Super-hydrophobic anti-icing POF heat shrink film with wave absorbing function and preparation method of super-hydrophobic anti-icing POF heat shrink film

Abstract

The invention provides a super-hydrophobic anti-icing POF heat shrinkage film with a wave absorbing function and a preparation method of the super-hydrophobic anti-icing POF heat shrinkage film. The POF heat shrinkage film comprises two PP outer layers and a PET inner layer, the PET inner layer is a modified PET film and comprises the following raw materials in percentage by weight: 50%-70% of absorbent filler, 5%-10% of pigment, 20%-35% of resin granules and 1%-5% of auxiliaries. According to the POF heat shrinkage film, PTFE layer plating treatment is conducted on the surface of the POF heat shrinkage film, a super-hydrophobic layer with the water contact angle exceeding 150 degrees is formed, and the problem that the outer surface of a wind power blade is prone to icing is fundamentally solved; by modifying the PET film, the thermal shrinkage rate of the PET film is improved, and meanwhile, the wave-absorbing material is introduced into the PET inner layer, so that the POF thermal shrinkage film has a wave-absorbing function. The prepared POF heat shrinkage film has excellent heat shrinkage performance, super-hydrophobic anti-icing performance and wave absorbing function, the outer surface of a wind power blade is coated with the POF heat shrinkage film, the scattering intensity of the wind power blade to radar waves is effectively reduced, the service life of a radar receiving device is prolonged, and the risk of burning loss is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of functional polyester heat shrinkable films, and in particular to a super hydrophobic anti-icing POF heat shrinkable film with a wave absorbing function and a preparation method thereof. Background Art

[0002] In response to global climate change, the Chinese government has proposed two-stage goals: "carbon peak" and "carbon neutrality". "Carbon peak" means that by 2030, greenhouse gas emissions from fossil fuel combustion activities such as coal, oil, and natural gas, industrial production processes, and land use changes and forestry activities will no longer increase and reach a peak. Wind energy is very popular as a clean renewable energy source. The wind energy reserves that can be developed in China exceed 1 billion kilowatts. Using wind turbines to convert wind energy into mechanical energy and then into electrical energy can avoid greenhouse gases such as carbon dioxide generated by fossil fuel power generation. Pollution to the environment. However, in winter, especially in coastal areas, wind turbine blades are prone to ice, which increases the weight of the blades and reduces their efficiency, thereby restricting the expansion of the wind power market.

[0003] Mechanical deicing, heating deicing and spraying of anti-icing coatings are the main deicing methods at present. Among them, mechanical deicing is the most commonly used method. This method is simple to operate, but it needs to be carried out after the equipment is shut down. On the one hand, it affects the power generation, and on the other hand, it consumes a lot of manpower and material resources. Heating deicing refers to connecting a resistor inside or outside the blade. After power is turned on, the resistor generates heat and melts the ice layer condensed on the surface of the blade. Although this method can save labor costs, it consumes a lot of electricity. In addition, both mechanical deicing and heating deicing will cause the blades to continue to freeze, and it is impossible to fundamentally prevent the occurrence of this phenomenon. The anti-icing coating sprayed on the blade surface is often a super-hydrophobic coating with low surface energy. Although this coating can prevent the condensation of ice and snow, the bonding strength between the coating and the surface of the wind turbine blade is weak, and it is easy to fall off and age.

[0004] In addition to the above three de-icing methods, studies have also shown that POF heat shrink film can be used to wrap the outer surface of wind turbine blades to enhance the anti-icing performance and anti-ultraviolet aging performance of wind turbine blades. The principle of POF heat shrink film is to force the polymer to be stretched in the longitudinal and transverse directions or in one direction between the glass transition temperature and the viscosity flow temperature, so that the polymer molecular chain is oriented along the stretching direction, and then the polymer is rapidly cooled to freeze the molecular orientation. When the film is reheated to the "thawing" temperature, the molecular chain relaxes and produces relative movement, and the molecules return to their original state and shrink. Commonly used heat shrink films include PVC heat shrink film, PE heat shrink film, etc. Among them, although the PVC heat shrink film has a large shrinkage rate, it is not environmentally friendly due to the presence of toxic vinyl chloride monomers; PE heat shrink film is relatively brittle and easy to crack and deform. Moreover, the use of these heat shrink films alone cannot solve the anti-icing problem.

