92.3 .+-. 0.2 118.2 .+-. 0.4
(.degree.) SA 6.1 .+-. 0.5 3.0 .+-. 0.5 5.3 .+-. 0.8 2.0 .+-. 0.6
4.9 .+-. 0.3 4.2 .+-. 0.5 8.2 .+-. 0.7 -- -- (.degree.)
[0119] In the embodiments of the present invention, P
(VDF.sub.x-HFP.sub.y) and PDMS were dissolved in a composite polar
solvent of acetone and tetrahydrofuran, and were induced for the
phase separation. In Comparative Example 1, only P
(VDF.sub.x-HFP.sub.y) was dissolved in acetone, and no water was
added. The solar reflectance of the superhydrophobic and
self-cleaning radiation cooling material prepared in the
embodiments of the present invention is about 12 times of that of
Comparative Example 1, and has excellent self-cleaning performance
compared with Comparative Example 1. In Comparative Example 2, only
P (VDF.sub.x-HFP.sub.y) was dissolved in acetone, and the water was
added. The solar reflectance of the superhydrophobic and
self-cleaning radiation cooling material prepared in the
embodiments of the present invention is significantly higher than
that of Comparative Example 2. Moreover, in the present invention,
the contact angle is increased to 150.degree. or more, and the
sliding angle is close to 0.degree., and the surface formed in
Comparative Example 2 enables water to slide thereon, and the
surface dirt cannot be taken away.
[0120] Referring to FIG. 1, the surface of the superhydrophobic and
self-cleaning radiative cooling film obtained in Example 2 of the
present invention has a micro-nano porous structure, and a
micro-nano roughness is accordingly formed due to the porous
structure, and the water contact angle is up to 158.degree..
[0121] Referring to FIG. 2, the superhydrophobic and self-cleaning
radiative cooling film obtained in Example 2 is white matt, and
water drops stand on the surface thereof in a spherical shape.
[0122] Referring to FIG. 3, the superhydrophobic and self-cleaning
radiative cooling film obtained in Example 2 of the present
invention has an excellent self-cleaning effect, and water drops
can remove the dirt on the film when passing through a place with
dirt, thereby achieving a self-cleaning effect.
[0123] Referring to FIG. 4, the superhydrophobic and self-cleaning
radiative cooling film obtained in Example 6 is placed in the
practical environment (tested in Shaanxi University of Science
&Technology, Xi'an, Shaanxi, China, on Aug. 14, 2019, 3:50 pm;
outdoor temperature: about 40.degree. C.). The infrared camera
observed that all objects on the ground are heated to above
50.degree. C. by the sun, and surface temperature thereof are kept
at about 40.degree. C. by using the prepared film of the present
invention without isolating heat convection and heat conduction.
This proved that the film prepared in the invention has a good
radiation self-cooling effect.
[0124] As can be seen from Table 1, in the present invention, P
(VDF.sub.x-HFP.sub.y) and PDMS are induced for the phase separation
in the composite solvent and water to form a micro-nano porous
structure, and a micro-nano roughness is formed on the surface. The
P (VDF.sub.x-HFP.sub.y) and PDMS cooperate with each other to have
high solar reflectance and self-cleaning performance. The present
invention is simple in operating, and is suitable for the
large-scale production, and can be applied on surfaces of objects
with various shapes, such as buildings, vehicles, outdoor products,
and low-temperature storage facilities. The present invention has a
broad application prospect and is important to save power resources
and reduce energy consumption to slow down the global warming
trend.
[0125] The above description is only for illustration, and is not
intended to limit the scope of the present invention. Any
modifications made on the basis of technical solutions of the
present invention shall fall within the scope of the present
invention.
* * * * *