NL2030644B1

NL2030644B1 - Mechanically durable superhydrophobic nano-coating and preparation method thereof

Info

Publication number: NL2030644B1
Application number: NL2030644A
Authority: NL
Inventors: Yang Jinshui; Yin Changping; Peng Chaoyi; Xing Suli; Wu Binrui; Wu Nan; Jiang Dazhi; Ju Su
Original assignee: National Univ Of Defense Technology
Priority date: 2022-01-21
Filing date: 2022-01-21
Publication date: 2023-08-01

Abstract

U I T T R E K S E L The present invention discloses a mechanically durable superhydrophobic nano—coating and a preparation method thereof. The nano—coating provided in the present invention has excellent mechanical durability and high practical values. 5 (+ Fig.)

Description

P923/NLpd

MECHANICALLY DURABLE SUPERHYDROPHOBIC NANO-COATING AND PREPARATION

METHOD THEREOF

TECHNICAL FIELD

The present invention relates to the technical field of prep- aration of coatings, and in particular to a mechanically durable superhydrophobic nano-coating and a preparation method thereof.

BACKGROUND ART

At present, most of superhydrophobic materials have the same problem of poor durability, especially mechanical durability, mainly because a superhydrophobic surface can be achieved through a micro-nano secondary structure, and the strength of such a fine structure is usually low.

SUMMARY

The present invention provides a mechanically durable super- hydrophobic nano-coating using a nanofiber membrane as a skeletal reinforcement phase and a resin slurry as a matrix phase; the nanofiber membrane has an average thickness of 10-30 pm, preferably 10-20 um; and the fiber has an average diameter of 200- 600 nm, preferably 200-500 nm. the resin slurry comprises a resin slurry I and a resin slur- ry II; the resin slurry I is a mixture of a hydrophobically modi- fied epoxy resin, nanoparticles and a curing agent; and the resin slurry II is a mixture of a hydrophobically modified epoxy resin and a curing agent; the nanofiber membrane is one of polyvinylidene fluoride fi- ber membrane, polyacrylonitrile fiber membrane, polystyrene fiber membrane, silicon-carbon oxide fiber membrane, silicon carbide fi- ber membrane, alumina fiber membrane and zirconia fiber membrane.

To achieve the above purpose, the present invention further provides a preparation method of a mechanically durable superhy- drophobic nano-ccating, including the following steps: (1) adding a mixture of a hydrophobically modified epoxy res- in, nanoparticles and a curing agent to a diluent, and mixing the nanoparticles, the curing agent and the hydrophobically modified epoxy resin well by ultrasonic emulsification and high-speed shearing to obtain a resin slurry I; adding a hydrophobically modified epoxy resin and a curing agent to a diluent, stirring and mixing well to obtain a resin slurry II; the hydrophobically modified epoxy resin is one of hydropho- bically modified E-51 epoxy resin, E-44 epoxy resin and E-42 epoxy resin; the nanoparticles are one of silica nanoparticles, titanium dioxide nanoparticles and aluminum oxide nanoparticles; the curing agent is at least one of diethylenetriamine, diaminodiphenylme- thane, polyether amine D-230 and polyether amine D-400; and the diluent is at least one of ethyl acetate, ethanol, N.N- dimethylformamide, dimethyl sulfoxide, cyclohexane and acetone.

In the resin slurry I, the mass ratio of the hydrophobically modified epoxy resin to the nanoparticles is (1.5-3):1; and the mass ratio of the diluent to the total mass of the hydrophobically modified epoxy resin, the nanoparticles and the curing agent is (3-5) :1.

In the resin slurry II, the mass ratio of the diluent to the total mass of the hydrophobically modified epoxy resin and the curing agent is (0.5-1.5):1. The nanoparticles have an average particle size of 20-50 nm. (2) coating the resin slurry II on a substrate and curing at 80 °C for 10-40 min; impregnating the nanofiber membrane in the resin slurry I, then volatilizing to remove the diluent in the resin slurry I in the nanofiber membrane, and repeating the above impregnation and volatilization processes for several times; and

The amount of the resin slurry II coated on the substrate is 0.003-0.014 g/cm’, preferably 0.005-0.012 g/cm’.