[0005] In addition, ships equipped with radar transmitting and receiving devices often appear in coastal areas, especially in military waters. The special shape, material and rotation characteristics of wind turbine blades make them a strong scattering source of radar signals, reflecting the emitted radar waves back to the receiving device, thereby interfering with the radar signal and even burning 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 shrinkage, anti-icing, wave absorption and construction properties to meet the use requirements of wind turbine blades. Summary of the invention

[0007] In order to address the deficiencies in the prior art, the main purpose of the present invention is to provide a super hydrophobic anti-icing POF heat shrinkable film with wave absorbing function and a preparation method thereof. The POF heat shrinkable film of the present invention not only has good heat shrinkage and anti-icing properties, but also has a wave absorbing function. Coating it on the outer surface of a wind turbine blade can effectively reduce the scattering intensity of the wind turbine blade to radar waves, thereby increasing the service life of the radar receiving device and avoiding the risk of burning.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is: A super-hydrophobic anti-icing POF heat shrinkable film with a wave absorbing function, wherein the structure of the POF heat shrinkable film comprises a PP outer layer, a PET inner layer and a PP outer layer which are stacked in sequence, wherein the PET inner layer is a modified PET film with a wave absorbing function, and the PP outer layer is a PP film with a PTFE coating.

[0009] Preferably, the thickness of the POF heat shrinkable film does not exceed 300 μm.

[0010] 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.

[0011] Preferably, the modified PET film is modified by physical blending or graft copolymerization, aiming to reduce its crystallinity and increase its thermal shrinkage.

[0012] Preferably, the modified PET film comprises the following raw materials in weight percentage: 50% to 70% absorbent filler, 5% to 10% pigment, 20% to 35% resin pellets and 1% to 5% additives.

[0013] Preferably, the absorbent filler comprises one or more of a ferromagnetic absorbent, a carbon-based absorbent or a semiconductor absorbent; The pigment includes one or more of white carbon black and metal oxides; The resin pellets include one or more of PET and PBT; The auxiliary agent includes one or more of a plasticizer, a stabilizer, an opening lubricant, and an anti-ultraviolet agent.

[0014] More preferably, the plasticizer includes one or more of DOP, DEP, glyceryl trilinoleate, etc.; The stabilizer is mainly a heat stabilizer, including one or more of metal soaps, phosphates, and organotin; The opening lubricant includes one or more of erucamide and silicon dioxide; The anti-ultraviolet agent includes one or more ultraviolet absorbers such as salicylates, xylene ketones, benzotriazoles, and ultraviolet rating agents such as titanium dioxide, zinc oxide, talcum powder, and carbon black.

[0015] Preferably, the PTFE coating is prepared by radio frequency magnetron sputtering of a PTFE target.

[0016] More preferably, before preparing the PTFE coating, plasma gas is used to impact the surface of the PP film to activate it, increase the surface roughness of the film and introduce new groups, thereby enhancing the adhesion of the PTFE layer.

[0017] Preferably, the plasma gas is one or more of CF4 or O2.

[0018] The present invention also provides a method for preparing the super-hydrophobic anti-icing POF heat shrinkable film with wave absorbing function, comprising the following steps: (1) Mixing: weigh the raw materials for the outer layer and the inner layer according to the ratio and mix them evenly; (2) Feeding: adding the mixed material of the inner layer to the first extruder, and adding the mixed materials of the two groups of outer layers to the second extruder and the third extruder, and melt blending them to obtain the outer layer molten resin and the inner layer molten resin respectively; (3) Extruded sheet: The inner and outer layers of molten resin extruded by the extruder are combined at the three-layer die head to extrude the melt into a sheet, which is then cooled on the casting roll to form an unstretched sheet; (4) Stretching and shaping: After preheating the sheet, the semi-finished POF heat shrinkable film is obtained by stretching and air cooling; (5) Cleaning: Clean the semi-finished POF heat shrinkable film with anhydrous ethanol and deionized water in turn and dry it; (6) Plasma activation: Use a plasma etcher to bombard the surface of the POF heat shrinkable film with plasma to activate the surface, increase the surface roughness of the POF heat shrinkable film and introduce new functional groups; (7) PTFE coating: using a magnetron sputtering apparatus, depositing a PTFE target material onto the surface of the activated PP film; (8) Finished product roll: The finished POF heat shrinkable film after coating with PTFE layer is rolled into film.

