A heterocyclic aramid phase change heat storage film and a preparation method thereof

Abstract

The application relates to the technical field of phase change material preparation, in particular to a heterocyclic aramid phase change heat storage film and a preparation method thereof. After low-temperature polymerization of heterocyclic aramid fibers is completed, the phase change material is coated in situ, an oil-in-oil emulsion is obtained, water exchange is directly carried out, and after drying, a heterocyclic aramid-based phase change film is obtained. The film is dense, and the coating effect is good. Since the prepared phase change film is an integral film material, the phase change film can be directly applied, the processes such as intermediate drying and resolubilization are avoided, the whole process is simple and efficient, the cycle is short, high-end equipment is not depended on, the production cost is low, the coating density is high, the phase change material can be prevented from leaking during phase change, the phase change film has the properties of flame retardation, temperature resistance, excellent mechanical strength and excellent ultraviolet shielding and aging resistance, and the problems of a complicated preparation process, harsh conditions and high cost of the existing phase change heat storage film are solved.

Description

Technical Field

[0001] This invention relates to the field of phase change material preparation technology, specifically to a heterocyclic aramid phase change thermal storage film and its preparation method. Background Technology

[0002] Currently, the most effective methods for addressing the energy crisis and environmental issues are mainly twofold: first, finding new sustainable alternative energy sources; and second, improving the efficiency of existing energy use through the application of advanced energy-saving technologies. Finding new energy sources and applying them to production and daily life is a very long process. Improving energy efficiency through the application of energy-saving technologies is of great significance for the sustainable development of fossil resources. To meet the ever-increasing energy consumption demands, research on energy storage and energy-saving technologies has become a hot topic in the industry. Thermal energy, due to its abundance and availability, has become one of the most promising energy forms. Phase change materials (PCMs), which can store and release large amounts of heat through phase change at relatively constant temperatures, have been proven to effectively store and utilize thermal energy. PCM films can provide a nearly constant-temperature comfortable microclimate to the surrounding environment through the reversible phase change of PCMs, showing great application potential in temperature regulation, thermal energy storage, electrical / solar energy collection, building interior thermal comfort, and smart thermally conditioned textiles.

[0003] Studies have reported that high aspect ratio and amphiphilic cellulose nanofibers (CNFs) can form dense two-dimensional interfacial networks at interfaces, serving as stabilizers for Pickering emulsions and exhibiting excellent stability and templated structures. Using cellulose nanocrystals and nanocellulose as emulsifiers, phase change microcapsules yielded microcapsules with high latent heat and encapsulation rates. Chinese invention publication CN109925985A discloses a method and application for microcapsule encapsulation of phase change materials. This method uses a cellulose nanocrystal-stabilized Pickering emulsion as a template, and prepares an organic polymer or inorganic oxide shell through Pickering emulsion polymerization, in-situ polymerization, or sol-gel reaction, thereby encapsulating organic phase change materials and obtaining organic phase change material microcapsules encapsulated with organic polymers or inorganic oxides. This enables the storage and conversion of thermal energy. However, this method involves complex polymerization reactions, and the final products are mostly granules or powders, which limits their application. In addition, the flammability, poor temperature resistance, easy moisture absorption and deformation, and weak chemical stability of cellulose itself limit the service life of phase change composite materials in harsh environments.

[0004] With the expansion of phase change material (PCM) applications, the performance requirements for materials are becoming increasingly stringent. Developing high-performance, flame-retardant, and integral PCM materials is of great significance for the application of PCM materials in high-end fields. Aramid nanofibers (ANF) possess excellent properties such as high strength, high modulus, flame retardancy, high temperature resistance, and acid and alkali resistance. They have already been combined with PCM materials for application in the field of PCM thermal storage composite materials. Chinese invention patent CN114656663A discloses a Pickering emulsion method for preparing aramid nanofiber-based PCM thermal storage films and its preparation method. This method involves adding PCM materials to an aramid nanofiber dispersion, heating it at a temperature higher than the melting point of the PCM materials to melt them, and stirring to obtain a Pickering emulsion coating the PCM materials with aramid nanofibers. The obtained Pickering emulsion is then cooled to solidify the PCM core material, resulting in microcapsules with aramid nanofibers as the wall material and PCM materials as the core material. Aramid nanofibers (ANFs) offer advantages such as large coating capacity, simplicity, and high efficiency in coating phase change materials (PCMs). They prevent leakage of PCMs during phase transitions while leveraging the inherent properties of aramid nanofibers to impart flame retardancy, temperature resistance, excellent mechanical strength, and outstanding UV shielding and anti-aging properties to the composite material. However, ANF preparation often employs a chemical deprotonation method, which involves a long preparation cycle and high dependence on upstream poly(p-phenylene diamine) (PPTA) fibers as raw materials. Furthermore, the composite process between ANFs and PCMs typically utilizes vacuum impregnation and freeze-drying gelation strategies, which are highly dependent on equipment conditions. This top-down preparation process and reliance on equipment limits its ability to achieve large-scale production. Summary of the Invention

