A super-hydrophobic anti-icing POF heat-shrinkable film with wave-absorbing function and a preparation method thereof

Abstract

The application provides a super-hydrophobic anti-icing POF heat shrinkable film with wave-absorbing function and a preparation method thereof. The POF heat shrinkable film comprises two PP outer layers and a PET inner layer. The PET inner layer is a modified PET film, which comprises the following raw materials in percentage by weight: 50-70% of absorbent filler, 5-10% of pigment, 20-35% of resin pellets and 1-5% of auxiliary agent. The POF heat shrinkable film is subjected to PTFE layer plating treatment on the surface of the POF heat shrinkable film to form a super-hydrophobic layer with a water contact angle of more than 150 degrees, thereby fundamentally solving the problem of easy icing on the outer surface of the wind power blade. The PET film is subjected to modification treatment to improve the heat shrinkage rate, and the wave-absorbing material is introduced into the PET inner layer, so that the POF heat shrinkable film has the wave-absorbing function. The POF heat shrinkable film prepared by the application has excellent heat shrinkage performance, super-hydrophobic anti-icing property and wave-absorbing function. When the POF heat shrinkable film is coated on the outer surface of the wind power blade, the scattering intensity of the radar wave by the wind power blade is effectively reduced, the service life of the radar receiving device is improved, and the risk of being burned and damaged is avoided.

Description

Technical Field

[0001] This invention relates to the field of functional polyester heat shrink film technology, specifically to a superhydrophobic anti-icing POF heat shrink film with wave absorption function and its preparation method. Background Technology

[0002] "Peak carbon emissions" refers to the point at which greenhouse gas emissions from the combustion of fossil fuels such as coal, oil, and natural gas, industrial production processes, land use changes, and forestry activities cease to increase and reach their peak before 2030. Wind energy, as a clean and renewable energy source, is highly sought after. China has exploitable wind energy reserves exceeding 1 billion kilowatts. Using wind turbines to convert wind energy into mechanical energy, and then into electricity, can avoid the environmental pollution caused by carbon dioxide and other greenhouse gases from fossil fuel power generation. However, in winter, especially in coastal areas, wind turbine blades are prone to icing, increasing their weight and reducing their efficiency, thus hindering the expansion of the wind power market.

[0003] Mechanical de-icing, heated de-icing, and anti-icing coating are the main de-icing methods currently used. Mechanical de-icing is the most widely used method. While simple to operate, it requires the equipment to be shut down, impacting power generation and consuming significant manpower and resources. Heated de-icing involves connecting a resistor inside or outside the blade; when energized, the resistor heats up and melts the ice layer condensed on the blade surface. While this method saves labor costs, it consumes a large amount of electrical energy. Furthermore, both mechanical and heated de-icing methods can lead to continued icing on the blades, failing to fundamentally prevent this phenomenon. Anti-icing coatings sprayed on the blade surface are often superhydrophobic coatings with low surface energy. While these coatings can prevent ice and snow from condensing, their adhesion to the wind turbine blade surface is weak, making them prone to peeling and aging.

[0004] Besides the three de-icing methods mentioned above, some studies have also shown that POF heat shrink film can be used to wrap the outer surface of wind turbine blades to enhance their anti-icing performance and resistance to UV aging. The principle of POF heat shrink film is to forcibly stretch the polymer in both longitudinal and transverse directions or one direction between its glass transition temperature and viscosity flow temperature, causing the polymer molecular chains to align along the stretching direction. Then, the polymer is rapidly cooled, freezing the molecular orientation. When the film is reheated to the "thawing" temperature, the molecular chains relax, generating relative motion, and the molecules return to their original state, resulting in shrinkage. Commonly used heat shrink films include PVC heat shrink film and PE heat shrink film. While PVC heat shrink film has a high shrinkage rate, the presence of toxic vinyl chloride monomers is environmentally unfriendly; PE heat shrink film is relatively brittle and prone to cracking and deformation. Furthermore, using these heat shrink films alone cannot solve the anti-icing problem.

