A thermal insulation window film and a method of making the same

Abstract

The application relates to a heat-insulating window film and a preparation method thereof, which comprises a protective layer, a barrier layer, a pressure-sensitive adhesive layer and a release film layer, wherein the barrier layer comprises PET resin, a carbon nanotube composite, an epoxy resin, composite nanoparticles and a curing agent; the carbon nanotube composite comprises modified carbon nanotubes, polylactic acid and polybutylene adipate terephthalate. The application has the effect of improving the heat-insulating performance and strength of the window film.

Description

Technical Field

[0001] This application relates to the field of heat-insulating window films, and more particularly to a heat-insulating window film and a method for preparing the same. Background Technology

[0002] Window film is a multi-layered, multi-functional polyester composite optical-grade special film product. It is applied to the glass surface to improve the performance and strength of the glass, giving it functions such as explosion-proof, privacy protection, and safety protection.

[0003] When driving in hot weather, ordinary window film is insufficient to further block heat and infrared radiation. When sunlight shines on a person's skin, the skin temperature rises rapidly, causing increased moisture loss, making the skin dry and rough. Heat can also affect a person's concentration, so there is room for improvement. Summary of the Invention

[0004] To further improve the heat insulation performance of window film, this application provides a heat-insulating window film and its preparation method.

[0005] The technical solution for the heat-insulating window film and its preparation method provided in this application is as follows:

[0006] Firstly, this application provides a heat-insulating window film, which adopts the following technical solution:

[0007] A heat-insulating window film includes a protective layer, a barrier layer, a pressure-sensitive adhesive layer, and a release film layer. The barrier layer includes PET resin, carbon nanotube composite, epoxy resin, composite nanoparticles, and a curing agent. The carbon nanotube composite includes modified carbon nanotubes, polylactic acid, and polybutylene terephthalate.

[0008] By adopting the above technical solution, the carbon nanotube composite is prepared by modifying carbon nanotubes, polylactic acid, and polybutylene terephthalate. Carbon nanotubes are a unique nanostructure with good mechanical and thermal properties. They have high reflectivity in the infrared band and can absorb and scatter infrared rays, thereby blocking infrared rays and further achieving a heat insulation effect. Polylactic acid is a rigid polymer, and polybutylene terephthalate has good elasticity and excellent biodegradability. It can be combined and blended with polylactic acid. After being compounded with modified carbon nanotubes, a polymer composite material with balanced mechanical properties can be obtained. This results in a heat insulation film with good thermomechanical, chemical, and physical properties, further improving the overall strength and heat insulation performance of the prepared window film.

[0009] Preferably, the modified carbon nanotubes comprise carboxylated carbon nanotubes and polyethyleneimine.

[0010] By adopting the above technical solution, polyethyleneimine has a three-dimensional dendritic structure and is a flexible polymer rich in primary and secondary amine groups. When combined with carboxylated carbon nanotubes, it can improve the dispersion performance of carboxylated carbon nanotubes in the system and further combine with epoxy resin to enhance the overall stability of the system.

[0011] Preferably, the modified carbon nanotubes are prepared by the following method:

[0012] Polyethyleneimine was mixed with water to obtain a polyethyleneimine solution. Carboxylated carbon nanotubes were added to the polyethyleneimine solution to obtain a carbon nanotube dispersion. The carbon nanotube dispersion was refluxed in an oil bath, vacuum filtered, washed and dried to obtain modified carbon nanotubes.

[0013] By adopting the above technical solution, the amino groups of polyethyleneimine and the carboxyl groups of carboxylated carbon nanotubes undergo an amidation reaction to form amide bonds, thereby enabling polyethyleneimine to be grafted onto the surface of carboxylated carbon nanotubes. The dendritic polymer polyethyleneimine can effectively improve the dispersion effect of carboxylated carbon nanotubes in the system and can participate in the curing and crosslinking reaction of epoxy resin, further improving the interfacial bonding between carbon nanotubes and epoxy resin matrix, thus further enhancing the overall stability of the system.

[0014] Preferably, the carbon nanotube composite is prepared by the following method:

[0015] Polylactic acid, polybutylene terephthalate, and modified carbon nanotubes were mixed and stirred in a water bath to obtain a reactant. After melting, extrusion, and injection molding, a carbon nanotube composite was obtained.