Impregnation is performed at 20-30 °C for 3-5 min, and volat- ilization is natural volatilization at room temperature; the im- pregnation and volatilization processes are repeated for 3-8 times, preferably 3-5 times, to allow the nanoparticles and the hydrophobic resin to fully penetrate into the nanofiber membrane. {3) superposing the impregnated nanofiber membrane on the substrate coated with the resin slurry II, heating and curing to obtain a mechanically durable superhydrophobic nano-coating.

The heating and curing process is carried out at 70-85 °C for 1-2 h in the first stage, and at 90-100 °C for 1-2 h in the second stage.

The present invention has the following beneficial effects:

According to the mechanically durable superhydrophobic nano- coating provided in the present invention, a micro-nano secondary structure is co-constructed from micron-sized pores between nano- fibers and the nanoparticles, and low surface energy is enabled on surfaces of the nanofiber membrane and the nanoparticles by the hydrophobic epoxy resin, so that the surfaces have superhydropho- bicity. In addition, a multi-phase reinforced nanocomposite with a structure similar to that of “reinforced concrete” formed by com- bination of the nanofiber membrane, the hydrophobic epoxy resin and the nanoparticles has excellent mechanical durability, so that the superhydrophobic nano-coating has high practical values.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. la is a picture of surface micromorphology of a superhy- drophobic coating obtained in Embodiment 1;

FIG. 1b is a picture of surface hydrophobicity of the super- hydrophobic coating obtained in Embodiment 1;

FIG. 2a is a picture of surface micromorphology of the super- hydrophobic coating obtained in Embodiment 1 after being sanded with a 600-mesh sandpaper for 60 times;

FIG. 2b is a picture of hydrophobicity of the superhydropho- bic coating obtained in Embodiment 1 after being sanded with a 600-mesh sandpaper for 60 times;

FIG. 3 shows morphology of silicon carbide fiber used in Em- bodiment 3;

FIG. da is a picture of surface micromorphology of the super- hydrophobic coating obtained in Embodiment 3 after being sanded with a 600-mesh sandpaper for 60 times;

FIG. 4b is a picture of hydrophobicity of the superhydropho- bic coating obtained in Embodiment 3 after being sanded with a 600-mesh sandpaper for 60 times;

FIG. 5a is a picture of surface micromorphology of a coating in Comparative Example 1 after stripping with a tape for 5 times;

FIG. 5b is a picture of hydrophobicity of a coating in Com- parative Example 1 after stripping with a tape for 5 times;

FIG. 6a is an optical picture showing interior of a coating in Comparative Example 2; and

FIG. éb is a picture of surface micromorphology of a coating in Comparative Example 2.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiment 1

The embodiment provides a mechanically durable superhydropho- bic nano-coating with a coating thickness of about 0.4 mm; the nano-coating uses a polyacrylonitrile fiber membrane as a skeletal reinforcement phase, with an average fiber diameter of 200 nm and an average fiber membrane thickness of 12 um, and uses a resin slurry as a matrix phase; the resin slurry includes a resin slurry

I and a resin slurry II; the resin slurry I is a mixture of hydro- phobically modified E-51 epoxy resin, aluminum oxide nanoparticles and polyether amine D-230; and the resin slurry II is a mixture of hydrophobically modified E-51 epoxy resin and polyether amine D- 230.