[0019] Preferably, in step (2), the melt blending temperature of the inner layer mixture is 160°C to 165°C, and the melt blending temperature of the outer layer mixture is 150°C to 160°C.

[0020] Preferably, in step (4), the preheating temperature is 180°C to 200°C, the stretching is transverse stretching, the stretching multiple is 3-4 times, and the air-cooling setting temperature is 20°C to 30°C.

[0021] Preferably, in step (6), the activation time is 3-7 min and the gas flow rate is 40-50 sccm.

[0022] Preferably, in step (8), the thickness of the PTFE layer does not exceed 1 μm.

[0023] The POF heat shrinkable film prepared by the above technical solution has excellent wave absorption performance and super hydrophobic anti-icing property when the film thickness does not exceed 300μm. When the thickness of the modified PET film layer is 250μm and a ferromagnetic absorber with a concentration of 70% is used, the effective bandwidth of the POF heat shrinkable film ≤-4dB exceeds 6.5GHz; when the thickness of the PP film layer is 20μm, CF4 high-energy particles are used to activate its surface and a 0.8μm PTFE layer is plated, the water contact is as high as 152.3°, achieving the super hydrophobic function. At the same time, the POF heat shrinkable film of the present invention has a transverse shrinkage rate of more than 75% and a longitudinal shrinkage rate of less than 3%, and has good heat shrinkage performance.

[0024] The present invention also provides application of the super-hydrophobic anti-icing POF heat shrinkable film with wave absorbing function on wind turbine blades.

[0025] The POF heat shrinkable film prepared by the present invention has excellent heat shrinkage performance, super hydrophobicity and wave absorbing function. It is used as the outer coating material of wind turbine blades to protect the wind turbine blades in all directions, which can not only improve the working efficiency and safety of the wind turbine blades in harsh environments, but also effectively reduce the scattering intensity of wind turbine blades to radar waves and reduce the occurrence of icing, thereby improving the accuracy of the radar system and extending the service life of the wind turbine blades.

[0026] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention modifies the PET film by physical blending to reduce the crystallinity of the PET resin and increase its heat shrinkage, so that the heat shrinkage of a single PET layer exceeds 80%. At the same time, an absorbent is doped into the PET raw material, so that the prepared modified PET film has a wave absorbing function; the surface of the PP film is plasma etched by high-energy particles to increase the roughness of the film surface and introduce new functional groups to increase the adhesion of the PTFE layer; at the same time, by depositing an appropriate amount of PTFE target material on the surface of the PP film, the water contact angle of the surface of the POF heat shrinkable film is greatly increased, forming a super-hydrophobic layer with a water contact angle exceeding 150°, which fundamentally solves the problem that the outer surface of the wind turbine blade is easy to freeze.

[0027] (2) The POF heat shrinkable film of the present invention has a three-layer structure, with a modified PET film with a wave-absorbing function as the inner layer and a PP film coated with a PTFE layer as two outer layers, so that the POF heat shrinkable film has a wave-absorbing function and super-hydrophobic and anti-icing properties. Wrapping it on the outer surface of a wind turbine blade can not only reduce the scattering intensity of the wind turbine blade to radar waves, increase the service life of the radar receiving device and avoid the risk of burning, but also use a PP film with a stable structure, excellent heat shrinkage performance and weather resistance as the outer layer to protect the PET layer with a wave-absorbing function, which can meet the needs of long-term outdoor use of wind turbine blades.

