Super-hydrophobic polylactic acid film having long-lasting self-cleaning performance and preparation method therefor

Abstract

Disclosed in the present invention are a super-hydrophobic polylactic acid film having long-lasting self-cleaning performance and a preparation method therefor, belonging to the technical field of materials. The method comprises: by using polylactic acid as a main material, polymerized rosin as a pore-foaming agent and toluene as an extraction agent, performing non-solvent induced phase separation to prepare a polylactic acid porous film; and then soaking same in a hydrophobic substance solution so as to obtain the super-hydrophobic polylactic acid film. The super-hydrophobic polylactic acid film obtained in the present invention has an initial water contact angle reaching 150 degrees or above, and has super-hydrophobicity and a remarkable self-cleaning effect. In addition, after a plurality of times of rubbing, 94% or above of the water contact angle of the film can be kept and the self-cleaning property is still remarkable. Therefore, said film has wide application prospects in the fields such as self-cleaning, fluid drag reduction, oil-water separation and icing and corrosion prevention.

Description

A super-hydrophobic polylactic acid film with durable self-cleaning properties and preparation method thereof Technical Field

[0001] The invention relates to a super-hydrophobic polylactic acid film with durable self-cleaning properties and a preparation method thereof, belonging to the technical field of materials. Background Art

[0002] In the modern materials field, applying a hydrophobic coating is one of the primary methods for achieving super-hydrophobic, self-cleaning properties. For example, a hydrophobic coating on glass prevents raindrops from adhering to the surface, and dirt is washed away by raindrops, creating a self-cleaning effect. Currently, super-hydrophobic materials are gaining increasing attention for applications in oil-water separation, anti-icing, and corrosion prevention.

[0003] Polylactic acid (PLA) is a biodegradable, green and environmentally friendly material with excellent film-forming properties and adjustable membrane structure. Methods for preparing PLA porous membranes primarily include electrospinning, supercritical pore generation, particle leaching, respiratory patterning, and phase separation. Relatively speaking, the phase separation method offers a short preparation cycle, simple operation, a mild operating environment, and controllable pore size and morphology. Non-solvent phase separation is also more cost-effective. To achieve lower surface energy, the prepared superhydrophobic material is sometimes surface-modified. Fluorochemicals can impart lower surface energy to the material, but they pose a significant environmental risk and are expensive. Therefore, developing a green and cost-effective method for preparing superhydrophobic PLA porous membranes is highly desirable. Technical issues

[0004] The technical problem to be solved by the present invention is to propose a method for preparing a durable, self-cleaning super-hydrophobic polylactic acid membrane. In this technical solution, by selecting a specific organic solvent, the porogen is removed from the membrane material while the membrane surface is micro-etched. A micro-nanoscale rough structure with a certain depth of micro-gaps and micropores is created on the membrane surface. This increases the penetration of the hydrophobic material into the substrate surface layer, resulting in a relatively strong mechanical engagement between the hydrophobic layer and the substrate surface, thereby achieving the fixation of the hydrophobic layer on the substrate, and obtaining a polylactic acid porous membrane with a water contact angle of more than 150 degrees and durable super-hydrophobicity. Technical Solutions

[0005] In order to achieve the above-mentioned purpose, the technical solution of the present invention is as follows: high molecular weight polylactic acid and a rosin-based small molecule porogen are added to an organic solvent and stirred until completely dissolved to obtain a mixed solution; the obtained mixed solution is subjected to ultrasonic degassing treatment, poured into a glass culture dish, and allowed to stand at room temperature to obtain a polylactic acid film with a thickness of 93 to 111 μm after the solvent evaporates; the polylactic acid film is immersed in a specific organic solvent that has a surface micro-etching effect on polylactic acid and has high solubility for rosin to achieve elution of the porogen and micro-nanoscale etching of the polylactic acid surface, and then dried at room temperature for 3 to 4 hours to obtain a polylactic acid porous membrane with a deep micro-nano pore structure on the surface; and the obtained polylactic acid porous membrane is immersed in a hydrophobic substance suspension to obtain a super-hydrophobic polylactic acid membrane product.