The embodiment further provides a preparation method of a me- chanically durable superhydrophobic nano-coating, including: (1) adding a mixture of 10 g of hydrophobically modified E-51 epoxy resin, 5 g of aluminium oxide nanoparticles and 3 g of poly- ether amine D-230 to 75 g of ethyl acetate diluent, and mixing the aluminium oxide nanoparticles, the polyether amine D-230 and the hydrophobically modified E-51 epoxy resin well by ultrasonic emul- sification and high-speed shearing to obtain a resin slurry I; adding 5 g of hydrophobically modified E-51 epoxy resin and 1.5 g of polyether amine D-230 to 5 g of ethyl acetate diluent, stirring and mixing well to obtain a resin slurry II; {2} coating the resin slurry II on a substrate with a coating surface density of 0.005 g/cm”, and curing at 80 °C for 20 min; impregnating the polyacrylonitrile fiber membrane in the res- in slurry I, then volatilizing to remove the ethyl acetate in the resin slurry I in the polyacrylonitrile fiber membrane, and re-

peating the above impregnation and volatilization processes for 3 times; and (3) superposing the impregnated polyacrylonitrile fiber mem- brane on the substrate coated with the resin slurry II, heating 5 and curing at 80 °C for 1 h and 100 °C for 1 h to obtain a mechan- ically durable superhydrophobic nano-coating.

The superhydrophobic nano-coating has uniform nanoparticles on the surface, with a water contact angle of 156.8° as shown in

FIG. la; after sanding with a 600-mesh sandpaper for 60 times, the contact angle decreases to 147.4°, a nanofiber skeleton, nanopar- ticles and resins are exposed on the surface to construct a new micro-nano structure, as shown in FIG. 2a; after sanding with a 360-mesh sandpaper for 90 times, the contact angle deceases to 146.6°; and after 50 times of gravel impact tests, the contact an- gle of the superhydrophobic composite decreases to 142.2°. The pictures of hydrophobicity in FIG. 1b and FIG. 2b show that the superhydrophobic nano-coating provided in the embodiment has high hydrophobicity. The results show that the superhydrophobic nano- coating with a polyacrylonitrile nanofiber membrane as a skeleton can keep superhydrophobicity under friction and dynamic impact, indicating that the superhydrophobic nano-composite has good me- chanical durability.

Embodiment 2

The embodiment provides a mechanically durable superhydropho- bic nano-coating with a coating thickness of about 0.4 mm; the nano-coating uses a polyvinylidene fluoride fiber membrane as a skeleton, with an average fiber diameter of 400 nm and an average fiber membrane thickness of 25 um, and uses a resin slurry as a matrix phase; the resin slurry includes a resin slurry I and a resin slurry II; the resin slurry I is a mixture of hydrophobical- ly modified E-51 epoxy resin, titanium dioxide nanoparticles and diethylenetriamine; and the resin slurry II is a mixture of hydro- phobically modified E-51 epoxy resin and diethylenetriamine.

The embodiment further provides a preparation method of a me- chanically durable superhydrophobic nano-coating, including: (1) adding a mixture of 10 g of hydrophobically modified E-51 epoxy resin, 4 g of titanium dioxide nanoparticles and 3 g of di-

ethylenetriamine to 75 g of cyclohexane diluent, and mixing the titanium dioxide nanoparticles, the diethylenetriamine and the hy- drophobically modified E-51 epoxy resin well by ultrasonic emulsi- fication and high-speed shearing to obtain a resin slurry I; adding 5 g of hydrophobically modified E-51 epoxy resin and 1.5 g of diethylenetriamine to 5 g of cyclohexane diluent, stir- ring and mixing well to obtain a resin slurry II; (2) coating the resin slurry II on a substrate with a coating surface density of 0.0lg/cm®, and curing at 90°C for 15min; impregnating the polyvinylidene fluoride fiber membrane in the resin slurry I, then volatilizing to remove the cyclohexane in the resin slurry I in the polyvinylidene fluoride fiber membrane, and repeating the above impregnation and volatilization processes for 5 times; and (3) superposing the impregnated polyvinylidene fluoride fiber membrane on the substrate coated with the resin slurry II, heating and curing at 75 °C for 1.5 h and 100 °C for 1 h to obtain a me- chanically durable superhydrophobic nano-coating.