[0005] In addition, ships equipped with radar transmitting and receiving devices are often seen in coastal areas. The special shape, material and rotation characteristics of wind turbine blades make them strong sources of radar signal scattering, reflecting the emitted radar waves back to the receiving device, thereby interfering with the radar signal and even burning out the precision instruments in the receiving device.

[0006] Therefore, there is an urgent need to develop a new type of heat-shrinkable film that can simultaneously possess the comprehensive properties of heat shrinkability, anti-icing, wave absorption, and ease of construction to meet the usage requirements of wind turbine blades. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the main objective of this invention is to provide a superhydrophobic anti-icing POF heat-shrinkable film with wave-absorbing function and its preparation method. The POF heat-shrinkable film of this invention not only has good heat shrinkage performance and anti-icing properties, but also has wave-absorbing function. When it is wrapped around the outer surface of wind turbine blades, it can effectively reduce the scattering intensity of radar waves by wind turbine blades, improve the service life of radar receiving devices, and avoid the risk of being burned.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A superhydrophobic anti-icing POF heat shrink film with wave absorption function, wherein the structure of the POF heat shrink film includes a PP outer layer, a PET inner layer and a PP outer layer stacked in sequence, wherein the PET inner layer is a modified PET film with wave absorption function and the PP outer layer is a PP film with PTFE coating.

[0010] Preferably, the thickness of the POF heat shrink film does not exceed 300 μm.

[0011] Preferably, the thickness of the PP outer layer does not exceed 25 μm, and the thickness of the PTFE coating does not exceed 1 μm.

[0012] Preferably, the modification of the modified PET film is achieved through physical blending or graft copolymerization, with the aim of reducing its crystallinity and increasing its heat shrinkage rate.

[0013] Preferably, the modified PET film comprises the following raw materials by weight percentage: 50%~70% absorbent filler, 5%~10% pigment, 20%~35% resin granules, and 1%~5% additives.

[0014] Preferably, the absorbent filler comprises one or more of ferromagnetic absorbents, carbon-based absorbents, or semiconductor absorbents;

[0015] The pigment includes one or more of silica and metal oxides;

[0016] The resin granules include one or more of PET and PBT;

[0017] The additives include one or more of plasticizers, stabilizers, opening slip agents, and UV stabilizers.

[0018] More preferably, the plasticizer includes one or more of DOP, DEP, glyceryl trioleate, etc.

[0019] The stabilizer is mainly a heat stabilizer, including one or more of metal soaps, phosphates, and organotin compounds;

[0020] The opening slip agent includes one or more of erucamide and silica;

[0021] The UV absorbers include one or more of the following: salicylates, xylene ketones, benzotriazoles, etc., as well as UV evaluators such as titanium dioxide, zinc oxide, talc, and carbon black.

[0022] Preferably, the PTFE coating is prepared by radio frequency magnetron sputtering of a PTFE target.

[0023] More preferably, before preparing the PTFE coating, the PP film surface is activated by plasma gas impact, which increases the surface roughness of the film and introduces new groups, thereby enhancing the adhesion of the PTFE layer.

[0024] Preferably, the plasma gas is one or more of CF4 or O2.

[0025] This invention also provides a method for preparing the above-mentioned superhydrophobic anti-icing POF heat-shrinkable film with wave-absorbing function, comprising the following steps:

[0026] (1) Mixing: Weigh the raw materials for the outer and inner layers according to the proportions and mix them evenly;

[0027] (2) Feeding: The inner layer mixture is added to the first extruder, and the two sets of outer layer mixtures are added to the second and third extruders. After melt blending, the outer layer melt resin and the inner layer melt resin are obtained respectively.

[0028] (3) Extruded sheet: The inner and outer molten resins extruded by the extruder converge at the three-layer die head to extrude sheet-like melt, which is then cooled on the casting roller to form an unstretched sheet;

[0029] (4) Stretching and shaping: After preheating the above sheet, stretching and air-cooling shaping are performed to obtain the semi-finished POF heat shrink film;

[0030] (5) Cleaning: The semi-finished POF heat shrink film is cleaned with anhydrous ethanol and deionized water in sequence and then dried;

[0031] (6) Plasma activation: Using a plasma etching machine, plasma is selected to bombard the surface of the POF heat shrink film to activate its surface, increase the surface roughness of the POF heat shrink film and introduce new functional groups.

