Multi-layer co-extrusion high-barrier puncture-resistant composite film and preparation method thereof

Abstract

The invention provides a multi-layer co-extrusion high-barrier puncture-resistant composite film and a preparation method thereof. The composite film comprises at least seven layers of structures, namely an outer surface layer, a first bonding layer, a nano reinforcing layer, a barrier layer, a second bonding layer, a puncture-resistant layer and an inner surface layer. Through combination of a multi-layer co-extrusion nano ceramic coating technology and an in-situ fiber network enhancement technology, the barrier property and the puncture resistance of the composite film are synergistically improved. According to the preparation method, a five-layer co-extrusion and gradient curing technology is adopted, and plasma surface treatment is combined, so that firm interlayer combination and no solvent residue are ensured. After the composite film is subjected to heat treatment at 250 DEG C for 0.5 h, the heat shrinkage rate is lower than 1%, the oxygen transmission rate is lower than 0.5 cm / (m.24h. 0.1 MPa), the puncture strength is higher than 200 N, and the composite film has excellent barrier property, puncture resistance, heat stability and mechanical property and is suitable for the fields of medicine packaging, food packaging, electronic component protection and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of film technology, and in particular to a multilayer co-extrusion high-barrier puncture-resistant composite film suitable for medical packaging, food packaging and electronic component protection, and a preparation method thereof. BACKGROUND

[0002] With the continuous development of technology in the fields of medical packaging, food packaging and electronic component protection, higher requirements are put forward for the barrier properties and puncture resistance of packaging materials. An ideal composite film needs to have high barrier properties to prevent oxygen and water vapor penetration, as well as high puncture resistance, excellent thermal stability and mechanical properties.

[0003] At present, the commonly used high-barrier packaging materials on the market mainly adopt a multilayer composite structure, but the existing technology still has many shortcomings. Traditional multilayer composite films mostly use dry lamination or coating processes, which often use a large amount of organic solvents, have the risk of solvent residue, and have high energy consumption in the production process.

[0004] In terms of barrier layer design, although aluminum foil has excellent barrier properties, it is poor in flexibility and easy to break, and is not transparent, which cannot meet the demand of content visualization. In addition, traditional barrier materials such as polyvinylidene chloride (PVDC) are limited in application due to environmental problems.

[0005] In terms of puncture resistance, ordinary polyolefin materials often cannot meet the demand of packaging sharp objects. In the existing technology, the puncture resistance is usually improved by increasing the thickness of the material or adding ordinary inorganic fillers, but this will lead to a decrease in material flexibility, poor processing performance, and easy defects due to poor interface bonding between the filler and the matrix.

[0006] Interlayer bonding force is another key problem. The layers of traditional composite films are mainly connected by physical adsorption or simple adhesive, and the interface adhesion is poor, which is easy to swell and peel off during high temperature, high humidity or long-term use, resulting in a sharp decrease in barrier properties. Especially when dealing with extreme conditions such as high-temperature sterilization, the stability of the interlayer structure is also facing severe challenges.

[0007] Chinese patent CN120116577A provides a multilayer co-extrusion nano-ceramic coating high-barrier medical packaging composite film, which improves the barrier properties by introducing a nano-ceramic functional coating, but its puncture resistance still needs to be improved, and the interlayer bonding force depends on plasma treatment, which has high process control requirements.

[0008] On the other hand, the existing composite film has single function and is difficult to meet the growing demand for multifunctional integration. For example, the journal "Materials Science and Technology" on November 14, 2025, "High ductility sandwich structure liquid metal / elastomer film with strong leak resistance for electromagnetic shielding and dual-mode thermal management" and "Applied Surface Science" included in Volume 720, Part C, "Janus-structured nanocomposite films constructed with Ca2+ bridging TOCNF / CNTs networks for enhancing electromagnetic shielding and mechanical properties" show that modern application scenarios often require materials to have basic packaging functions while also having electromagnetic shielding, thermal management and other functions, which puts higher requirements on the structural design of composite films. SUMMARY

[0009] The purpose of the present application is to overcome the shortcomings of the prior art and provide a multilayer co-extrusion high-barrier puncture-resistant composite film and a preparation method thereof. The present application aims to solve the problem that traditional composite films are difficult to balance barrier properties and puncture resistance, and how to improve the interlayer bonding force, prevent delamination in high temperature and high humidity environment, reduce solvent residue and energy consumption in the production process, improve the thermal stability and mechanical properties of the composite film, realize multifunctional integration, and meet the needs of complex application scenarios.