[0028] (3) The POF heat shrinkable film prepared by the present invention has excellent wave absorption performance and super hydrophobic anti-icing property when the film thickness does not exceed 300 μm. When the thickness of the modified PET film layer is 250 μm and a ferromagnetic absorber with a concentration of 70% is used, the effective bandwidth of the POF heat shrinkable film ≤-4dB exceeds 6.5 GHz; when the thickness of the PP film layer is 20 μm, CF4 high-energy particles are used to activate its surface and a 0.8 μm PTFE layer is plated, the water contact is as high as 152.3°, achieving a super hydrophobic function. At the same time, the lateral shrinkage rate of the POF heat shrinkable film exceeds 75%, while the longitudinal shrinkage rate is less than 3%, and it has excellent heat shrinkage performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention will be further described below in conjunction with the accompanying drawings: Figure 1 It is a front view of the POF heat shrinkable film of the present invention; In the figure, PTFE coating 1, PP outer layer 2, PET inner layer 3; Figure 2 is a water contact angle diagram of the POF heat shrinkable film prepared in Example 1 of the present invention; In the figure, (A) POF semi-finished film, (B) PP film surface after CF4 activation, (C) POF finished film; Figure 3 is a water contact angle diagram of the POF heat shrinkable film prepared in Example 2 of the present invention; In the figure, (A) POF semi-finished film, (B) PP film surface after O2 activation, (C) POF finished film. DETAILED DESCRIPTION

[0030] The embodiments of the present invention will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention.

[0031] Figure 1 The super-hydrophobic anti-icing POF heat shrinkable film with wave absorbing function of the present invention comprises a PP outer layer 2, a PET inner layer 3 and a PP outer layer 2 stacked in sequence, wherein the PET inner layer is a modified PET film with wave absorbing function, and the PP outer layer is a PP film with a PTFE coating 3.

[0032] Embodiment 1: A super-hydrophobic anti-icing POF heat shrinkable film with wave-absorbing function, comprising a modified PET film inner layer with wave-absorbing function and two PP film outer layers coated with PTFE layers; wherein the thickness of the inner PET film is 250 μm, the thickness of the outer PP film is 20 μm, the surface of the PP film is activated by CF4 high-energy particles, and the thickness of the PTFE coating coated by magnetron sputtering is 0.8 μm; The modified PET film comprises the following raw materials in weight percentage: 70% ferromagnetic metal absorbent filler, 5% white carbon black, 1% iron oxide, 10% PET, 10% PBT, 0.8% DOP, 0.5% glycerol trilinoleate additive, 1% organic tin heat stabilizer, 0.8% silicon dioxide, and 0.9% salicylate.

[0033] The method for preparing the super-hydrophobic anti-icing POF heat shrinkable film with wave absorbing function comprises the following steps: (1) Mixing: weigh the raw materials for the outer layer and the inner layer according to the ratio and mix them evenly; (2) Feeding: adding the mixed material of the inner layer to the first extruder, and adding the mixed materials of the two outer layers to the second extruder and the third extruder, and melt blending them to obtain the outer layer molten resin and the inner layer molten resin respectively. The melt blending temperature of the inner layer mixed material is set to 160° C., and the melt blending temperature of the outer layer mixed material is set to 155° C.; (3) Extruded sheet: The inner and outer molten resins extruded from the extruder pass through a metering pump and a filter in sequence, and finally converge at a three-layer die head to extrude a sheet of melt, which is then cooled on a casting roll to form an unstretched sheet. (4) Stretching and shaping: After preheating the sheet at 190° C., the sheet is stretched 3 times in the transverse direction and air-cooled at 25° C. to obtain a semi-finished POF heat shrinkable film; (5) Cleaning: First, use anhydrous ethanol to clean the PP layers on both sides of the semi-finished POF heat shrink film to remove oil stains and impurities; then wash it twice with deionized water and dry it with low-temperature air blast; (6) Plasma activation: using a plasma etcher, selecting CF4 plasma to bombard the surface of the POF heat shrinkable film to activate the surface, increase the surface roughness of the POF heat shrinkable film and introduce new functional groups; (7) PTFE coating: A magnetron sputtering apparatus is used to deposit a PTFE target onto the surface of the plasma activated PP layer, wherein the activation time is about 5 min and the gas flow rate is 45 sccm; (8) Finished product roll: The finished POF heat shrinkable film after coating with PTFE layer is rolled into film.