[0006] The method of the present invention uses polylactic acid as a main material and rosin-based small molecules as a porogen to perform solution casting to form a membrane. By selecting a specific organic solvent, the porogen is removed and the surface of the polylactic acid is micro-etched to prepare a polylactic acid porous membrane with a special vertical micro-nano void structure on the surface. Then, a layer of low surface energy material (octadecyltrichlorosilane) is fixed on the surface of the polylactic acid porous membrane by a deposition method to obtain a durable polylactic acid super-hydrophobic film with a surface contact angle of more than 150 degrees and a contact angle maintained at more than 90% after being rubbed five times.

[0007] The present invention provides a method for preparing a durable super-hydrophobic polylactic acid porous membrane, comprising the following steps:

[0008] (1) Dissolving 40-100 parts of polylactic acid and 0-60 parts of polymerized rosin in an organic solvent according to a weight ratio, mixing them evenly, and then evaporating the solvent to form a film; then immersing the film in toluene to obtain a polylactic acid porous film;

[0009] (2) dispersing octadecyltrichlorosilane (OTS) in a solvent, and then adding water to react to obtain an octadecyltriethoxysilane dispersion; soaking the polylactic acid porous membrane obtained in step (1) in the octadecyltriethoxysilane dispersion to obtain a polylactic acid porous membrane with durable superhydrophobicity.

[0010] As an embodiment of the present invention, in step (1), the amount of the organic solvent relative to the total mass of the polylactic acid and the polymerized rosin is 10-30 mL / g, and specifically 20 mL / g.

[0011] As an embodiment of the present invention, in step (1), the organic solvent may be chloroform.

[0012] As an embodiment of the present invention, in step (1), the relative molecular mass of polylactic acid is 0.3~1.5×10 5 .

[0013] As an embodiment of the present invention, in step (1), the polymerized rosin is used as a porogen; preferably, it is an alcohol-soluble polymerized rosin.

[0014] As an embodiment of the present invention, in step (1), the molecular weight of the polymerized rosin is less than 1000.

[0015] As an embodiment of the present invention, in step (1), preferably, 70 parts of polylactic acid and 30 parts of polymerized rosin; or 100 parts of polylactic acid and 0 parts of polymerized rosin.

[0016] As an embodiment of the present invention, in step (1), the external environment temperature of the volatilization solvent is 20-40°C, preferably 25°C.

[0017] As an embodiment of the present invention, in step (2), the solvent is any one or more of petroleum ether, toluene, and n-hexane, preferably n-hexane.

[0018] As an embodiment of the present invention, in step (2), the volume ratio of octadecyltrichlorosilane to the solvent is 1:(10-30), preferably 1:20.

[0019] As an embodiment of the present invention, in step (2), the volume fraction of water relative to the solvent is 0.1%.

[0020] The present invention provides a durable super-hydrophobic polylactic acid porous membrane prepared based on the above method.

[0021] The present invention also provides applications of the above-mentioned durable super-hydrophobic polylactic acid porous membrane in self-cleaning, fluid drag reduction, oil-water separation, and anti-icing and anti-corrosion. Beneficial effects

[0022] The main material used in this invention is polylactic acid, a renewable and biodegradable synthetic polymer. It has abundant raw material sources and excellent biodegradability, completely degrading into water and carbon dioxide. The porogen, polymerized rosin, is naturally derived and biodegradable, exhibiting excellent compatibility, durability, and antioxidant properties. By removing the porogen with a specific solvent and simultaneously micro-etching the material surface, a surface with a unique micro-nanostructured depth of micro-voids is created, providing excellent attachment sites for hydrophobic substances.

[0023] The micro-nano voids with a special longitudinal structure obtained by the present invention can enable the hydrophobic substance to be firmly attached to the surface of the polylactic acid film through the mechanical nesting effect at the micro-nano scale, thereby improving the self-cleaning and super-hydrophobic durability of the polylactic acid film and solving the problem of the short effectiveness of the hydrophobic material during use.

[0024] The self-cleaning, super-hydrophobic polylactic acid porous membrane prepared by the present invention has good durability in super-hydrophobic self-cleaning properties (still has good hydrophobicity after 5 friction cycles), and has great application potential in anti-fouling and oil prevention, oil-water separation, seawater purification, composite materials, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 shows SEM images (1000x magnification) of the polylactic acid porous membranes prepared in Examples 1, 2, and 3 of the present invention after toluene treatment and before superhydrophobic treatment: PLA / PR miscibility ratios are (a) 100 / 0; (b) 90 / 10; (c) 80 / 20; (d) 70 / 30; (e) 60 / 40; (f) 50 / 50; and (g) 40 / 60. Additionally, (a1) and (d1) are SEM images at 7000x magnification of PLA / PR miscibility ratios of 100 / 0 and 70 / 30, respectively.