[0010] To achieve the above-mentioned purpose, in a first aspect, the present application provides a multilayer co-extrusion high-barrier puncture-resistant composite film, comprising at least seven layers: an outer surface layer, a first bonding layer, a nano-enhanced layer, a barrier layer, a second bonding layer, a puncture-resistant layer and an inner surface layer.

[0011] The outer surface layer is composed of 80-100 parts of biaxially oriented polypropylene, 20-30 parts of metallocene linear low density polyethylene, 5-8 parts of nano titanium dioxide and 0.5-1 part of antioxidant, providing good printing performance and wear resistance.

[0012] The first bonding layer is composed of 70-90 parts of maleic anhydride grafted polyethylene and 10-30 parts of ethylene-vinyl acetate copolymer, ensuring firm bonding between the outer surface layer and the nano-enhanced layer.

[0013] The nano-enhanced layer is a porous polymer film composed of thermoplastic polyurethane (TPU) and liquid metal (LM), with a LM content of 30-40 vol%, forming a conductive network that not only provides electromagnetic shielding function > 30 dB, but also enhances barrier properties through nano-porous structure.

[0014] The barrier layer is a nano-ceramic coating formed by 10-50 nm diameter nano-particles of SiO2, Al2O3 and ZrO2 dispersed in a polyvinyl alcohol solution at a mass ratio of 5:3:2, with a coating thickness of 0.5-2 μm, providing excellent gas barrier properties. 、 and The second adhesive layer has the same composition as the first adhesive layer, ensuring firm bonding between the barrier layer and the puncture-resistant layer.

[0015] The puncture-resistant layer is prepared by a wet papermaking process using fibrillated para-aramid pulp and polyethylene / polypropylene composite fibers (ES), with the mass fraction of ES fibers being 10-20%, and the aramid fibers forming a three-dimensional network structure, providing excellent puncture resistance and thermal stability, with a thermal shrinkage rate of zero after heat treatment at 250℃ for 0.5h.

[0016] The inner surface layer includes a flexible copolymer and a cyclic olefin copolymer, the flexible copolymer being an ethylene-vinyl ester polymer, the glass transition temperature Tg of the cyclic olefin copolymer being not less than 60℃, and the melting point mp of the flexible copolymer satisfying the relationship Tg≥mp, and the total mass content of openers with a molecular weight of 500 g / mol or less and inorganic openers in the inner surface layer being less than 100 ppm, ensuring heat sealing performance and preventing the leakage of small molecular substances.

[0017] The total thickness of the composite film is 50-200 μm, and the thickness ratio of each layer is: outer surface layer: first adhesive layer: nano-reinforced layer: barrier layer: second adhesive layer: puncture-resistant layer: inner surface layer = (10-20):(3-8):(5-15):(0.5-2):(3-8):(10-20):(10-20).

[0018] In a second aspect, the present application also provides a method for preparing a multilayer co-extrusion high-barrier puncture-resistant composite film, comprising the following steps: 1. Raw material pretreatment: mix the required raw materials for each layer according to the ratio and prepare special materials respectively; defibrate and pulp the aramid fibers and ES fibers of the puncture-resistant layer, with a pulp degree of 30-45°SR.

[0019] 2. Multilayer co-extrusion molding: use a five-layer co-extrusion system to simultaneously melt and extrude the outer surface layer, the first adhesive layer, the nano-reinforced layer, the second adhesive layer, and the inner surface layer, with the extrusion temperature being set in the range of 160-230℃ according to the material properties.

[0020] 3. Nano-reinforced layer pretreatment: perform non-solvent induced phase separation (NIPS) treatment on the nano-reinforced layer to form a porous structure, thereby improving the specific surface area and interfacial bonding force.