[0032] (7) PTFE coating: PTFE target material is deposited onto the surface of the activated PP film using a magnetron sputtering instrument;

[0033] (8) Finished product roll: The finished POF heat shrink film coated with PTFE layer is rolled into a film.

[0034] Preferably, in step (2), the melt blending temperature of the inner layer mixture is 160℃~165℃, and the melt blending temperature of the outer layer mixture is 150℃~160℃.

[0035] Preferably, in step (4), the preheating temperature is 180℃~200℃, the stretching is transverse stretching with a stretching ratio of 3-4 times, and the air-cooling shaping temperature is 20℃~30℃.

[0036] Preferably, in step (6), the activation time is 3-7 min and the gas flow rate is 40-50 sccm.

[0037] Preferably, in step (8), the thickness of the PTFE layer does not exceed 1 μm.

[0038] The POF heat-shrinkable film prepared using the above technical solution exhibits excellent wave absorption performance and superhydrophobic anti-icing properties when the film thickness does not exceed 300 μm. When the modified PET film layer thickness is 250 μm and a 70% concentration of ferromagnetic absorber is used, the effective bandwidth of the POF heat-shrinkable film ≤-4dB exceeds 6.5 GHz; when the PP film layer thickness is 20 μm, its surface is activated using CF4 high-energy particles, and a 0.8 μm PTFE layer is deposited, the water contact angle reaches 152.3°, achieving superhydrophobic functionality. Simultaneously, the POF heat-shrinkable film of this invention has a transverse shrinkage rate exceeding 75% and a longitudinal shrinkage rate less than 3%, demonstrating excellent heat-shrinkable performance.

[0039] The present invention also provides the application of the superhydrophobic anti-icing POF heat shrinkable film with wave absorption function on wind turbine blades.

[0040] The POF heat-shrinkable film prepared by this invention has excellent heat shrinkage properties, superhydrophobicity, and wave absorption function. When used as an outer covering material for wind turbine blades, it can protect the wind turbine blades in all aspects. It can not only improve the working efficiency and safety of wind turbine blades in harsh environments, but also effectively reduce the scattering intensity of radar waves by wind turbine blades and reduce the occurrence of icing, thereby improving the accuracy of radar systems and extending the service life of wind turbine blades.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] (1) This invention modifies the PET film by physical blending, reduces the crystallinity of the PET resin, and increases its heat shrinkage rate, so that the heat shrinkage rate of a single PET layer exceeds 80%. At the same time, absorbent is incorporated into the PET raw material, so that the modified PET film has the function of absorbing waves. High-energy particles are used to perform plasma etching on the surface of the PP film to improve the surface roughness of the film and introduce new functional groups, thereby increasing the adhesion of the PTFE layer. Meanwhile, by depositing an appropriate amount of PTFE target material on the surface of the PP film, the water contact angle of the POF heat shrink film surface is greatly increased, forming a superhydrophobic layer with a water contact angle of over 150°, which fundamentally solves the problem of easy icing on the outer surface of wind turbine blades.

[0043] (2) The POF heat shrink film of the present invention has a three-layer structure, with a modified PET film with wave absorption function as the inner layer and a PP film with PTFE layer as the two outer layers, so that the POF heat shrink film has wave absorption function and superhydrophobic anti-icing properties. When it is wrapped on the outer surface of the wind turbine blade, it can not only reduce the scattering intensity of radar waves by the wind turbine blade, improve the service life of the radar receiving device and avoid the risk of being burned, but also use a PP film with stable structure, excellent heat shrink performance and weather resistance as the outer layer to protect the PET layer with wave absorption function, which can meet the needs of wind turbine blades for long-term outdoor use.