[0034] Figure 2 This is a graph of the water contact angle of the POF heat shrinkable 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 on the surface of the PP layer. After surface activation, the water contact angle on the surface of the POF heat shrinkable film increases from 87.8° to 103.2°, thereby enhancing the hydrophobicity of the POF heat shrinkable film.

[0035] Embodiment 2: A super-hydrophobic anti-icing POF heat shrinkable film with wave-absorbing function, comprising a modified PET film layer with wave-absorbing function and two outer PP films coated with PTFE layers; wherein the thickness of the inner PET film is 250 μm, the thickness of the two outer PP films is 20 μm, the surface of the PP film is activated by O2 high-energy particles, and the thickness of the PTFE coating coated by magnetron sputtering is 0.8 μm; The modified PET film comprises the following raw materials in weight percentage: 70% ferromagnetic metal absorber, 5% white carbon black, 1% iron oxide, 10% PET, 10% PBT, 0.8% DOP, 0.5% glycerol trilinoleate additive, 1% organic tin heat stabilizer, 0.8% silicon dioxide, and 0.9% salicylate.

[0036] The method for preparing the super-hydrophobic anti-icing POF heat shrinkable film with wave absorbing function comprises the following steps: (1) Mixing: weigh the raw materials for the outer layer and the inner layer according to the ratio and mix them evenly; (2) Feeding: adding the mixed material of the inner layer to the first extruder, and adding the mixed materials of the two outer layers to the second extruder and the third extruder, and melt blending them to obtain the outer layer molten resin and the inner layer molten resin respectively. The melt blending temperature of the inner layer mixed material is set to 160° C., and the melt blending temperature of the outer layer mixed material is set to 155° C.; (3) Extruded sheet: The inner and outer molten resins extruded from the extruder pass through a metering pump and a filter in sequence, and finally converge at a three-layer die head to extrude a sheet of melt, which is then cooled on a casting roll to form an unstretched sheet. (4) Stretching and shaping: After preheating the sheet at 190° C., the sheet is stretched 3 times in the transverse direction and air-cooled at 25° C. to obtain a semi-finished POF heat shrinkable film; (5) Cleaning: First, use anhydrous ethanol to clean the PP layers on both sides of the semi-finished POF heat shrink film to remove oil stains and impurities; then wash it twice with deionized water and dry it with low-temperature air blast; (6) Plasma activation: using a plasma etcher, selecting O2 plasma to bombard the surface of the POF heat shrinkable film to activate the surface, increase the surface roughness of the POF heat shrinkable film and introduce new functional groups; (7) PTFE coating: A magnetron sputtering apparatus is used to deposit a PTFE target onto the surface of the plasma activated PP layer, wherein the activation time is about 5 min and the gas flow rate is 45 sccm; (8) Finished product roll: The finished POF heat shrinkable film after coating with PTFE layer is rolled into film.

[0037] Figure 3 This is the water contact angle diagram of the POF heat shrinkable 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 on the surface of the PP film; after surface activation, the water contact angle value on the surface of the POF heat shrinkable film decreases from 87.4° to 36.7°, reducing the hydrophobicity of the POF heat shrinkable film.

[0038] Embodiment 3: A super-hydrophobic anti-icing POF heat shrinkable film with wave-absorbing function comprises a modified PET film middle layer with wave-absorbing function and two side layers of PP film coated with PTFE layer; wherein the thickness of the middle layer PET film is 250 μm, the thickness of the two side layers of PP film is 20 μm, CF4 high-energy particles are used to activate the surface of the PP film, and the thickness of the PTFE coating coated by magnetron sputtering is 0.2 μm.

[0039] The modified PET film includes the following raw materials in weight percentage: 60% ferromagnetic metal absorber, 4% white carbon black, 2% titanium dioxide, 20% PET, 10% PBT, 0.8% DOP, 0.5% glycerol trilinoleate additive, 1% organic tin heat stabilizer, 0.8% silicon dioxide, and 0.9% xylene ketone.