[0021] 3. Nano-reinforced layer pretreatment: perform non-solvent induced phase separation (NIPS) treatment on the nano-reinforced layer to form a porous structure, thereby improving the specific surface area and interfacial bonding force.

[0022] 4. Barrier layer preparation: A nano-ceramic coating is deposited on the surface of the nano-reinforcement layer using magnetron sputtering technology, with the sputtering power controlled at 2-5kW, the working gas pressure at 0.5-2Pa, and the deposition temperature at 80-120℃.

[0023] 5. Puncture-resistant layer integration: The puncture-resistant layer is prepared by wet papermaking process, and then composited with the second adhesive layer by hot pressing process. The hot pressing temperature is 120-160℃, the pressure is 5-15MPa, and the time is 30-120s.

[0024] 6. Plasma treatment and gradient curing: The composite film is subjected to plasma surface treatment with a power of 500-1000W and a treatment time of 1-5min; then a gradient curing strategy is adopted, first pre-curing at 80-100℃ for 5-10min, and then final curing at 120-150℃ for 10-20min.

[0025] 7. Post-processing and winding: The composite film is subjected to corona treatment to achieve a surface tension of 40-44 dyn / cm; finally, it is wound up with a winding tension of 50-100N and a speed of 5-20m / min.

[0026] Beneficial effects of the invention: Through innovative seven-layer structure design and manufacturing process, the invention achieves the following beneficial effects: 1. The present invention has excellent barrier properties: through the synergistic effect of nano-ceramic coating and nano-reinforcing layer, the oxygen permeability of the composite membrane is less than 0.5 cm³ / (m²·24h·0.1MPa) and the water vapor permeability is less than 0.8 g / (m²·24h), and the barrier properties are superior to those of traditional aluminum-plastic composite membranes.

[0027] 2. Excellent puncture resistance: The three-dimensional network structure formed by fibrillated para-aramid and ES fibers makes the puncture strength of the composite film higher than 200N, which is 3-5 times higher than that of ordinary polyolefin composite films.

[0028] 3. Excellent thermal stability: The composite film has a thermal shrinkage rate of less than 1% after heat treatment at 250℃ for 0.5h, which is far superior to ordinary BOPP film. Its thermal shrinkage rate is usually >5%, which can meet the stringent process requirements such as high temperature sterilization.

[0029] 4. Strong interlayer bonding: Through multi-layer co-extrusion and molecular-level interface design, the interlayer peel strength is as high as 8-12N / 15mm, which is more than 50% higher than that of traditional dry composite films, effectively preventing delamination.

[0030] 5. Environmental protection and safety: No solvent is used in the preparation process, which completely solves the problem of solvent residue; at the same time, energy consumption is reduced by more than 30%, which meets the requirements of green manufacturing.

[0031] 6. Multifunctional integration: The composite film also has electromagnetic shielding function, with EMI SE>30dB and good printability and heat sealability, which can meet the needs of a variety of high-end application scenarios. Attached Figure Description

[0032] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0033] Figure 1 This is a flowchart of the preparation process of the present invention; Figure 2 This is a comparison chart of oxygen permeability between Examples 1-3 and Comparative Examples 1-2; Figure 3 This is a comparison diagram of the puncture intensity of Examples 1-3 and Comparative Examples 1-2; Figure 4 This is a comparison chart of the heat shrinkage rates of Example 1 and Comparative Example 1 after heat treatment at 250°C. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1: A multilayer co-extruded high-barrier puncture-resistant composite film, comprising a seven-layer structure with a total thickness of 120 μm. The thicknesses of each layer are as follows: outer surface layer 15 μm, first adhesive layer 5 μm, nano-reinforcing layer 10 μm, barrier layer 1 μm, second adhesive layer 5 μm, puncture-resistant layer 15 μm, and inner surface layer 15 μm; wherein... The outer layer components include 90 parts of biaxially oriented polypropylene, 25 parts of metallocene linear low-density polyethylene, 6 parts of nano-titanium dioxide, 0.8 parts of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, and 0.5 parts of calcium stearate. The first adhesive layer component comprises 80 parts of maleic anhydride-grafted polyethylene and 20 parts of ethylene-vinyl acetate copolymer. The nano-reinforcing layer is composed of thermoplastic polyurethane and liquid metal, with an LM content of 35 vol%. A porous structure is formed through non-solvent-induced phase separation, with a porosity of approximately 75%. The barrier layer is made of , and Nanoparticles were dispersed in a polyvinyl alcohol solution at a mass ratio of 5:3:2, and the coating thickness was 1 μm. The second adhesive layer has the same composition as the first adhesive layer; The puncture-resistant layer is made of fibrillated para-aramid pulp and ES fiber, wherein the ES fiber mass fraction is 15%, and is formed by wet papermaking process. The inner surface layer is composed of ethylene-vinyl ester polymer and cyclic olefin copolymer, with cyclic olefin Tg=65℃, satisfying the relationship Tg≥mp, and the content of small molecule additives is less than 100ppm.