[0044] (3) The POF heat-shrinkable film prepared by this invention exhibits excellent wave absorption performance and superhydrophobic anti-icing properties when the film thickness does not exceed 300 μm. When the modified PET film layer thickness is 250 μm and a 70% concentration of ferromagnetic absorber is used, the effective bandwidth of the POF heat-shrinkable film ≤-4dB exceeds 6.5 GHz; when the PP film layer thickness is 20 μm, and its surface is activated by CF4 high-energy particles and coated with a 0.8 μm PTFE layer, the water contact angle reaches 152.3°, achieving superhydrophobic functionality. Simultaneously, the POF heat-shrinkable film has a transverse shrinkage rate exceeding 75% and a longitudinal shrinkage rate less than 3%, demonstrating excellent heat-shrinkable performance. Attached Figure Description

[0045] The present invention will be further described below with reference to the accompanying drawings:

[0046] Figure 1 This is a front view of the POF heat-shrinkable film of the present invention;

[0047] In the diagram, PTFE coating 1, PP outer layer 2, and PET inner layer 3;

[0048] Figure 2 This is a water contact angle diagram of the POF heat-shrinkable film prepared in Example 1 of the present invention;

[0049] In the figure, (A) is a POF semi-finished film, (B) is the surface of a PP film after CF4 activation, and (C) is a POF finished film.

[0050] Figure 3 This is a water contact angle diagram of the POF heat-shrinkable film prepared in Example 2 of the present invention;

[0051] In the figure, (A) is a POF semi-finished film, (B) is the surface of a PP film after O2 activation, and (C) is a POF finished film. Detailed Implementation

[0052] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention.

[0053] Figure 1 The superhydrophobic anti-icing POF heat shrinkable film with wave absorption function of the present invention includes a PP outer layer 2, a PET inner layer 3 and a PP outer layer 2 stacked in sequence. The PET inner layer is a modified PET film with wave absorption function, and the PP outer layer is a PP film with a PTFE coating 3.

[0054] Example 1:

[0055] A superhydrophobic anti-icing POF heat-shrinkable film with wave-absorbing function includes an inner layer of modified PET film with wave-absorbing function and two outer layers of PP film coated with PTFE layer; wherein, the thickness of the inner PET film is 250μm, the thickness of the outer PP film is 20μm, the surface of the PP film is activated by CF4 high-energy particles, and the PTFE coating is deposited by magnetron sputtering with a thickness of 0.8μm;

[0056] The modified PET film comprises the following raw materials in weight percentage: 70% ferromagnetic metal absorber filler, 5% silica, 1% iron oxide, 10% PET, 10% PBT, 0.8% DOP, 0.5% glyceryl trioleate ester additive, 1% organotin heat stabilizer, 0.8% silica, and 0.9% salicylates.

[0057] The preparation method of the superhydrophobic anti-icing POF heat-shrinkable film with wave-absorbing function includes the following steps:

[0058] (1) Mixing: Weigh the raw materials for the outer and inner layers according to the proportions and mix them evenly;

[0059] (2) Feeding: The inner layer mixture is added to the first extruder, and the two sets of outer layer mixtures are added to the second and third extruders. After melt blending, the outer layer melt resin and the inner layer melt resin are obtained respectively. The melt blending temperature of the inner layer mixture is set to 160℃ and the melt blending temperature of the outer layer mixture is set to 155℃.

[0060] (3) Extruded sheet: The inner and outer molten resins extruded by the extruder pass through the metering pump and filter in sequence, and finally converge at the three-layer die head to extrude sheet-like melt, which is then cooled on the casting roller to form an unstretched sheet.

[0061] (4) Stretching and shaping: After preheating the above sheet at 190°C, stretch it transversely by 3 times and air-cool it at 25°C to obtain a semi-finished POF heat shrink film.

[0062] (5) Cleaning: First, use anhydrous ethanol to clean both sides of the PP layer of the semi-finished POF heat shrink film to remove oil and impurities; then clean it twice with deionized water and dry it with low temperature blower.