[0016] Polybutylene terephthalate (PET) can induce nucleation, thereby increasing crystallinity and allowing the modified carbon nanotubes to be more uniformly dispersed in the system. This reduces the occurrence of defects in the system and further improves the overall stability of the system. As a result, the mechanical properties and stability of the prepared heat insulation film are improved.

[0017] Preferably, the mass ratio of polylactic acid, polybutylene terephthalate-adipate and modified carbon nanotubes is 3.5:1:(0.27-0.33).

[0018] By adopting the above technical solution, and optimizing the mass ratio of polylactic acid, polybutylene terephthalate-adipate and modified carbon nanotubes within the above range, the stability of the prepared modified carbon nanotubes can be further improved.

[0019] Preferably, the mass ratio of the carbon nanotube composite to the epoxy resin is 1:(4-5).

[0020] By adopting the above technical solution, and preferably within the above range the mass ratio of carbon nanotube composite to epoxy resin, the bonding performance and stability between the various components in the system can be further improved.

[0021] Preferably, the composite nanoparticles include silicon dioxide, titanium dioxide, and fluoroalkylsilane.

[0022] By adopting the above technical solution, titanium dioxide, an oxide with good chemical properties, good stability, and anti-fouling, self-cleaning, and anti-corrosion properties, is introduced as a carrier. This can further reduce the aggregation of titanium dioxide in the system and construct a nano-micro two-layer structure, reducing the proportion of wetted surfaces, increasing roughness, and further improving the overall hydrophobic properties of the system. However, it is easy to lose its hydrophobic properties under sunlight. After adding fluoroalkylsilane, it can hydrolyze and crosslink in the system to form a solid film and a catalyst-free self-healing additive, restoring the hydrophobic properties of the system under ultraviolet light, further improving the hydrophobic stability of the system. It can also synergistically fill the resin system with carbon nanotube composites to improve the system's bonding performance, thermal insulation performance, and mechanical strength.

[0023] Preferably, the composite nanoparticles are prepared by the following method:

[0024] Titanium sulfate was mixed with water, nano-titanium dioxide powder was added, the mixture was stirred and ammonia was added for hydrolysis to obtain a precipitate. The precipitate was filtered and washed, then dispersed in water and nitric acid was added to obtain a silica composite sol. After drying, the sol was calcined to obtain silica composite titanium dioxide. Anhydrous ethanol, toluene and fluoroalkylsilane were mixed and silica composite titanium dioxide was added. After ultrasonic dispersion, the mixture was centrifuged, washed and dried to obtain composite nanoparticles.

[0025] By adopting the above technical solution, using silica microspheres as a carrier, titanium dioxide is loaded onto silica via a hydrothermal method. The agglomeration of titanium dioxide is significantly improved. Due to the curvature of titanium dioxide and the presence of Ti-O-Si bonds, the further growth of titanium dioxide particles is inhibited, resulting in smaller particle diameters and uniform coating on the silica surface, forming micro-nano particles with a certain roughness. This also effectively improves the loading rate and enhances the overall stability of the prepared composite nanoparticles.

[0026] Preferably, the mass ratio of the composite nanoparticles to the carbon nanotube composite is (1.5-1.4):1.

[0027] By adopting the above technical solution, and preferably within the above range the mass ratio between composite nanoparticles and carbon nanotubes, the stability of the prepared window film can be further improved, and the dispersibility and mechanical properties of the window film can be synergistically enhanced.

[0028] Secondly, this application provides a method for preparing a heat-insulating window film, which adopts the following technical solution:

[0029] A method for preparing a heat-insulating window film includes the following steps:

[0030] PET resin, carbon nanotube composite, epoxy resin, and curing agent are mixed and stirred evenly. After intensive mixing, roughing and refining processes, the mixture is cooled and extruded, filtered, and then cooled and shaped after four-roll calendering, embossing and warm refining. The edges are then trimmed and rolled up to obtain a barrier layer. The protective layer, barrier layer, pressure-sensitive adhesive layer and release film layer are sequentially composited to prepare a heat-insulating window film.