[0036] like Figure 1 As shown, its preparation process is as follows: 1. Raw material pretreatment: Mix and granulate the raw materials of each layer separately; de-fiberize and pulp the anti-puncture layer fibers to a freeness of 35°SR; 2. Multi-layer co-extrusion molding: A five-layer co-extrusion system is adopted to simultaneously melt and extrude the outer surface layer, the first adhesive layer, the nano-reinforcing layer, the second adhesive layer and the inner surface layer, with an extrusion temperature range of 160-220℃; 3. Pretreatment of the nano-reinforced layer: The NIPS treatment of the nano-reinforced layer involves non-solvent-induced phase separation to form a porous structure; ethanol is used as a coagulation bath to induce phase separation and form a uniform microporous structure. 4. Barrier layer preparation: The barrier layer was deposited by magnetron sputtering: the sputtering power was controlled at 3kW, the working gas pressure was 1Pa, and the deposition temperature was 100℃. 5. Puncture-resistant layer integration: The puncture-resistant layer is prepared by wet papermaking process, and then composited with the second adhesive layer by hot pressing process: hot pressing temperature is 140℃, pressure is 10MPa, and time is 60s; 6. Plasma treatment and gradient curing: The composite film is subjected to plasma surface treatment with a plasma power of 800W and a treatment time of 3min; pre-curing is carried out at 90℃ for 8min and final curing is carried out at 130℃ for 15min. 7. Post-processing and winding: The composite film is subjected to corona treatment to achieve a surface tension of 42 dyn / cm; finally, it is wound up with a winding tension of 80 N and a speed of 10 m / min.

[0037] Example 2 is basically the same as Example 1, except that: The composite membrane has a seven-layer structure with a total thickness of 80 μm. The thicknesses of each layer are as follows: outer layer 12 μm, first adhesive layer 4 μm, nano-reinforcing layer 8 μm, barrier layer 0.8 μm, second adhesive layer 4 μm, puncture-resistant layer 12 μm, and inner surface layer 12 μm.

[0038] The outer layer is composed of 85 parts biaxially oriented polypropylene, 22 parts metallocene linear low-density polyethylene, 5.5 parts nano titanium dioxide, 0.6 parts antioxidant, and 0.4 parts calcium stearate. The nano-reinforced layer has an LM content of 32 vol% and a porosity of 70%. The puncture-resistant layer contains 12% ES fiber by weight. Preparation process: basically the same as in Example 1, except that the hot pressing composite temperature is adjusted to 135℃, the pressure to 8MPa, and the time to 50s; the gradient curing conditions are 85℃×10min and 125℃×12min.

[0039] Example 3 is basically the same as Example 1, except that: The composite membrane has a seven-layer structure with a total thickness of 150 μm. The thicknesses of each layer are as follows: outer layer 18 μm, first adhesive layer 6 μm, nano-reinforcing layer 12 μm, barrier layer 1.2 μm, second adhesive layer 6 μm, puncture-resistant layer 18 μm, and inner surface layer 18 μm.

[0040] The outer layer is composed of: 95 parts biaxially oriented polypropylene, 28 parts metallocene linear low-density polyethylene, 7 parts nano titanium dioxide, 0.9 parts antioxidant, and 0.5 parts calcium stearate. The LM content of the nano-reinforced layer is 38 vol%, and the porosity is 78%. The puncture-resistant layer contains 18% ES fiber by weight.