[0063] (6) Plasma activation: Using a plasma etching machine, CF4 plasma is selected to bombard the surface of the above-mentioned POF heat shrink film to activate its surface, increase the surface roughness of the POF heat shrink film and introduce new functional groups.

[0064] (7) PTFE coating: PTFE target material is deposited onto the surface of PP layer after plasma activation using a magnetron sputtering instrument. The activation time is about 5 minutes and the gas flow rate is 45 sccm.

[0065] (8) Finished product roll: The finished POF heat shrink film coated with PTFE layer is rolled into a film.

[0066] Figure 2 The diagram shows the water contact angle of the POF heat shrink film prepared in this embodiment. When CF4 is used as a high-energy particle to bombard the surface of the PP layer, low surface energy fluorine-containing groups such as -CF2 and -CF3 are introduced into the surface of the PP layer. After surface activation, the water contact angle of the POF heat shrink film increases from 87.8° to 103.2°, which enhances the hydrophobicity of the POF heat shrink film.

[0067] Example 2:

[0068] A superhydrophobic anti-icing POF heat-shrinkable film with wave-absorbing function includes a modified PET film layer with wave-absorbing function and two outer PP films coated with PTFE layer; wherein, the thickness of the inner PET film is 250μm, the thickness of the two outer PP films is 20μm, the surface of the PP film is activated by O2 high-energy particles, and the PTFE coating layer coated by magnetron sputtering has a thickness of 0.8μm;

[0069] The modified PET film comprises the following raw materials in weight percentage: 70% ferromagnetic metal absorber, 5% silica, 1% iron oxide, 10% PET, 10% PBT, 0.8% DOP, 0.5% glyceryl trioleate ester additive, 1% organotin heat stabilizer, 0.8% silica, and 0.9% salicylates.

[0070] The preparation method of the superhydrophobic anti-icing POF heat-shrinkable film with wave-absorbing function includes the following steps:

[0071] (1) Mixing: Weigh the raw materials for the outer and inner layers according to the proportions and mix them evenly;

[0072] (2) Feeding: The inner layer mixture is added to the first extruder, and the two sets of outer layer mixtures are added to the second and third extruders. After melt blending, the outer layer melt resin and the inner layer melt resin are obtained respectively. The melt blending temperature of the inner layer mixture is set to 160℃ and the melt blending temperature of the outer layer mixture is set to 155℃.

[0073] (3) Extruded sheet: The inner and outer molten resins extruded by the extruder pass through the metering pump and filter in sequence, and finally converge at the three-layer die head to extrude sheet-like melt, which is then cooled on the casting roller to form an unstretched sheet.

[0074] (4) Stretching and shaping: After preheating the above sheet at 190°C, stretch it transversely by 3 times and air-cool it at 25°C to obtain a semi-finished POF heat shrink film.

[0075] (5) Cleaning: First, use anhydrous ethanol to clean both sides of the PP layer of the semi-finished POF heat shrink film to remove oil and impurities; then clean it twice with deionized water and dry it with low temperature blower.

[0076] (6) Plasma activation: Using a plasma etching machine, select O2 plasma to bombard the surface of the above-mentioned POF heat shrink film to activate its surface, increase the surface roughness of the POF heat shrink film and introduce new functional groups.

[0077] (7) PTFE coating: PTFE target material is deposited onto the surface of PP layer after plasma activation using a magnetron sputtering instrument. The activation time is about 5 minutes and the gas flow rate is 45 sccm.

[0078] (8) Finished product roll: The finished POF heat shrink film coated with PTFE layer is rolled into a film.

[0079] Figure 3The diagram shows the water contact angle of the POF heat shrink film prepared in this embodiment. When O2 is used as a high-energy particle to bombard the surface of the PP film, a large number of hydrophilic groups such as -OH and -COOH are introduced into the surface of the PP film. After surface activation, the water contact angle value of the POF heat shrink film surface decreases from 87.4° to 36.7°, reducing the hydrophobicity of the POF heat shrink film.