[0040] The method for preparing the super-hydrophobic anti-icing POF heat shrinkable film with wave absorbing function comprises the following steps: (1) Mixing: weigh the raw materials for the outer layer and the inner layer according to the ratio and mix them evenly; (2) Feeding: The mixed material of the inner layer is added to the first extruder, and the mixed materials of the two outer layers are added to the second extruder and the third extruder, and melt blended to obtain the outer layer molten resin and the inner layer molten resin, respectively. The melt blending temperature of the inner layer mixed material is set to 165° C., and the blending temperature of the outer layer molten mixed material is set to 155° C.; (3) Extruded sheet: The inner and outer molten resins extruded from the extruder pass through a metering pump and a filter in sequence, and finally converge at a three-layer die head to extrude a sheet of melt, which is then cooled on a casting roll to form an unstretched sheet. (4) Stretching and shaping: After preheating the sheet at 185° C., the sheet is stretched 3 times in the transverse direction and air-cooled at 25° C. to obtain a semi-finished POF heat shrinkable film; (5) Cleaning: First, use anhydrous ethanol to clean the PP layers on both sides of the semi-finished POF heat shrink film to remove oil stains and impurities; then wash it twice with deionized water and dry it with low-temperature air blast; (6) Plasma activation: using a plasma etcher, selecting CF4 plasma to bombard the surface of the POF heat shrinkable film to activate the surface, increase the surface roughness of the POF heat shrinkable film and introduce new functional groups; (7) PTFE coating: A magnetron sputtering apparatus is used to deposit a PTFE target onto the surface of the plasma activated PP layer, wherein the activation time is about 5 min and the gas flow rate is 45 sccm; (8) Finished product roll: The finished POF heat shrinkable film after coating with PTFE layer is rolled into film.

[0041] Embodiment 4: A super-hydrophobic anti-icing POF heat shrinkable film with wave-absorbing function comprises a modified PET film middle layer with wave-absorbing function and two side layers of PP film coated with PTFE layer; wherein the thickness of the middle layer PET film is 250 μm, the thickness of the two side layers of PP film is 20 μm, CF4 high-energy particles are used to activate the surface of the PP film, and the thickness of the PTFE coating coated by magnetron sputtering is 0.8 μm.

[0042] The modified PET film includes the following raw materials in weight percentage: 50% light carbon-based absorbent, 7% white carbon black, 3% titanium dioxide, 20% PET, 15% PBT, 1% DOP, 1% DEP, 1.2% organotin heat stabilizer, 0.8% erucamide, and 0.8% salicylic acid ester.

[0043] The method for preparing the super-hydrophobic anti-icing POF heat shrinkable film with wave absorbing function comprises the following steps: (1) Mixing: weigh the raw materials for the outer layer and the inner layer according to the ratio and mix them evenly; (2) Feeding: The mixed material of the inner layer is added to the first extruder, and the mixed materials of the two outer layers are added to the second extruder and the third extruder, and melt blended to obtain the outer layer molten resin and the inner layer molten resin respectively. The melt blending temperature of the inner layer mixed material is set to 165° C., and the melt blending temperature of the outer layer mixed material is set to 155° C.; (3) Extruded sheet: The inner and outer molten resins extruded from the extruder pass through a metering pump and a filter in sequence, and finally converge at a three-layer die head to extrude a sheet of melt, which is then cooled on a casting roll to form an unstretched sheet. (4) Stretching and shaping: After preheating the sheet at 195° C., the sheet is stretched 3 times in the transverse direction and air-cooled at 25° C. to obtain a semi-finished POF heat shrinkable film; (5) Cleaning: First, use anhydrous ethanol to clean the PP layers on both sides of the semi-finished POF heat shrink film to remove oil stains and impurities; then wash it twice with deionized water and dry it with low-temperature air blast; (6) Plasma activation: using a plasma etcher, selecting O2 plasma to bombard the surface of the POF heat shrinkable film to activate the surface, increase the surface roughness of the POF heat shrinkable film and introduce new functional groups; (7) PTFE coating: A magnetron sputtering apparatus is used to deposit a PTFE target onto the surface of the plasma activated PP layer, wherein the activation time is about 5 min and the gas flow rate is 45 sccm; (8) Finished product roll: The finished POF heat shrinkable film after coating with PTFE layer is rolled into film.