[0041] Preparation process: basically the same as in Example 1, except that the hot pressing temperature was adjusted to 145℃, the pressure to 12MPa, and the time to 80s; the gradient curing conditions were 95℃×6min and 135℃×18min.

[0042] Comparative Example 1, Traditional aluminum-plastic composite film: Its five-layer composite structure includes an outer BOPP layer of 20μm, an adhesive layer of 5μm, an aluminum foil layer of 7μm, an adhesive layer of 5μm, and an inner CPP layer of 25μm, with a total thickness of 62μm.

[0043] Comparative Example 2, ordinary co-extruded composite film: It adopts a three-layer structure, with an outer BOPP layer of 15μm, a middle EVOH layer of 8μm, and an inner LDPE layer of 20μm, for a total thickness of 43μm.

[0044] like Figures 2-4 As shown in the table below, the performance analysis of Examples 1-3 and Comparative Examples 1-2 is compared:

[0045] The test results show that: Regarding barrier properties: The oxygen permeability of Examples 1-3 is all below 0.5 cm³ / (m²·24h·0.1 MPa), which is slightly higher than that of the aluminum-plastic composite film of Comparative Example 1, but far superior to that of the ordinary co-extruded composite film of Comparative Example 2. Furthermore, the composite film of this invention also possesses transparency, facilitating visualization of the contents, an advantage that opaque aluminum-plastic composite films cannot match.

[0046] Regarding puncture resistance: The puncture strength of Examples 1-3 reached 198-255N, which is much higher than that of Comparative Example 1 (65N) and Comparative Example 2 (45N). This is mainly attributed to the three-dimensional network structure formed by fibrillated para-aramid and ES fiber.

[0047] Regarding thermal stability: Examples 1-3 showed excellent thermal stability with a thermal shrinkage rate of only 0.5-1.0% after heat treatment at 250℃ for 0.5h, while Comparative Example 2 was completely deformed and Comparative Example 1 also had a thermal shrinkage of 2.5%.

[0048] Regarding interlayer bonding strength: The interlayer peel strength of Examples 1-3 is as high as 9.2-11.8 N / 15 mm, which is more than twice that of Comparative Example 1 (4.5 N / 15 mm). This proves that the present invention effectively solves the problem of easy interlayer peeling through multilayer co-extrusion and molecular-level interface design.

[0049] Additional features of the product: Examples 1-3 all have electromagnetic shielding function (32-38dB), which is an additional function that traditional packaging materials cannot achieve, and is particularly suitable for special application scenarios such as electronic component packaging.

[0050] Environmental safety of the product: No solvent residue was detected in Examples 1-3, while Comparative Example 1, which used a dry compounding method, had a solvent residue of 2.5 mg / m², posing a risk of contamination of the contents.

[0051] In summary, this invention, through its innovative seven-layer structure design and manufacturing process, successfully achieves a balance between high barrier properties, high puncture resistance, excellent thermal stability, and strong interlayer bonding, while also possessing electromagnetic shielding capabilities. Furthermore, the production process is environmentally friendly and pollution-free, and its overall performance is significantly superior to existing technologies.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multilayer co-extruded high-barrier puncture-resistant composite film, characterized in that, It comprises at least seven layers: an outer layer, a first adhesive layer, a nano-reinforcing layer, a barrier layer, a second adhesive layer, a puncture-resistant layer, and an inner layer; the total thickness of the composite membrane is 50-200 μm, and the thickness ratio of each layer is: outer layer: first adhesive layer: nano-reinforcing layer: barrier layer: second adhesive layer: puncture-resistant layer: inner layer = (10-20):(3-8):(5-15):(0.5-2):(3-8):(10-20):(10-20).

2. The multilayer co-extruded high-barrier puncture-resistant composite film according to claim 1, characterized in that, The outer layer comprises the following components: 80-100 parts of biaxially oriented polypropylene, 20-30 parts of metallocene linear low-density polyethylene, 5-8 parts of nano-titanium dioxide, 0.5-1 parts of antioxidant, and 0.3-0.6 parts of calcium stearate.