[0005] To address the problems of complex preparation methods, long cycles, demanding equipment requirements, and high costs in existing thermal storage films, this invention provides a heterocyclic aramid phase change thermal storage film and its preparation method.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention provides a method for preparing a heterocyclic aramid phase change thermal storage thin film, comprising:

[0008] A solution system was prepared using N,N-dimethylacetamide and lithium chloride;

[0009] Adding 2-(4-aminophenyl)-5-aminobenzimidazole, 1,4-phenylenediamine and terephthaloyl chloride to the solution system yields a heterocyclic aramid solution;

[0010] A surfactant and a phase change material were added to a heterocyclic aramid solution, and the mixture was heated and homogenized to emulsify, resulting in an oil-in-oil emulsion.

[0011] An oil-in-oil emulsion is coated, immersed in water, and dried to obtain a heterocyclic aramid phase change thermal storage film.

[0012] Furthermore, the solid content of lithium chloride in the solution system is 3wt% to 3.5wt%.

[0013] Furthermore, the molar ratio of 2-(4-aminophenyl)-5-aminobenzimidazole, 1,4-phenylenediamine and terephthaloyl chloride is (9-4):(1-6):10.

[0014] Furthermore, the sum of the molar amounts of 2-(4-aminophenyl)-5-aminobenzimidazole and 1,4-phenylenediamine is equal to the molar amount of terephthaloyl chloride.

[0015] Further, the surfactant is polyethylene glycol-block-polypropylene glycol-block-polyethylene glycol diacrylate and / or polydimethylsiloxane; the amount of surfactant added is 1% to 10% of the mass of the heterocyclic aramid solution.

[0016] Further, the phase change material is one or more of phase change paraffin, octadecane, hexadecane, and docosane; the mass ratio of the amount of phase change material added to the heterocyclic aramid is 1:(1-9).

[0017] Furthermore, the mass ratio of N,N-dimethylacetamide and lithium chloride to heterocyclic aramid is (350–700):(12–24):7.

[0018] Furthermore, the heating temperature is higher than the phase transition temperature of the phase change material.

[0019] Furthermore, the solid content of heterocyclic aramid in the heterocyclic aramid solution is 1wt% to 2wt%.

[0020] A heterocyclic aramid phase change thermal storage film was prepared using the method described above.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] This invention discloses a method for preparing a heterocyclic aramid phase change thermal storage film. A solution system is prepared using N,N-dimethylacetamide and lithium chloride. 2-(4-aminophenyl)-5-aminobenzimidazole, 1,4-phenylenediamine, and terephthaloyl chloride are added to the solution system to obtain a heterocyclic aramid solution. A surfactant and a phase change material are added to the heterocyclic aramid solution, followed by heating and homogenization emulsification to obtain an oil-in-oil emulsion. The oil-in-oil emulsion is coated, immersed in water, and dried to obtain the heterocyclic aramid phase change thermal storage film. This method involves directly coating the phase change material with heterocyclic aramid fibers after low-temperature polymerization to obtain an oil-in-oil emulsion, followed by direct water exchange and drying to obtain a heterocyclic aramid-based phase change film. The film is dense and has good coating effect. Because the prepared phase change film is a monolithic film material, it can be directly applied. The phase change thermal storage film prepared by this method can prevent leakage of phase change materials during phase change while utilizing the inherent properties of heterocyclic aramid fibers to endow the composite material with flame retardancy, temperature resistance, excellent mechanical strength, and outstanding UV shielding and anti-aging properties. Addressing the leakage problem of phase change materials in practical use, this method utilizes in-situ molding and coating with heterocyclic aramid fibers. After polymerization, non-polar long-chain alkanes can be directly coated. The entire process is simple and efficient, and compared with oil-water emulsions, this heterocyclic aramid-based phase change film has a higher coating capacity. Simultaneously, the heterocyclic aramid solution directly forms the film during the exchange process, avoiding intermediate drying and re-dissolution processes. The method is simple, the conditions are mild, it does not rely on high-end equipment, the production cost is low, and the formed film has high density and is not prone to leakage. Compared with phase change microcapsules, it has better mechanical properties and higher heat capacity, showing broad application prospects in the fields of thermal energy storage and temperature control.