[0080] Example 3:

[0081] A superhydrophobic anti-icing POF heat-shrinkable film with wave-absorbing function includes a modified PET film middle layer with wave-absorbing function and two PP film side layers coated with PTFE layer; wherein, the thickness of the middle PET film is 250μm, the thickness of the two PP film side layers is 20μm, the PP film surface is activated by CF4 high-energy particles, and the PTFE coating is deposited by magnetron sputtering with a thickness of 0.2μm.

[0082] The modified PET film comprises the following raw materials in weight percentage: 60% ferromagnetic metal absorber, 4% silica, 2% titanium dioxide, 20% PET, 10% PBT, 0.8% DOP, 0.5% glyceryl trioleate ester additive, 1% organotin heat stabilizer, 0.8% silica, and 0.9% xylene ketones.

[0083] The preparation method of the superhydrophobic anti-icing POF heat-shrinkable film with wave-absorbing function includes the following steps:

[0084] (1) Mixing: Weigh the raw materials for the outer and inner layers according to the proportions and mix them evenly;

[0085] (2) Feeding: The inner layer mixture is added to the first extruder, and the two sets of outer layer mixtures are added to the second and third extruders. After melt blending, the outer layer melt resin and the inner layer melt resin are obtained respectively. The melt blending temperature of the inner layer mixture is set to 165℃ and the blending temperature of the outer layer melt mixture is set to 155℃.

[0086] (3) Extruded sheet: The inner and outer molten resins extruded by the extruder pass through the metering pump and filter in sequence, and finally converge at the three-layer die head to extrude sheet-like melt, which is then cooled on the casting roller to form an unstretched sheet.

[0087] (4) Stretching and shaping: After preheating the above sheet at 185°C, stretch it transversely by 3 times and air-cool it at 25°C to obtain a semi-finished POF heat shrink film.

[0088] (5) Cleaning: First, use anhydrous ethanol to clean both sides of the PP layer of the semi-finished POF heat shrink film to remove oil and impurities; then clean it twice with deionized water and dry it with low temperature blower.

[0089] (6) Plasma activation: Using a plasma etching machine, CF4 plasma is selected to bombard the surface of the above-mentioned POF heat shrink film to activate its surface, increase the surface roughness of the POF heat shrink film and introduce new functional groups.

[0090] (7) PTFE coating: PTFE target material is deposited onto the surface of PP layer after plasma activation using a magnetron sputtering instrument. The activation time is about 5 minutes and the gas flow rate is 45 sccm.

[0091] (8) Finished product roll: The finished POF heat shrink film coated with PTFE layer is rolled into a film.

[0092] Example 4:

[0093] A superhydrophobic anti-icing POF heat-shrinkable film with wave-absorbing function includes a modified PET film middle layer with wave-absorbing function and two PP film side layers coated with PTFE layer; wherein, the thickness of the middle PET film is 250μm, the thickness of the two PP film side layers is 20μm, the PP film surface is activated by CF4 high-energy particles, and the PTFE coating is deposited by magnetron sputtering with a thickness of 0.8μm.

[0094] The modified PET film comprises the following raw materials by weight percentage: 50% light carbon-based absorbent, 7% silica, 3% titanium dioxide, 20% PET, 15% PBT, 1% DOP, 1% DEP, 1.2% organotin heat stabilizer, 0.8% erucamide, and 0.8% salicylates.

[0095] The preparation method of the superhydrophobic anti-icing POF heat-shrinkable film with wave-absorbing function includes the following steps:

[0096] (1) Mixing: Weigh the raw materials for the outer and inner layers according to the proportions and mix them evenly;

[0097] (2) Feeding: The inner layer mixture is added to the first extruder, and the two sets of outer layer mixtures are added to the second and third extruders. After melt blending, the outer layer melt resin and the inner layer melt resin are obtained respectively. The melt blending temperature of the inner layer mixture is set to 165℃ and the melt blending temperature of the outer layer mixture is set to 155℃.