[0031] In summary, this application includes at least one of the following beneficial technical effects:

[0032] 1. In this application, a carbon nanotube composite component is added to the system. This carbon nanotube composite component is prepared by combining carbon nanotubes, polylactic acid (PLA), and polybutylene terephthalate (PET). Carboxylated carbon nanotubes are a component with a unique nanostructure, possessing excellent mechanical properties and strength. They can absorb and dissipate infrared radiation, thus blocking infrared rays and providing good thermal insulation. PLA is a rigid polymer, and PET has good elasticity and excellent biodegradability. Furthermore, it can further combine with PLA to obtain a composite material with good mechanical properties. This results in a thermal insulation film with excellent thermal insulation performance and high mechanical strength.

[0033] 2. Modified carbon nanotubes are prepared by combining carboxylated carbon nanotubes with polyethyleneimine. Polyethyleneimine has a three-dimensional dendritic structure and is a flexible polymer rich in primary and secondary amine groups. When combined with carboxylated carbon nanotubes, it can further improve the dispersion performance of carboxylated carbon nanotubes in the system. At the same time, it can further combine with epoxy resin to form a stable system, which further enhances the overall performance of the prepared heat insulation film.

[0034] 3. Composite nanoparticles were also added to the system. Titanium dioxide was loaded onto silica using a hydrothermal method, which significantly improved the aggregation of silica, thereby enhancing the anti-corrosion and self-cleaning properties of the system. Then, it was modified with fluoroalkylsilane, which hydrolyzed and crosslinked in the system to form a solid film and additives with self-healing properties, resulting in a hydrophobic system and further improving the overall stability of the system. Detailed Implementation

[0035] The present application will be further described in detail below with reference to the embodiments:

[0036] Raw material description: All raw materials in the examples are commercially available; the curing agent is diethylenetriamine (CAS No.: 111-40-0).

[0037] Example 1

[0038] Preparation of modified carbon nanotubes:

[0039] 1.45 g of polyethyleneimine (CAS No.: 9002-98-6) was mixed with 500 g of deionized water to obtain a polyethyleneimine solution. 7.27 g of carboxylated carbon nanotubes (CAS No.: 308068-56-6) were added to the polyethyleneimine solution to obtain a carbon nanotube dispersion. The carbon nanotube dispersion was refluxed in an oil bath at 120 °C for 12 h, vacuum filtered, and then washed repeatedly with deionized water 5 times. Finally, it was freeze-dried in a vacuum freeze dryer at -20 °C for 18 h to obtain modified carbon nanotubes.

[0040] Preparation of carbon nanotube composites:

[0041] 29.35g of polylactic acid (CAS No.: 26023-30-3), 8.39g of polybutylene terephthalate (CAS No.: 55231-08-8), and 2.26g of modified carbon nanotubes were mixed and stirred under vacuum for 2 hours in a water bath at 25°C to obtain a reactant. The solvent was then evaporated in a fume hood, and the reactant was melted and extruded in a twin-screw extruder. After injection molding, the reactant was ground to obtain a carbon nanotube composite.

[0042] Preparation of composite nanoparticles:

[0043] 60g of titanium sulfate was mixed with 900g of deionized water, and then 6g of nano-titanium dioxide powder was added. The mixture was stirred at 25℃ while ammonia was added for hydrolysis until the pH of the system reached 7.5, resulting in a precipitate. The precipitate was filtered and washed with ethanol, then added to 500g of deionized water. 20wt% nitric acid was added until the pH of the system reached 2, thus preparing a silica composite sol. After drying at 45℃, the sol was calcined at 500℃ for 2 hours to obtain silica composite titanium dioxide. 90g of anhydrous ethanol, 90g of toluene, and 6g of perfluorooctyltriethoxysilane were mixed, and the pH of the system was adjusted to 9 with ammonia. Then, 18g of the prepared silica composite titanium dioxide was added. After ultrasonic dispersion, the mixture was centrifuged at 8000rpm for 10 minutes, washed, and dried at 65℃ for 8 hours to obtain composite nanoparticles.