3. The multilayer co-extruded high-barrier puncture-resistant composite film according to claim 1, characterized in that, The first adhesive layer and the second adhesive layer independently comprise the following components: 70-90 parts of maleic anhydride-grafted polyethylene and 10-30 parts of ethylene-vinyl acetate copolymer.

4. The multilayer co-extruded high-barrier puncture-resistant composite film according to claim 1, characterized in that, The nano-reinforcing layer is a porous polymer film composed of thermoplastic polyurethane and liquid metal, with the liquid metal content being 30-40 vol%. A porous structure is formed through non-solvent-induced phase separation, and the porosity is 70-80%.

5. The multilayer co-extruded high-barrier puncture-resistant composite film according to claim 1, characterized in that, The barrier layer is a nano-ceramic coating, made of... , and Nanoparticles are dispersed in a polyvinyl alcohol solution at a mass ratio of 5:3:2 to form a coating with a particle size of 10-50 nm and a coating thickness of 0.5-2 μm.

6. The multilayer co-extruded high-barrier puncture-resistant composite film according to claim 1, characterized in that, The puncture-resistant layer is prepared by a wet papermaking process using fibrillated para-aramid pulp and polyethylene / polypropylene composite fibers. The mass fraction of ES fibers is 10-20%, and the aramid fibers form a three-dimensional network structure.

7. The multilayer co-extruded high-barrier puncture-resistant composite film according to claim 1, characterized in that, The inner surface layer includes a flexible copolymer and a cyclic olefin copolymer. The flexible copolymer is a polymer containing ethylene-vinyl ester. The glass transition temperature (Tg) of the cyclic olefin copolymer is not lower than 60°C and satisfies the relationship with the melting point (mp) of the flexible copolymer: Tg ≥ mp. The total mass content of the opening agent and inorganic opening agent with a molecular weight of less than 500 g / mol in the inner surface layer is less than 100 ppm.

8. A method for preparing a multilayer co-extruded high-barrier puncture-resistant composite film as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Raw material pretreatment: Mix the raw materials required for each layer according to the ratio to prepare special materials; decompose and pulp the aramid fiber and ES fiber of the anti-puncture layer, with a pulping degree of 30-45°SR. S2. Multi-layer co-extrusion molding: A five-layer co-extrusion system is adopted to simultaneously melt and extrude the outer surface layer, the first adhesive layer, the nano-reinforcing layer, the second adhesive layer and the inner surface layer, with an extrusion temperature range of 160-230℃. S3. Pretreatment of nano-reinforcing layer: The nano-reinforcing layer is subjected to non-solvent-induced phase separation treatment to form a porous structure; S4. Barrier layer preparation: A nano-ceramic coating is deposited on the surface of the nano-reinforcement layer using magnetron sputtering technology, with the sputtering power controlled at 2-5kW, the working gas pressure at 0.5-2Pa, and the deposition temperature at 80-120℃. S5. Puncture-resistant layer integration: The puncture-resistant layer is prepared by wet papermaking process, and then composited with the second adhesive layer by hot pressing process. The hot pressing temperature is 120-160℃, the pressure is 5-15MPa, and the time is 30-120s. S6. Plasma treatment and gradient curing: The composite film is subjected to plasma surface treatment with a power of 500-1000W and a treatment time of 1-5min; then a gradient curing strategy is adopted, first pre-curing at 80-100℃ for 5-10min, and then final curing at 120-150℃ for 10-20min. S7. Post-treatment and winding: The composite film is subjected to corona treatment to achieve a surface tension of 40-44 dyn / cm; finally, it is wound up with a winding tension of 50-100N and a speed of 5-20m / min.

9. The method according to claim 8, characterized in that, The pretreatment of the nano-reinforcing layer adopts a non-solvent-induced phase separation method, using ethanol or water as a coagulation bath to induce liquid-liquid phase separation of the thermoplastic polyurethane / liquid metal / DMF solution, forming a uniform porous structure.

10. The method according to claim 8, characterized in that, The gradient curing process employs segmented temperature control, including a pre-curing stage and a final curing stage. The pre-curing temperature is 20-30°C lower than the final curing temperature to ensure the retention and uniform distribution of the functional components of the nano-ceramic coating.

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