[0098] (3) Extruded sheet: The inner and outer molten resins extruded by the extruder pass through the metering pump and filter in sequence, and finally converge at the three-layer die head to extrude sheet-like melt, which is then cooled on the casting roller to form an unstretched sheet.

[0099] (4) Stretching and shaping: After preheating the above sheet at 195°C, stretch it transversely by 3 times and air-cool it at 25°C to obtain a semi-finished POF heat shrink film.

[0100] (5) Cleaning: First, use anhydrous ethanol to clean both sides of the PP layer of the semi-finished POF heat shrink film to remove oil and impurities; then clean it twice with deionized water and dry it with low temperature blower.

[0101] (6) Plasma activation: Using a plasma etching machine, select O2 plasma to bombard the surface of the above-mentioned POF heat shrink film to activate its surface, increase the surface roughness of the POF heat shrink film and introduce new functional groups.

[0102] (7) PTFE coating: PTFE target material is deposited onto the surface of PP layer after plasma activation using a magnetron sputtering instrument. The activation time is about 5 minutes and the gas flow rate is 45 sccm.

[0103] (8) Finished product roll: The finished POF heat shrink film coated with PTFE layer is rolled into a film.

[0104] Comparative Example 1:

[0105] This comparative example is basically the same as Example 1, except that an unmodified PET film is used.

[0106] Comparative Example 2:

[0107] This comparative example is basically the same as Example 1, except that a PET film without absorbent is used.

[0108] Comparative Example 3:

[0109] This comparative example is basically the same as Example 1, except that the surface of the semi-finished POF heat shrink film is not coated with a PTFE layer.

[0110] The POF heat-shrinkable films prepared in Examples 1-4 and Comparative Examples 1-3 were tested for their microwave absorption performance, water contact angle, and heat shrinkage rate. The specific test methods are as follows:

[0111] (1) Test method for heat shrinkage rate:

[0112] Cut a 300mm × 300mm piece of POF heat shrink film and place it in an 85℃ oven for 180 seconds to allow it to shrink completely. After removing it, observe the dimensional changes of the POF heat shrink film and calculate the shrinkage rate of the POF heat shrink film in both the transverse and longitudinal directions.

[0113] (2) Water contact angle test method:

[0114] Cut a 50mm×50mm piece of POF heat shrink film, drop a water droplet with a diameter of about 0.5mm onto the film surface at room temperature, and use an SL 200C contact angle tester to measure the water contact angle of the POF heat shrink film surface.

[0115] (3) Wave absorption performance test method:

[0116] The N5224A microwave vector network analyzer was used to conduct the tests in a microwave anechoic chamber in accordance with the specifications of GJB 2038A-2011.

[0117] The test results are shown in Table 1.

[0118] Table 1. Performance test results of POF heat shrink films from the examples and comparative examples.

[0119]

[0120] As can be seen from Examples 1 and 3, when the PTFE layer thickness increases from 0.2 μm to 0.8 μm, the water contact angle increases from 121.7° to 152.3°. This means that the water contact angle, i.e., the anti-icing efficiency, on the surface of the POF heat-shrinkable film can be changed by adjusting the thickness of the magnetron sputtered PTFE layer. As can be seen from Examples 1 and 3-4, when filled with 70% ferromagnetic absorber, the effective absorption bandwidth of the POF heat-shrinkable film (≤-4.0 dB) exceeds 6.5 GHz. This means that the absorption performance of the POF heat-shrinkable film, including the effective absorption bandwidth and absorption peak position, can be changed by adjusting the type and concentration of the absorber in the PET film. As can be seen from Examples 1-4, the longitudinal heat shrinkage rate of the finished POF heat-shrinkable film does not exceed 3%, while the transverse heat shrinkage rate varies from 75.6% to 80.5% depending on parameters such as film thickness, coating thickness, type of plasma activation, and type and concentration of absorber.