The superhydrophobic nano-coating has uniform nanoparticles on the surface, with an average water contact angle of 155.2%; af- ter sanding with a 600-mesh sandpaper for 60 times, the contact angle decreases to 150.3°, a nanofiber skeleton, nanoparticles and resins are exposed on the surface; after sanding with a 360-mesh sandpaper for 100 times, the surface water contact angle deceases to 148.6°; after adhesion with 3M tape for 10 times, the surface water contact angle is 147.6°; and after 50 times of gravel impact tests, the contact angle of the superhydrophobic composite is 148.2°. The results show that the superhydrophobic nano-coating with a polyvinylidene fluoride nanofiber membrane as a skeleton can keep superhydrophobicity under friction and dynamic impact, indicating that the superhydrophobic nano-composite has good dura- bility.

Embodiment 3

The embodiment provides a mechanically durable superhydropho- bic nano-coating with a coating thickness of about 0.4 mm; the nano-coating uses a silicon carbide fiber membrane as a skeleton,

with an average fiber diameter of 500 nm and an average fiber mem- brane thickness of 20 pm, with fiber morphology as shown in FIG.3; and uses a resin slurry as a matrix phase; the resin slurry in- cludes a resin slurry I and a resin slurry II; the resin slurry IT is a mixture of hydrophobically modified E-42 epoxy resin, silica nanoparticles and polyether amine D-400; and the resin slurry II is a mixture of hydrophobically modified E-42 epoxy resin and pol- yether amine D-400.

The embodiment further provides a preparation method of a me- chanically durable superhydrophobic nano-coating, including: (1) adding a mixture of 10 g of hydrophobically modified E-42 epoxy resin, 3.5 g of silica nanoparticles and 3 g of polyether amine D-400 to 75 g of acetone diluent, and mixing the silica na- noparticles, the polyether amine D-400 and the hydrophobically modified E-42 epoxy resin well by ultrasonic emulsification and high-speed shearing to obtain a resin slurry I; adding 5 g of hydrophobically modified E-42 epoxy resin and 2g of polyether amine D-400 to 5 g of acetone diluent, stirring and mixing well to obtain a resin slurry II; (2) coating the resin slurry II on a substrate with a coating surface density of 0.008g/cm*, and curing at 90°C for 20 min; impregnating the silicon carbide fiber membrane in the resin slurry I, then volatilizing to remove the acetone in the resin slurry I in the silicon carbide fiber membrane, and repeating the above impregnation and volatilization processes for 3 times; and (3) superposing the impregnated silicon carbide fiber mem- brane on the substrate coated with the resin slurry II, heating and curing at 85 °C for 1 h and 95 °C for 1 h to obtain a mechani- cally durable superhydrophobic nano-coating.

The superhydrophobic nano-coating has uniform nanoparticles on the surface, with an average water contact angle of 158.2°; af- ter sanding with a 600-mesh sandpaper for 60 times, the contact angle is 151.5°, a nanofiber skeleton, silica nanoparticles and an epoxy resin are exposed on the surface, with an enlarged surface structure as shown in FIG. 4a; after sanding with a 360-mesh sand- paper for 100 times, the surface water contact angle is 147.3°;

after adhesion with 3M tape for 10 times, the surface water con- tact angle is 148.6°; and after 50 times of gravel impact tests, the contact angle of the superhydrophobic composite is 150.2°;

FIG. 4b is a picture of hydrophobicity of the superhydrophobic coating obtained in the embodiment after being sanded with a 600- mesh sandpaper for 60 times, indicating that the superhydrophobic nano-coating obtained in the embodiment has high hydrophobicity.

The results show that the superhydrophobic nano-coating with a silicon carbide nanofiber membrane as a skeleton can keep superhy- drophobicity under friction, adhesion and dynamic impact, indicat- ing that the superhydrophobic nano-composite has good durability.