[0026] Figure 2 is an SEM photograph (magnification 1000 times) of the polylactic acid porous membranes prepared in Comparative Examples 1 and 2 of the present invention after toluene treatment: PLA / PR miscibility ratios are (a) 100 / 0; (b) 90 / 10; (c) 80 / 20; (d) 70 / 30; (e) 60 / 40; (f) 50 / 50; and (g) 40 / 60.

[0027] Figure 3 is an SEM photograph (magnification 1000x) of the polylactic acid porous membrane prepared in Comparative Example 3 of the present invention after treatment with petroleum ether and n-hexane and before superhydrophobic treatment: the PLA / PR miscibility ratio is 70 / 30, and the treated organic solvent is (a) petroleum ether; (b) n-hexane.

[0028] Figure 4 is an infrared spectra of the 70 / 30 PLA / PR film prepared in Example 2 of the present invention before toluene treatment (top, polylactic acid-polymerized rosin composite film), after toluene treatment (center, pure polylactic acid film), and after superhydrophobic treatment (bottom, superhydrophobic polylactic acid film).

[0029] Figure 5 is a diagram showing the self-cleaning effect of the self-cleaning, super-hydrophobic polylactic acid porous membranes prepared in Examples 1 and 2 of the present invention (PLA / PR miscibility ratio of 70 / 30) and the non-hydrophobic polylactic acid porous membranes prepared in Comparative Examples 1 and 2 (PLA / PR miscibility ratio of 70 / 30) on rhodamine dye.

[0030] FIG6 is a diagram showing the self-cleaning effect of the self-cleaning, super-hydrophobic polylactic acid porous membrane prepared in Examples 1 and 2 of the present invention on rhodamine dye after five friction cycles.

[0031] FIG7 shows the preparation principle of the self-cleaning, super-hydrophobic polylactic acid hydrophobic membrane prepared in Examples 1 and 2 of the present invention. Best Mode for Carrying Out the Invention

[0032] Weigh 1 g of particles (PLA / PR mass ratio of 7 / 3) and dissolve them in 20 mL of chloroform with magnetic stirring until completely dissolved. Then pour the solution into a 9 cm diameter glass dish and incubate at room temperature until the solvent completely evaporates. After removing the membrane, soak it in 20 mL of toluene solution for 1 min to obtain a PLA porous membrane.

[0033] 1 mL of OTS was added to 20 mL of n-hexane. 20 μL of water was then pipetted into the mixture and ultrasonically dispersed for 1 hour to obtain a hydrophobic octadecyltriethoxysilane solution. The membrane was then immersed in the treated hydrophobic solution for 30 seconds and removed to obtain a PLA hydrophobic porous membrane. Modes for Carrying Out the Invention

[0034] The following describes preferred embodiments of the present invention. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0035] The polylactic acid particles involved in the present invention can be purchased from Anhui Fengyuan Futailai Polylactic Acid Co., Ltd. Polylactic acid particles FY604; polymerized rosin particles with a specification of industrial 140 can be purchased from Shenzhen Jitian Chemical Co., Ltd., with a softening point of 135-145°C and an acid value of 140 mgKOH / g.

[0036] Example 1

[0037] 1 g of PLA particles was weighed and dissolved in 20 mL of chloroform, and magnetic stirring was applied until completely dissolved. The solution was then poured into a 9 cm diameter glass dish and incubated at room temperature until the solvent was completely evaporated. The membrane was removed and soaked in 20 mL of toluene solution for 1 min to obtain a PLA porous membrane.

[0038] 1 mL of OTS was added to 20 mL of n-hexane. 20 μL of water was then pipetted into the mixture and ultrasonically dispersed for 1 hour to obtain a hydrophobic octadecyltriethoxysilane solution. The membrane was then immersed in the treated hydrophobic solution for 30 seconds and removed to obtain a PLA hydrophobic porous membrane.

[0039] Example 2

[0040] Weigh 1 g of particles (PLA / PR mass ratio of 7 / 3) and dissolve them in 20 mL of chloroform with magnetic stirring until completely dissolved. Then pour the solution into a 9 cm diameter glass dish and incubate at room temperature until the solvent completely evaporates. After removing the membrane, soak it in 20 mL of toluene solution for 1 min to obtain a PLA porous membrane.