[0121] As can be seen from Example 1 and Comparative Examples 1-3, using unmodified PET film reduces the heat shrinkage rate of POF heat shrink film; using modified PET film without added absorbent results in a smaller effective absorption bandwidth and poorer microwave absorption performance of POF heat shrink film; and the absence of a PTFE layer on the surface of the POF heat shrink film leads to a smaller water contact angle and poorer hydrophobicity. In Example 1, by selecting a suitable PTFE layer thickness, absorbent, and plasma type, a POF heat shrink film with superior microwave absorption, anti-icing, and heat shrinkage rate was prepared.

[0122] This invention optimizes the amount of each raw material by adjusting the thickness of the PTFE layer, the type and concentration of the absorbent, and the type of plasma. It achieves synergy in the types and amounts of each raw material, and prepares a POF heat-shrinkable film that simultaneously takes into account wave absorption function, anti-icing properties, and heat shrinkage rate. By using a three-layer POF heat-shrinkable film with a total thickness of no more than 300 μm, the water contact angle on the outer surface of the wind turbine blade exceeds 150° and has excellent wave absorption performance, thus solving the shortcomings of wind turbine blades such as lack of anti-icing and wave absorption function.

[0123] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A superhydrophobic anti-icing POF heat-shrinkable film with wave-absorbing function, characterized in that: The POF heat-shrinkable film comprises a PP outer layer, a PET inner layer, and another PP outer layer stacked sequentially, with a thickness of 290-300 μm. The PET inner layer is a modified PET film with microwave absorption function, comprising the following raw materials by weight percentage: 50%-70% absorbent filler, 5%-10% pigment, 20%-35% resin granules, and 1%-5% additives. The PP outer layer is a PP film with a PTFE coating, the thickness of which does not exceed 25 μm, and the thickness of the PTFE coating does not exceed 1 μm. The PTFE coating is prepared by radio frequency magnetron sputtering of a PTFE target. The absorbent filler includes one or more of ferromagnetic absorbers, carbon-based absorbers, or semiconductor absorbers. The pigment includes one or more of silica and metal oxides. The resin granules include one or more of PET and PBT. The additives include one or more of plasticizers, stabilizers, opening slip agents, and UV stabilizers.

2. The method for preparing the superhydrophobic anti-icing POF heat-shrinkable film with wave-absorbing function as described in claim 1, characterized in that: Includes the following steps: (1) Mixing: Weigh the raw materials for the outer and inner layers according to the proportions and mix them evenly; (2) Feeding: The inner layer mixture is added to the first extruder, and the two sets of outer layer mixtures are added to the second and third extruders. After melt blending, the outer layer melt resin and the inner layer melt resin are obtained respectively. (3) Extruded sheet: The inner and outer molten resins extruded by the extruder converge at the three-layer die head to extrude sheet-like melt, which is then cooled on the casting roller to form an unstretched sheet; (4) Stretching and shaping: After preheating the above sheet, stretching and air-cooling shaping are performed to obtain the semi-finished POF heat shrink film; (5) Cleaning: The semi-finished POF heat shrink film is cleaned with anhydrous ethanol and deionized water in sequence and then dried; (6) Plasma activation: Using a plasma etching machine, plasma is selected to bombard the surface of the POF heat shrink film to activate its surface, increase the surface roughness of the POF heat shrink film and introduce new functional groups. (7) PTFE coating: PTFE target material is deposited onto the surface of the activated PP film using a magnetron sputtering instrument; (8) Finished product roll: The finished POF heat shrink film coated with PTFE layer is rolled into a film.

3. The method for preparing the superhydrophobic anti-icing POF heat-shrinkable film with wave-absorbing function according to claim 2, characterized in that: In step (2), the melt blending temperature of the inner layer mixture is 160℃~165℃, and the melt blending temperature of the outer layer mixture is 150℃~160℃.

4. The method for preparing the superhydrophobic anti-icing POF heat-shrinkable film with wave-absorbing function according to claim 2, characterized in that: In step (4), the preheating temperature is 180℃~200℃, the stretching ratio is 3-4 times, and the air-cooling setting temperature is 20℃-30℃.

5. The application of the superhydrophobic anti-icing POF heat shrinkable film with wave absorption function as described in claim 1 on wind turbine blades.

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