[0044] Preparation of heat-insulating window film:

[0045] Acrylic pressure-sensitive adhesive is coated onto the surface of release paper and allowed to mature at 55°C. After drying, a pressure-sensitive adhesive layer and a release film layer are obtained. 350g of PET resin (CAS No.: 25038-59-9), 18g of carbon nanotube composite, 80g of epoxy resin, 9g of composite nanoparticles, and 30g of curing agent are mixed and stirred evenly. After intensive mixing, rough mixing, and refining, the mixture is extruded after cooling. After four-roll calendering, embossing, and warm mixing, it is cooled and shaped, then trimmed and wound. After unwinding and corona treatment, a barrier layer is obtained. Polyester film is stacked on the surface of the barrier layer to form a protective layer. The barrier layer and the pressure-sensitive adhesive layer are then bonded together, so that the protective layer, barrier layer, pressure-sensitive adhesive layer, and release film layer are sequentially stacked at the rubber pressure roller and cooling roller to perform multi-layer composite of the adhesive release paper. After winding, corona treatment is performed, and the mixture is dried at 80°C to obtain a heat-insulating window film.

[0046] Example 2

[0047] Preparation of modified carbon nanotubes:

[0048] 4.36 g of polyethyleneimine was mixed with 500 g of deionized water to obtain a polyethyleneimine solution. 10.91 g of carboxylated carbon nanotubes were added to the polyethyleneimine solution to obtain a carbon nanotube dispersion. The carbon nanotube dispersion was refluxed in an oil bath at 120 °C for 12 h, vacuum filtered, and then washed repeatedly with deionized water 5 times. Finally, it was freeze-dried in a vacuum freeze dryer at -20 °C for 18 h to obtain modified carbon nanotubes.

[0049] Preparation of carbon nanotube composites:

[0050] 28.99g of polylactic acid, 8.28g of polybutylene terephthalate (PET) adipate, and 2.73g of modified carbon nanotubes were mixed and stirred under vacuum for 2 hours in a water bath at 25°C to obtain a reactant. The reactant was then evaporated in a fume hood to remove the solvent and fed into a twin-screw extruder for melting and extrusion. After injection molding, the reactant was ground to obtain a carbon nanotube composite.

[0051] Preparation of composite nanoparticles:

[0052] 60g of titanium sulfate was mixed with 900g of deionized water, and then 6g of nano-titanium dioxide powder was added. The mixture was stirred at 25℃ while ammonia was added for hydrolysis until the pH of the system reached 7.5, resulting in a precipitate. The precipitate was filtered and washed with ethanol, then added to 500g of deionized water. 20wt% nitric acid was added until the pH of the system reached 2, thus preparing a silica composite sol. After drying at 45℃, the sol was calcined at 500℃ for 2 hours to obtain silica composite titanium dioxide. 90g of anhydrous ethanol, 90g of toluene, and 6g of perfluorooctyltriethoxysilane were mixed, and the pH of the system was adjusted to 9 with ammonia. Then, 18g of the prepared silica composite titanium dioxide was added. After ultrasonic dispersion, the mixture was centrifuged at 8000rpm for 10 minutes, washed, and dried at 65℃ for 8 hours to obtain composite nanoparticles.

[0053] Preparation of heat-insulating window film:

[0054] Acrylic pressure-sensitive adhesive is coated onto the surface of release paper and allowed to cure at 55°C. After drying, a pressure-sensitive adhesive layer and a release film layer are obtained. 450g of PET resin, 22g of carbon nanotube composite, 110g of epoxy resin, 8.8g of composite nanoparticles, and 50g of curing agent are mixed and stirred evenly. After intensive mixing, rough mixing, and refining, the mixture is extruded after cooling. After four-roll calendering, embossing, and warm mixing, it is cooled and shaped, then trimmed and wound. After unwinding and corona treatment, a barrier layer is obtained. Polyester film is stacked on the surface of the barrier layer to form a protective layer. The barrier layer and the pressure-sensitive adhesive layer are then bonded together. The protective layer, barrier layer, pressure-sensitive adhesive layer, and release film layer are sequentially stacked at the rubber pressure roller and cooling roller to perform multi-layer composite of the adhesive release paper. After winding, corona treatment is performed, and the mixture is dried at 80°C to obtain a heat-insulating window film.

[0055] Example 3

[0056] Preparation of modified carbon nanotubes:

[0057] 2.73 g of polyethyleneimine was mixed with 500 g of deionized water to obtain a polyethyleneimine solution. 9.09 g of carboxylated carbon nanotubes were added to the polyethyleneimine solution to obtain a carbon nanotube dispersion. The carbon nanotube dispersion was refluxed in an oil bath at 120 °C for 12 h, vacuum filtered, and then washed repeatedly with deionized water 5 times. Finally, it was freeze-dried in a vacuum freeze dryer at -20 °C for 18 h to obtain modified carbon nanotubes.