[0044] Comparative Example 1: This comparative example is basically the same as Example 1, except that an unmodified PET film is used.

[0045] Comparative Example 2: This comparative example is basically the same as Example 1, except that a PET film without absorbent is used.

[0046] Comparative Example 3: This comparative example is basically the same as Example 1, except that the surface of the semi-finished POF heat shrinkable film is not coated with a PTFE layer.

[0047] The POF heat shrinkable films prepared in the above Examples 1-4 and Comparative Examples 1-3 were tested for wave absorption performance, water contact angle and heat shrinkage rate, respectively. The specific testing methods are as follows: (1) Thermal shrinkage test method: Cut a 300mm×300mm POF heat shrink film and place it in an 85℃ oven for 180s to complete shrinkage. After taking it out, observe the dimensional change of the POF heat shrink film and calculate the shrinkage rate of the POF heat shrink film in both the horizontal and vertical directions.

[0048] (2) Water contact angle test method: A 50 mm × 50 mm POF heat shrink film was cut and a water droplet with a diameter of about 0.5 mm was dropped on the film surface at room temperature. The water contact angle on the surface of the POF heat shrink film was tested using an SL 200C contact angle tester.

[0049] (3) Wave absorption performance test method: The test was carried out in a microwave darkroom using a N5224A microwave vector network analyzer in accordance with GJB 2038A-2011.

[0050] The test results are shown in Table 1.

[0051] Table 1 Performance test results of POF heat shrinkable films of embodiments and comparative examples

[0052] It can be seen from Example 1 and Example 3 that when the thickness of the PTFE layer is increased from 0.2μm to 0.8μm, the water contact angle value increases from 121.7° to 152.3°. That is, the water contact angle on the surface of the POF heat shrinkable film, that is, the anti-icing efficiency, can be changed by adjusting the thickness of the magnetron sputtered PTFE layer. It can be seen from Example 1 and Examples 3-4 that when 70% of the ferromagnetic absorber is filled, the effective absorption bandwidth of the POF heat shrinkable film ≤-4.0dB exceeds 6.5GHz; that is, the type and concentration of the absorber in the PET film can be adjusted to change the wave absorption performance of the POF heat shrinkable film, including the effective absorption bandwidth, wave absorption peak position, etc. It can be seen from Examples 1-4 that the longitudinal heat shrinkage rate of the finished POF heat shrinkable film does not exceed 3%, and the transverse heat shrinkage rate changes with the changes in parameters such as film thickness, coating thickness, plasma activation type, absorbent type and concentration, ranging from 75.6% to 80.5%.

[0053] It can be seen from Example 1 and Comparative Examples 1-3 that the heat shrinkage rate of the POF heat shrink film is reduced by using an unmodified PET film; the effective absorption bandwidth of the POF heat shrink film is small and the wave absorption performance is poor by using a modified PET film without adding an absorbent; the surface of the POF heat shrink film is not coated with a PTFE layer, the water contact angle of the heat shrink film is small and the hydrophobicity is poor. In Example 1, a PTFE layer of appropriate thickness, an absorbent and a plasma type are selected to prepare a POF heat shrink film with excellent wave absorption function, anti-icing property and heat shrinkage rate.

[0054] The present invention optimizes the amount of each raw material by adjusting the thickness of the PTFE layer, the type and concentration of the absorbent, the type of plasma, etc., and achieves mutual synergy in the type and amount of each raw material to prepare a POF heat shrinkable film that takes into account the wave absorbing function, anti-icing property and heat shrinkage rate. By adopting a three-layer POF heat shrinkable film with a total thickness of no more than 300 μm, the water contact angle of the outer surface of the wind turbine blade exceeds 150° and has excellent wave absorbing performance, thereby solving the disadvantages of the wind turbine blade not being anti-icing and not having the wave absorbing function.