[0023] A heterocyclic aramid phase change thermal storage film was prepared using the method described above. Unlike most current powder or granular phase change microcapsules, the heterocyclic aramid phase change thermal storage film is a directly integral film material, which has better encapsulation properties, preventing phase change material leakage. At the same time, it also has the characteristics of good mechanical properties and high heat capacity, and can be directly applied to energy storage and temperature control. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a method for preparing a heterocyclic aramid phase change thermal storage film according to the present invention.

[0025] Figure 2 This is a schematic diagram of the process flow for preparing a heterocyclic aramid phase change thermal storage film according to the present invention.

[0026] Figure 3 This is a microscopic schematic diagram of an oil-in-oil emulsion of heterocyclic aramid coated with octadecane in Example 8 of the present invention.

[0027] Figure 4Thermogravimetric analysis (TGA) diagrams of octadecane / heterocyclic aramid phase change thermal storage films in Examples 6-10 of the present invention.

[0028] Figure 5 The above are DSC curves of octadecane / heterocyclic aramid phase change thermal storage films in Examples 6-10 of the present invention.

[0029] Figure 6 The enthalpy values ​​corresponding to the DSC curves of the octadecane / heterocyclic aramid phase change thermal storage film in Examples 6-10 of the present invention are shown.

[0030] Figure 7 The stress-strain curves of the octadecane / heterocyclic aramid phase change thermal storage film in Examples 6-10 of the present invention are shown. Detailed Implementation

[0031] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0032] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0033] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0034] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0035] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0036] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0037] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0038] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0039] This invention discloses a method for preparing a heterocyclic aramid phase change thermal storage thin film, referring to... Figure 1 and Figure 2 ,include:

[0040] S1: A solution system was prepared using N,N-dimethylacetamide (DMAC) and lithium chloride, as follows:

[0041] Lithium chloride was dissolved in N,N-dimethylacetamide to obtain a solution system with a solid content of 3 wt% to 3.5 wt% of lithium chloride.

[0042] S2: Add 2-(4-aminophenyl)-5-aminobenzimidazole (APBZ), 1,4-phenylenediamine (PPD), and terephthaloyl chloride (TPC) to the solution system to obtain a heterocyclic aramid solution, specifically:

[0043] 2-(4-aminophenyl)-5-aminobenzimidazole and 1,4-phenylenediamine were added to the dissolution system and stirred to dissolve under 0°–5° water bath conditions. Terephthaloyl chloride was then added, the ice bath was removed, and the reaction was allowed to proceed for at least 1 hour to obtain a heterocyclic aramid solution. The sum of the molar amounts of 2-(4-aminophenyl)-5-aminobenzimidazole and 1,4-phenylenediamine was equal to that of terephthaloyl chloride, and the molar ratio of 2-(4-aminophenyl)-5-aminobenzimidazole, 1,4-phenylenediamine, and terephthaloyl chloride was (9–4):(1–6):10. The solid content of heterocyclic aramid (HA) in the heterocyclic aramid solution was 1 wt%–2 wt%, and the mass ratio of N,N-dimethylacetamide, lithium chloride, and heterocyclic aramid was (350–700):(12–24):7.

[0044] S3: Add a surfactant and a phase change material to a heterocyclic aramid solution, heat, and homogenize to emulsify, obtaining an oil-in-oil emulsion, specifically:

[0045] A surfactant is added to a heterocyclic aramid solution, and the mixture is stirred until homogeneous. Then, a long-chain alkane (i.e., a phase change material) is added. The mixture is heated to 30°C–60°C (ensuring the heating temperature is higher than the phase change temperature of the phase change material) and homogenized to emulsify, resulting in an oil-in-oil emulsion of long-chain alkanes coated with heterocyclic aramid and possessing phase change functionality. The surfactant is one or more of polyethylene glycol-block-polypropylene glycol-block-polyethylene glycol diacrylate (F127), polydimethylsiloxane (PEG-10), and alkyl-linked cellulose. The amount of surfactant added is 1%–10% of the mass of the heterocyclic aramid solution. The phase change material is one or more of phase change paraffin, octadecane, hexadecane, and docosane. The mass ratio of the phase change material to the heterocyclic aramid is 1:(1–9).