[0041] 1 mL of OTS was added to 20 mL of n-hexane. 20 μL of water was then pipetted into the mixture and ultrasonically dispersed for 1 hour to obtain a hydrophobic octadecyltriethoxysilane solution. The membrane was then immersed in the treated hydrophobic solution for 30 seconds and removed to obtain a PLA hydrophobic porous membrane.

[0042] Example 3

[0043] Weigh 1 g of particles (PLA / PR mass ratios of 90 / 10, 80 / 20, 60 / 40, 50 / 50, and 40 / 60), dissolve them in 20 mL of chloroform, and stir magnetically until completely dissolved. Then, pour the solution into a 9-cm diameter glass dish and incubate at room temperature until the solvent completely evaporates. After removing the membrane, soak it in 20 mL of toluene solution for 1 min to obtain a PLA porous membrane.

[0044] 1 mL of OTS was added to 20 mL of n-hexane. 20 μL of water was then pipetted into the mixture and ultrasonically dispersed for 1 hour to obtain a hydrophobic octadecyltriethoxysilane solution. The membrane was then immersed in the treated hydrophobic solution for 30 seconds and removed to obtain a PLA hydrophobic porous membrane.

[0045] Comparative Example 1

[0046] Refer to Example 1, except that no hydrophobic substance solution is added, and other conditions are the same as Example 1.

[0047] The specific operation steps are as follows: weigh 1g of PLA particles and dissolve them in 20mL of chloroform, and stir magnetically until completely dissolved; then pour the solution into a glass dish with a diameter of 9cm and incubate at room temperature until the solvent completely evaporates; after removing the membrane, soak it in 20mL of toluene solution for 1 minute to obtain a PLA porous membrane.

[0048] The experimental results show that the PLA film prepared without adding hydrophobic substances does not have a superhydrophobic structure, and the hydrophobic substance solution has a decisive influence on the preparation of self-cleaning, superhydrophobic PLA porous membrane.

[0049] Comparative Example 2

[0050] Refer to Example 1, except that no hydrophobic solution is added, and the proportion of PR is adjusted from 0% to 10%, 20%, 30%, 40%, 50%, 60%, and 70% in Example 1. Other conditions are the same as in Example 1.

[0051] The specific operation steps are as follows: weigh 1g of particles (PLA / PR mass ratio is 90 / 10, 80 / 20, 60 / 40, 50 / 50, 40 / 60, 30 / 70) and dissolve it in 20mL of chloroform, and stir magnetically until completely dissolved; then pour the solution into a 9cm diameter glass dish and incubate at room temperature until the solvent completely evaporates; after removing the membrane, soak it in 20mL of toluene solution for 1min to obtain a PLA porous membrane.

[0052] The experimental results show that the polylactic acid membrane prepared without adding hydrophobic substances does not have a superhydrophobic structure, and the hydrophobic substance solution has a decisive influence on the preparation of self-cleaning, superhydrophobic polylactic acid porous membrane.

[0053] The hydrophobic properties of the hydrophobic membranes obtained in the examples and comparative examples were measured, and the results are shown in Table 1.

[0054] Table 1 Performance results of polylactic acid super-hydrophobic films prepared in Examples and Comparative Examples

[0055]

[0056] NA means no test was performed.

[0057] Morphological characterization:

[0058] In Figure 1(a), the pure PLA system, after toluene etching, forms interlocking spherical protrusions. These exposed spherical protrusions are mostly around 10 μm in diameter, and numerous evenly distributed nanoscale circular depressions are also present on the protrusions. This is likely the result of toluene etching PLA. Figure 1(a1) shows that these uniform cracks are around 500 nm in size. Figures 1(b) and 1(c) show that the surface exhibits micro-nanoscale grooves after toluene etching at 10% and 20% PR content. These grooves are mostly below 2 μm in size, with localized circular depressions, but no spherical protrusions. Figure 1(c) shows that at a PR content of 20%, the grooves become larger and localized circular depressions appear. Compared to Figure 1(c), in Figure 1(d), at a PR content of 30%, interlocking spherical protrusions are formed after toluene etching, and the number of circular depressions on the surface increases. Figure 1(d1) shows that these circular depressions are 1-2 μm in diameter and are evenly spaced on the protruding spheres. The samples represented by Figures 1(e), 1(f), and 1(g) show increasing PR content by 10%. During curing, the PR complexes become larger. Toluene dissolves all of the PR and some of the PLA during the etching process, gradually eliminating surface irregularities and pores, improving flatness and weakening hydrophobicity. This indicates that in Examples 1 and 2, the formation of adhered spherical protrusions and the presence of depressions within them increases surface roughness, further contributing to improved hydrophobicity.