[0058] Preparation of carbon nanotube composites:

[0059] 29.17g of polylactic acid, 8.33g of polybutylene terephthalate (PET) and 2.5g of carbon nanotubes were mixed and stirred under vacuum for 2 hours in a water bath at 25°C to obtain a reactant. The reactant was then evaporated in a fume hood to remove the solvent and fed into a twin-screw extruder for melting and extrusion. After injection molding, the mixture was ground to obtain a carbon nanotube composite.

[0060] Preparation of composite nanoparticles:

[0061] 60g of titanium sulfate was mixed with 900g of deionized water, and then 6g of nano-titanium dioxide powder was added. The mixture was stirred at 25℃ while ammonia was added for hydrolysis until the pH of the system reached 7.5, resulting in a precipitate. The precipitate was filtered and washed with ethanol, then added to 500g of deionized water. 20wt% nitric acid was added until the pH of the system reached 2, thus preparing a silica composite sol. After drying at 45℃, the sol was calcined at 500℃ for 2 hours to obtain silica composite titanium dioxide. 90g of anhydrous ethanol, 90g of toluene, and 6g of perfluorooctyltriethoxysilane were mixed, and the pH of the system was adjusted to 9 with ammonia. Then, 18g of the prepared silica composite titanium dioxide was added. After ultrasonic dispersion, the mixture was centrifuged at 8000rpm for 10 minutes, washed, and dried at 65℃ for 8 hours to obtain composite nanoparticles.

[0062] Preparation of heat-insulating window film:

[0063] Acrylic pressure-sensitive adhesive is coated onto the surface of release paper and allowed to cure at 55°C. After drying, a pressure-sensitive adhesive layer and a release film layer are obtained. 400g of PET resin, 20g of carbon nanotube composite, 90g of epoxy resin, 9g of composite nanoparticles, and 40g of curing agent are mixed and stirred evenly. After intensive mixing, rough mixing, and refining, the mixture is extruded after cooling. After four-roll calendering, embossing, and warm mixing, it is cooled and shaped, then trimmed and wound. After unwinding and corona treatment, a barrier layer is obtained. Polyester film is stacked on the surface of the barrier layer to form a protective layer. The barrier layer and the pressure-sensitive adhesive layer are then bonded together, so that the protective layer, barrier layer, pressure-sensitive adhesive layer, and release film layer are sequentially stacked at the rubber pressure roller and cooling roller to perform multi-layer composite of the adhesive release paper. After winding, corona treatment is performed, and the mixture is dried at 80°C to obtain a heat-insulating window film.

[0064] Example 4

[0065] Example 4 is based on Example 3. In Example 4, when preparing modified carbon nanotubes, 0.91g of polyethyleneimine and 9.09g of carboxylated carbon nanotubes were used.

[0066] Example 5

[0067] Example 5 is based on Example 3. In Example 5, when preparing modified carbon nanotubes, 4.55g of polyethyleneimine and 9.09g of carboxylated carbon nanotubes were used.

[0068] Example 6

[0069] Example 6 is based on Example 3. In Example 6, when preparing the carbon nanotube composite, the polylactic acid used was 29.79g, the polybutylene terephthalate was 8.51g, and the modified carbon nanotubes were 2.26g.

[0070] Example 7

[0071] Example 7 is based on Example 3. In Example 7, when preparing the carbon nanotube composite, 28.57g of polylactic acid, 8.16g of polybutylene terephthalate-adipate, and 3.27g of modified carbon nanotubes were used.

[0072] Example 8

[0073] Example 8 is based on Example 3. In Example 8, when preparing the carbon nanotube composite, the modified carbon nanotubes are replaced with unmodified ordinary carbon nanotubes.

[0074] Example 9

[0075] Example 9 is based on Example 3. The amount of composite nanoparticles added in Example 9 is 6g, and the remainder is made up with PET resin.

[0076] Example 10

[0077] Example 10 is based on Example 3, and the amount of composite nanoparticles added in Example 10 is 12g.

[0078] Example 11

[0079] Example 11 is based on Example 3, except that the composite nanoparticles are replaced with silicon dioxide composite titanium dioxide that has not been treated with perfluorooctyltriethoxysilane.