[0046] S4: Coating an oil-in-oil emulsion, immersing it in water, and drying it yields a heterocyclic aramid phase change thermal storage film, specifically:

[0047] An oil-in-oil emulsion is coated, immersed in water, and dried after water exchange to obtain a heterocyclic aramid fiber-based phase change thermal storage film.

[0048] Example 1

[0049] Lithium chloride was dissolved in N,N-dimethylacetamide to obtain a solution system with a lithium chloride solid content of 3.3 wt%. APBZ and PPD were added to the solution system, and then mechanically stirred under ice-water bath conditions at 0°C until dissolved. TPC was added, the ice-water bath was removed, and the reaction was carried out for 1 hour to obtain a heterocyclic aramid solution. The molar ratio of APBZ, PPD, and TPC was 9:1:10, and the mass ratio of DMAC, LiCl, and heterocyclic aramid was 700:24:7. The heterocyclic aramid solid content in the obtained heterocyclic aramid solution was 1%. 0wt%; 1% of PEG-10 (by mass of the heterocyclic aramid solution) was added to the heterocyclic aramid solution and stirred until dissolved. Then, phase change paraffin was added according to a mass ratio of 1:1 between heterocyclic aramid and phase change paraffin in the solution. The mixture was heated at 60°C and homogenized to emulsify, resulting in an oil-in-oil emulsion of heterocyclic aramid coated with long-chain alkanes having phase change function. The oil-in-oil emulsion was coated, immersed in water for 1 hour, exchanged with water, and then dried at 60°C for 60 minutes to obtain a heterocyclic aramid fiber-based phase change thermal storage film.

[0050] Example 2

[0051] Lithium chloride was dissolved in N,N-dimethylacetamide to obtain a solution system with a lithium chloride solid content of 3.3 wt%. APBZ and PPD were added to the solution system, and the mixture was mechanically stirred at 0°C to dissolve them. TPC was then added, the ice-water bath was removed, and the reaction was allowed to proceed for 1 hour to obtain a heterocyclic aramid solution. The molar ratio of APBZ, PPD, and TPC was 8:2:10, and the mass ratio of DMAC, LiCl, and heterocyclic aramid was 700:24:7. The heterocyclic aramid solid content in the obtained solution was 1.0 wt%. wt%; 1% of PEG-10 (by mass of the heterocyclic aramid solution) was added to the heterocyclic aramid solution and stirred until dissolved. Then, phase change paraffin was added according to a mass ratio of heterocyclic aramid to phase change paraffin in the heterocyclic aramid solution of 1:4. The mixture was heated at 60°C and homogenized to emulsify, resulting in an oil-in-oil emulsion of heterocyclic aramid coated with long-chain alkanes with phase change function. The oil-in-oil emulsion was coated, immersed in water for 1.2 h, exchanged with water, and dried at 60°C for 60 min to obtain a heterocyclic aramid fiber-based phase change heat storage film.

[0052] Example 3

[0053] Lithium chloride was dissolved in N,N-dimethylacetamide to obtain a solution system with a lithium chloride solid content of 3.3 wt%. APBZ and PPD were added to the solution system, and then mechanically stirred until dissolved under an ice-water bath at 0°C. TPC was then added, the ice-water bath was removed, and the reaction was allowed to proceed for 1 hour to obtain a heterocyclic aramid solution. The molar ratio of APBZ, PPD, and TPC was 7:3:10, and the mass ratio of DMAC, LiCl, and heterocyclic aramid was 700:24:7. The heterocyclic aramid solid content in the obtained solution was 1.0 wt%. wt%; 1% of PEG-10 (by mass of the heterocyclic aramid solution) was added to the heterocyclic aramid solution and stirred until dissolved. Then, phase change paraffin was added according to a mass ratio of 1:9 between heterocyclic aramid and phase change paraffin in the solution. The mixture was heated at 60°C and homogenized to emulsify, resulting in an oil-in-oil emulsion of heterocyclic aramid coated with long-chain alkanes having phase change function. The oil-in-oil emulsion was coated, immersed in water for 1.3 h, exchanged with water, and dried at 60°C for 60 min to obtain a heterocyclic aramid fiber-based phase change heat storage film.