[0055] The above embodiments are only preferred technical solutions of the present invention and should not be regarded as limiting the present invention. The protection scope of the present invention shall be the technical solutions recorded in the claims, including equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A super-hydrophobic 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 a PP outer layer which are stacked in sequence, the PET inner layer is a modified PET film with a wave absorbing function, and the PP outer layer is a PP film with a PTFE coating.

2. The super-hydrophobic anti-icing POF heat shrinkable film with wave absorbing function according to claim 1, characterized in that: The thickness of the POF heat shrinkable film does not exceed 300 μm.

3. The super-hydrophobic anti-icing POF heat shrinkable film with wave absorbing function according to claim 1, characterized in that: The thickness of the PP outer layer does not exceed 25 μm, and the thickness of the PTFE coating does not exceed 1 μm.

4. The super-hydrophobic anti-icing POF heat shrinkable film with wave absorbing function according to claim 1, characterized in that: The modified PET film comprises the following raw materials in weight percentage: 50% to 70% of absorbent filler, 5% to 10% of pigment, 20% to 35% of resin granules and 1% to 5% of auxiliary agent.

5. The super-hydrophobic anti-icing POF heat shrinkable film with wave absorbing function according to claim 1, characterized in that: The absorbent filler includes one or more of a ferromagnetic absorbent, a carbon-based absorbent, or a semiconductor absorbent; The pigment includes one or more of white carbon black and metal oxides; The resin pellets include one or more of PET and PBT; The auxiliary agent includes one or more of a plasticizer, a stabilizer, an opening lubricant, and an anti-ultraviolet agent.

6. The super-hydrophobic anti-icing POF heat shrinkable film with wave absorbing function according to claim 1, characterized in that: The PTFE coating is prepared by radio frequency magnetron sputtering of a PTFE target.

7. The method for preparing the super-hydrophobic anti-icing POF heat shrinkable film with wave absorbing function according to any one of claims 1 to 6, characterized in that: The steps include: (1) Mixing: weigh the raw materials for the outer layer and the inner layer according to the ratio and mix them evenly; (2) Feeding: adding the mixed material of the inner layer to the first extruder, and adding the mixed materials of the two groups of outer layers to the second extruder and the third extruder, and melt blending them to obtain the outer layer molten resin and the inner layer molten resin respectively; (3) Extruded sheet: The inner and outer layers of molten resin extruded by the extruder are combined at the three-layer die head to extrude the melt into a sheet, which is then cooled on the casting roll to form an unstretched sheet; (4) Stretching and shaping: After preheating the sheet, the semi-finished POF heat shrinkable film is obtained by stretching and air cooling; (5) Cleaning: Clean the semi-finished POF heat shrinkable film with anhydrous ethanol and deionized water in turn and dry it; (6) Plasma activation: Use a plasma etcher to bombard the surface of the POF heat shrinkable film with plasma to activate the surface, increase the surface roughness of the POF heat shrinkable film and introduce new functional groups; (7) PTFE coating: using a magnetron sputtering apparatus, depositing a PTFE target material onto the surface of the activated PP film; (8) Finished product roll: The finished POF heat shrinkable film after coating with PTFE layer is rolled into film.

8. The method for preparing the super-hydrophobic anti-icing POF heat shrinkable film with wave absorbing function according to claim 7, characterized in that: In step (2), the melt blending temperature of the inner layer mixture is 160°C to 165°C, and the melt blending temperature of the outer layer mixture is 150°C to 160°C.

9. The method for preparing the super-hydrophobic anti-icing POF heat shrinkable film with wave absorbing function according to claim 7, characterized in that: In step (4), the preheating temperature is 180°C-200°C, the stretching ratio is 3-4 times, and the air-cooling setting temperature is 20°C-30°C.

10. Application of the super hydrophobic anti-icing POF heat shrinkable film with wave absorbing function as claimed in any one of claims 1 to 6 on wind turbine blades.

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