[0059] After the hydrophobic treatment, the hydrophobic substance is physically adsorbed on the PLA film, changing the surface morphology. After the hydrophobic treatment of the pure PLA system in Example 1, the hydrophobic substance fills the spherical surface and the circular depressions at the nanometer level on the surface, forming grooves with a diameter of 3-4 μm on the surface. In Example 4-PLA / PR with a miscibility ratio of 90 / 10, the hydrophobic substance fills the micro-nano grooves formed after the composite film is etched with toluene, and forms larger grooves, and the depth of the grooves is smaller than that of Example 1. In Example 4-PLA / PR with a miscibility ratio of 80 / 20, the hydrophobic substance fills the grooves to form a relatively smooth surface, with local nano-scale protrusions and micron-scale cracks. In Example 2, the complex morphology of the original surface is not completely buried by the coating, but retains some micron-level concave-convex morphologies. Example 4-PLA / PR60 / 40, 50 / 50, 40 / 60 shows that since the original surface morphology is relatively flat, the overall concave-convex degree does not increase after applying the hydrophobic coating.

[0060] The infrared spectra of the samples prepared in Example 2 are shown in Figure 4. The strong peaks of the three samples in the spectrum are all at 1750 cm -1 , is the C=O stretching vibration peak, which is a characteristic peak of PLA; Example 2 sample before toluene immersion (top) - at 2900cm –1 There is a peak near 2900cm, which represents the C-H stretching vibration on the saturated C atom, which corresponds to the large amount of –CH3, –CH2- and cis-olefin structures contained in PR. The sample after soaking (middle) does not have a peak at 2900cm –1 The characteristic peak of PR is located at 2916 cm-1, which confirms that PR as a porogen is completely removed and the prepared PLA porous membrane is composed of pure PLA. After the membrane sample is hydrophobic treated (bottom), two peaks similar to those of hydrophobic substances are added at 2916 cm-1. -1 and 2848 cm -1 The former is a -CH2-CH2-antisymmetric stretching vibration peak, while the latter is a -CH2-CH2-symmetric stretching vibration peak. This indicates that there are alkyl chains in the PLA hydrophobic film, which means that the hydrophobic substance has been attached to the PLA film.

[0061] Comparative Example 3

[0062] Referring to Example 2, the toluene solution was replaced with petroleum ether and n-hexane as shown in Table 2, and other conditions remained unchanged to prepare the corresponding membrane products. The hydrophobic properties of the membrane products were measured, and the results are shown in Table 2.

[0063] Table 2 Hydrophobic properties of membrane products prepared with different solvents

[0064] Solvent Water contact angle (°) Water contact angle after 5 friction cycles (°) Toluene (Example 2) 150.64 141.74 Petroleum ether 118.72 112.51 n-Hexane 128.32 108.49

[0065] Testing of self-cleaning, super-hydrophobic polylactic acid porous membrane:

[0066] The self-cleaning effects of the samples prepared in Examples 1 and 2 and Comparative Examples 1 and 2 on rhodamine dye are shown in Figure 5. As shown in Figure 4, since rhodamine dye turns red when exposed to water, the dye remaining on the membrane surface after rinsing with water droplets dyes the PLA porous membrane in Comparative Example 1 red. However, after the hydrophobic treatment of Examples 1 and 2, the rhodamine dye failed to stain the surface of the hydrophobic membrane. After rinsing with distilled water, the membrane surface remained largely clean, demonstrating that the hydrophobic membrane can resist contamination by some pollutants and has good self-cleaning capabilities.

[0067] The self-cleaning, superhydrophobic PLA porous membranes prepared in Examples 1 and 2 after five friction cycles demonstrate their self-cleaning properties against rhodamine dye, as shown in Figure 6. The figure demonstrates that after five high-intensity friction cycles, the superhydrophobic PLA membrane containing 30% PR maintains excellent cleaning performance against rhodamine dye, demonstrating that external forces have little effect on the superhydrophobic PLA membrane. However, the superhydrophobic PLA membrane containing pure PLA exhibits a reduced cleaning performance against rhodamine dye, demonstrating that superhydrophobic PLA membranes containing a certain PR content in a miscible system possess persistent self-cleaning properties.