Comparative Example 1

The preparation process in the comparative example is the same as that in Embodiment 1, but differs only in that the resin slurry I is directly sprayed on a semi-cured resin slurry II with- out adding a nanofiber skeleton to the superhydrophobic coating, and the obtained coating is an ordinary superhydrophobic coating.

The obtained ordinary superhydrophobic coating has surface morphology similar to that in FIG. la, with uniformly distributed nanoparticles on the surface. However, after stripping with a tape for 5 times, the superhydrophobic surface coating sheds and the water contact angle decreases to 110.8°. The stripped superhydro- phobic coating has morphology as shown in FIG. 5a, and contains only a small amount of nanoparticles, a micro-nano structure is not constructed, resulting in loss of superhydrophobicity, indi- cating that nanofiber mats play a crucial role in the connection of the resin slurry I and the resin slurry I, which can not only enhance the role of the resin slurry I, but also play a role in transitional connection, so that the resin slurry I and the resin slurry I work together to enhance the mechanical durability of the superhydrophobic coating. In addition, it can be seen from FIG. 5b that the ordinary superhydrophobic coating obtained in the compar- ative example has poor hydrophobicity after stripping.

Comparative Example 2

The preparation process in the comparative example is the same as that in Embodiment 3, but differs only in that the resin slurry II has a coating surface density of 0.016 g/cm’ in step (2).

FIG. 6a is an optical picture showing interior of the ob- tained hydrophobic coating. The fiber coating is completely soaked by underlying resin due to excessive surface density of the under- lying resin. The surface morphology of the fiber coating is shown in FIG. 6b, the micro-nano surface structure is lost, and the wa- ter contact angle of the coating is only 108°, indicating that the coating surface density of the resin slurry II has a great impact on the superhydrophobicity of the coating and must be controlled within a reasonable range.

Claims

CONCLUSIONS

A mechanically durable superhydrophobic nanocoating, characterized in that the nanocoating uses a nanofiber membrane as a backbone reinforcement phase and uses a resin slurry as a matrix phase; wherein the resin suspension comprises a resin suspension I and a resin suspension II; wherein the resin suspension I is a mixture of a hydrophobically modified epoxy resin, nanoparticles and a curing agent; and wherein the resin suspension II is a mixture of a hydrophobically modified epoxy resin and a curing agent; wherein the nanofiber membrane is one of polyvinylidene fluoride fiber membrane, polyacrylonitrile fiber membrane, polystyrene fiber membrane, silicon carbon oxide fiber membrane, silicon carbide fiber membrane, alumina fiber membrane, and zirconia fiber membrane.

A method of manufacturing a mechanically durable superhydrophobic nanocoating comprising the steps of: (1) adding a mixture of a hydrophobically modified epoxy resin, nanoparticles and a curing agent to a diluent, and mixing the nanoparticles, the curing agent and the hydrophobically modified epoxy resin well by ultrasonic emulsification and high-speed shearing to obtain a resin slurry I; adding a hydrophobically modified epoxy resin and a curing agent to a diluent, stirring well and mixing to obtain a resin suspension II; {2} coating the resin suspension II on a substrate and curing at 80°C for 10-40 min; impregnating the nanofiber membrane in the resin suspension I, then volatilizing to remove the diluent in the resin suspension I in the nanofiber membrane, and repeating the above impregnation and volatilization processes several times; and

(3) superimposing the impregnated nanofiber membrane on the substrate coated with the resin suspension II, heating and curing to obtain a mechanically durable superhydrophobic nanocoating; wherein in the resin suspension I, the mass ratio of the hydrophobically modified epoxy resin to the nanoparticles is (1.5-3): 1; and the mass ratio of the diluent to the total mass of the hydrophobically modified epoxy resin, the nanoparticles and the curing agent is (3-5): 1; and in the resin suspension II, the mass ratio of the diluent to the total mass of the hydrophobically modified epoxy resin and the curing agent is (0.5-1.5): 1.