[0080] Example 12

[0081] Example 12 is based on Example 3. In Example 12, the composite nanoparticles are prepared by mixing nano-silica and nano-titanium dioxide in a mass ratio of 1:1.

[0082] Example 13

[0083] Example 13 is based on Example 3, and the epoxy resin used in Example 13 is 60g.

[0084] Example 14

[0085] Example 14 is based on Example 3, and the epoxy resin used in Example 14 is 120g.

[0086] Comparative Example 1

[0087] Comparative Example 1 is based on Example 3, except that the carbon nanotube composite is replaced with ordinary carbon nanotubes.

[0088] Comparative Example 2

[0089] Comparative Example 2 is based on Example 3, except that the composite nanoparticles are replaced with an equal amount of PET resin.

[0090] Performance testing

[0091] The following performance tests were performed on the samples of Examples 1-14 and Comparative Examples 1-2:

[0092] (1) Thermal insulation performance test

[0093] Using "QC_T 1170-2022 Functional Films for Automotive Glass" as the testing standard, the heat insulation performance of the samples was tested. Each sample was tested 3 times, and the average value was taken. The test results were recorded in Table 1.

[0094] (2) Puncture resistance test

[0095] Using "QC_1171-2022 Automotive Paint Protection Film" as the testing standard, the puncture resistance of the samples was tested. Each sample was tested three times, and the average value was taken. The test results were recorded in Table 1.

[0096] (3) Hydrothermal aging performance test

[0097] After aging the samples at 60℃ and 80% humidity for 72 hours, the infrared blocking performance was tested again. Each sample was tested 3 times, and the test results were recorded in Table 1.

[0098] Table 1. Performance test results of samples from Examples 1-14 and Comparative Examples 1-2

[0099]

[0100]

[0101] As shown in Table 1, the infrared blocking rates of Examples 1-3 are all 92% or higher, indicating that the heat-insulating window film prepared in this application has good heat insulation performance; the puncture resistance of Examples 1-3 is all 202N or higher, indicating that the heat-insulating window film prepared in this application has good strength; and the infrared blocking rates of Examples 1-3 after hydrothermal aging are all 87% or higher, indicating that the heat-insulating window film prepared in this application has good hydrothermal resistance.

[0102] In Examples 4 and 5, the mass ratio of polyethyleneimine to carbon nanotubes during the preparation of modified carbon nanotubes was not within the range specified in this application. When the content of polyethyleneimine was too low, it was difficult to further modify the surface of the carbon nanotubes, and the dispersion of carbon nanotubes in the system was difficult to be further improved, resulting in agglomeration in the system and affecting the overall stability of the system. When the content of polyethyleneimine was too high, the polyethyleneimine coating on the surface of the carbon nanotubes was too thick, and the molecular interaction between the polyethyleneimine of adjacent carbon nanotubes also caused the carbon nanotubes to agglomerate, affecting the overall stability of the system. Therefore, the performance of Examples 4 and 5 was reduced.

[0103] In Examples 6 and 7, the mass ratios of polylactic acid, polybutylene terephthalate (PET), and modified carbon nanotubes during the preparation of the carbon nanotube composites were not within the range specified in this application. When the content of modified carbon nanotubes was too low, it was difficult to further improve the overall mechanical properties of the system. Furthermore, the decrease in the content of carbon nanotubes made it difficult to further improve the overall thermal insulation performance of the system, and it was also difficult to synergistically enhance the overall performance of the system with the composite nanoparticles. When the content of modified carbon nanotubes was too high, the excess modified carbon nanotubes would agglomerate in the system, making it difficult to disperse evenly and affecting the overall comprehensive performance of the system. Therefore, the performance of Examples 6 and 7 was reduced.

[0104] In Example 8, the modified carbon nanotubes were replaced with ordinary unmodified carbon nanotubes. The unmodified carbon nanotubes agglomerated in the system and were difficult to disperse evenly in the system. Furthermore, without polyethyleneimine modification, they were difficult to further combine with epoxy resin, thus resulting in a decrease in overall performance.