[0068] The preparation principle of the self-cleaning, super-hydrophobic PLA hydrophobic films prepared in Examples 1 and 2 is shown in Figure 7. As can be seen, after toluene etching, the film obtained from the pure PLA system exhibits only a few small depressions and grooves on the surface. After the hydrophobic treatment, octadecyltriethoxysilane does not adhere firmly to the film surface, and after friction, only a small amount of hydrophobic material remains on the film surface. In contrast, the composite film obtained from the specific PLA-PR (PLA / PR mass ratio of 70 / 30) miscible system exhibits deep depressions and grooves after toluene etching. After the hydrophobic treatment, octadecyltriethoxysilane adheres firmly to the surface, and after friction, a large amount of hydrophobic material remains on the film surface, supporting the film's self-cleaning and super-hydrophobic properties. Industrial Applicability

[0069] The main material used in this invention is polylactic acid, a renewable and biodegradable synthetic polymer. It has abundant raw material sources and excellent biodegradability, completely degrading into water and carbon dioxide. The porogen, polymerized rosin, is naturally derived and biodegradable, exhibiting excellent compatibility, durability, and antioxidant properties. By removing the porogen with a specific solvent and simultaneously micro-etching the material surface, a surface with a unique micro-nanostructured depth of micro-voids is created, providing excellent attachment sites for hydrophobic substances.

[0070] The micro-nano voids with a special longitudinal structure obtained by the present invention can enable the hydrophobic substance to be firmly attached to the surface of the polylactic acid film through the mechanical nesting effect at the micro-nano scale, thereby improving the self-cleaning and super-hydrophobic durability of the polylactic acid film and solving the problem of the short effectiveness of the hydrophobic material during use.

[0071] The self-cleaning, super-hydrophobic polylactic acid porous membrane prepared by the present invention has good durability in super-hydrophobic self-cleaning properties (still has good hydrophobicity after 5 friction cycles), and has great application potential in anti-fouling and oil prevention, oil-water separation, seawater purification, composite materials, etc.

Claims

1. A method for preparing a superhydrophobic polylactic acid porous membrane, characterized in that, it comprises the following steps: (1) According to the weight part ratio, dissolve 40 - 100 parts of polylactic acid and 0 - 60 parts of polymerized rosin in an organic solvent, mix well, and then volatilize the solvent to form a membrane; then soak the membrane in toluene to obtain a polylactic acid porous membrane; (2) Disperse octadecyltrichlorosilane in a solvent, and then add water for reaction to obtain an octadecyltriethoxysilane dispersion; soak the polylactic acid porous membrane obtained in step (1) in the octadecyltriethoxysilane dispersion to obtain a polylactic acid porous membrane with durable superhydrophobicity.

2. The method according to claim 1, characterized in that, in step (1), the dosage of the organic solvent relative to the total mass of polylactic acid and polymerized rosin is 10 - 30 mL / g.

3. The method according to claim 1, characterized in that, in step (1), the organic solvent is chloroform.

4. The method according to claim 1, characterized in that, In step (1), the relative molecular mass of polylactic acid is 0.3 to 1.5×10 5 ; the molecular weight of the polymerized rosin is less than 1000.

5. The method according to claim 1, characterized in that, in step (1), according to the weight part ratio, dissolve 70 parts of polylactic acid and 30 parts of polymerized rosin in an organic solvent, mix well, and then volatilize the solvent to form a membrane; then soak the membrane in toluene to obtain a polylactic acid porous membrane.

6. The method according to claim 1, characterized in that, in step (1), according to the weight part ratio, dissolve 100 parts of polylactic acid in an organic solvent, mix well, and then volatilize the solvent to form a membrane; then soak the membrane in toluene to obtain a polylactic acid porous membrane.

7. The method according to claim 1, characterized in that, in step (2), the solvent is any one or more of petroleum ether, toluene, and n - hexane.

8. The method according to claim 1, characterized in that, in step (2), the volume ratio of octadecyltrichlorosilane to the solvent is 1:(10 - 30).

9. A superhydrophobic polylactic acid porous membrane prepared by the method according to any one of claims 1 - 8.

10. The application of the superhydrophobic polylactic acid porous membrane according to claim 9 in self - cleaning, fluid drag reduction, oil - water separation, anti - icing and anti - corrosion.

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