[0105] In Examples 9 and 10, the mass ratio between the composite nanoparticles and the carbon nanotube composites was not within the range specified in this application. When the content of composite nanoparticles was too low, the nano-components in the system decreased, making it difficult to synergistically reinforce the resin system with the modified carbon nanotubes, thus affecting the strength of the system. At the same time, it was difficult to further improve the thermal insulation effect of the system, and the hydrophobic properties also decreased. When the content of composite nanoparticles was too high, too many nanomaterials agglomerated in the system, affecting the overall stability of the system. Therefore, the performance of Examples 9 and 10 decreased.

[0106] In Example 11, perfluorooctyltriethoxysilane was not used to treat the silica-composite titanium dioxide. The untreated system could not further improve the overall hydrophobicity, so the water resistance of Example 11 decreased.

[0107] In Example 12, composite nanoparticles were obtained by physically mixing nano-silica and nano-titanium dioxide. Composite nanoparticles obtained by physical mixing alone are difficult to further combine, resulting in decreased stability and agglomeration in the system, which affects the overall stability of the system. Therefore, the performance of Example 12 is reduced.

[0108] In Examples 13 and 14, the mass ratio between epoxy resin and carbon nanotube composite is not within the range specified in this application. When the content of epoxy resin is too high or too low, it is difficult to form a stable bonding effect with the carbon nanotube composite, thereby affecting the overall performance of the system. Therefore, the comprehensive performance of Examples 13 and 14 has decreased.

[0109] In Comparative Example 1, the carbon nanotube composite was replaced with ordinary carbon nanotubes. The modified carbon nanotubes agglomerated in the system, which reduced the overall stability of the system. Therefore, the overall performance of Comparative Example 1 decreased.

[0110] In Comparative Example 2, no composite nanoparticles were added, making it difficult to synergistically improve the overall performance of the system with the carbon nanotube composite. At the same time, the water resistance also decreased. Therefore, the overall performance of Comparative Example 2 was reduced.

[0111] This specific embodiment is merely an explanation of this application and is not intended to limit it. Based on the above description, those skilled in the art can make various changes and modifications without departing from the technical concept of this application. The technical scope of this application is not limited to the contents of the specification but must be determined according to the scope of the claims.

Claims

1. A heat-insulating window film, characterized in that: It includes a protective layer, a barrier layer, a pressure-sensitive adhesive layer, and a release film layer. The barrier layer includes PET resin, carbon nanotube composite, epoxy resin, composite nanoparticles, and a curing agent. The carbon nanotube composite includes modified carbon nanotubes, polylactic acid, and polybutylene terephthalate. The modified carbon nanotubes include carboxylated carbon nanotubes and polyethyleneimine; The modified carbon nanotubes were prepared using the following method: Polyethyleneimine was mixed with water to obtain a polyethyleneimine solution. Carboxylated carbon nanotubes were added to the polyethyleneimine solution to obtain a carbon nanotube dispersion. The carbon nanotube dispersion was refluxed in an oil bath, vacuum filtered, washed and dried to obtain modified carbon nanotubes. The carbon nanotube composite was prepared using the following method: Polylactic acid, polybutylene terephthalate adipate and modified carbon nanotubes were mixed and stirred under water bath conditions to obtain a reactant. After melting, extrusion and injection molding, a carbon nanotube composite was obtained. The composite nanoparticles include silicon dioxide, titanium dioxide, and fluoroalkylsilane.

2. The heat-insulating window film according to claim 1, characterized in that: The mass ratio of polylactic acid, polybutylene terephthalate-adipate and modified carbon nanotubes is 3.5:1:(0.27-0.33).

3. The heat-insulating window film according to claim 1, characterized in that: The mass ratio of the carbon nanotube composite to the epoxy resin is 1:(4-5).

4. The heat-insulating window film according to claim 1, characterized in that: The mass ratio between the composite nanoparticles and the carbon nanotube composite is (1.5-1.4):

1.

5. A method for preparing a heat-insulating window film according to any one of claims 1-4, characterized in that: Includes the following steps: PET resin, carbon nanotube composite, epoxy resin, and curing agent are mixed and stirred evenly. After intensive mixing, roughing and refining processes, the mixture is cooled and extruded, filtered, and then cooled and shaped after four-roll calendering, embossing and warm refining. The edges are then trimmed and rolled up to obtain a barrier layer. The protective layer, barrier layer, pressure-sensitive adhesive layer and release film layer are sequentially composited to prepare a heat-insulating window film.

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