[0054] Example 4

[0055] Lithium chloride was dissolved in N,N-dimethylacetamide to obtain a solution system with a lithium chloride solid content of 3.3 wt%. APBZ and PPD were added to the solution system, and then mechanically stirred under ice-water bath conditions at 0°C until dissolved. TPC was then added, the ice-water bath was removed, and the reaction was allowed to proceed for more than 1 hour to obtain a heterocyclic aramid solution. The molar ratio of APBZ, PPD, and TPC was 7:3:10, and the mass ratio of DMAC, LiCl, and heterocyclic aramid was 630:22:7. The heterocyclic aramid solid content in the obtained heterocyclic aramid solution was 1%. 1 wt%; PEG-10, at a mass of 1% of the heterocyclic aramid solution, was added to the heterocyclic aramid solution and stirred until dissolved. Then, phase change paraffin was added according to a mass ratio of heterocyclic aramid to phase change paraffin in the heterocyclic aramid solution of 1:4. The mixture was heated at 60°C and homogenized to emulsify, resulting in an oil-in-oil emulsion of heterocyclic aramid coated with long-chain alkanes with phase change function. The oil-in-oil emulsion was coated, immersed in water for 1.5 h, exchanged with water, and dried at 60°C for 60 min to obtain a heterocyclic aramid fiber-based phase change heat storage film.

[0056] Example 5

[0057] Lithium chloride was dissolved in N,N-dimethylacetamide to obtain a solution system with a lithium chloride solid content of 3.3 wt%. APBZ and PPD were added to the solution system, and then mechanically stirred until dissolved under an ice-water bath at 0°C. TPC was then added, the ice-water bath was removed, and the reaction was allowed to proceed for at least 1 hour to obtain a heterocyclic aramid solution. The molar ratio of APBZ, PPD, and TPC was 6.6:3.4:10, and the mass ratio of DMAC, LiCl, and heterocyclic aramid was 630:22:7. The solid content of heterocyclic aramid in the obtained heterocyclic aramid solution was... The content is 1.1 wt%. 5% of F127 (by mass of the heterocyclic aramid solution) is added to the heterocyclic aramid solution and stirred until dissolved. Then, n-octadecane is added according to a mass ratio of 1:1 between heterocyclic aramid and n-octadecane in the heterocyclic aramid solution. The mixture is heated at 35°C and homogenized to emulsify, resulting in an oil-in-oil emulsion of long-chain alkanes with phase change function coated with heterocyclic aramid. The oil-in-oil emulsion is coated, immersed in water for 1.7 h, exchanged with water, and dried at 70°C for 45 min to obtain a heterocyclic aramid fiber-based phase change heat storage film.

[0058] Example 6

[0059] Lithium chloride was dissolved in N,N-dimethylacetamide to obtain a solution system with a lithium chloride solid content of 3.3 wt%. APBZ and PPD were added to the solution system, and then mechanically stirred until dissolved under an ice-water bath at 0°C. TPC was then added, the ice-water bath was removed, and the reaction was allowed to proceed for 1 hour to obtain a heterocyclic aramid solution. The molar ratio of APBZ, PPD, and TPC was 6:3.4:10, and the mass ratio of DMAC, LiCl, and heterocyclic aramid was 580:20:7. The heterocyclic aramid solid content in the obtained solution was 1.2 wt%. F127, at 5% of the mass of the heterocyclic aramid solution, was added to the heterocyclic aramid solution and stirred until dissolved. Then, n-octadecane was added according to a 1:1 mass ratio of heterocyclic aramid to n-octadecane in the heterocyclic aramid solution. The mixture was heated at 35°C and homogenized to emulsify, resulting in an oil-in-oil emulsion of long-chain alkanes with phase change function coated with heterocyclic aramid. The oil-in-oil emulsion was coated, immersed in water for 1.5 hours, exchanged with water, and dried at 70°C for 45 minutes to obtain a heterocyclic aramid fiber-based phase change heat storage film, denoted as OD50% / HA film.

[0060] Example 7

[0061] Lithium chloride was dissolved in N,N-dimethylacetamide to obtain a solution system with a lithium chloride solid content of 3.3 wt%. APBZ and PPD were added to the solution system, and then mechanically stirred until dissolved under an ice-water bath at 0°C. TPC was then added, the ice-water bath was removed, and the reaction was allowed to proceed for 1 hour to obtain a heterocyclic aramid solution. The molar ratio of APBZ, PPD, and TPC was 6.6:3.4:10, and the mass ratio of DMAC, LiCl, and heterocyclic aramid was 580:20:7. The heterocyclic aramid solid content in the obtained solution was 1.2 wt%. F127, at 5% of the mass of the heterocyclic aramid solution, was added to the heterocyclic aramid solution and stirred until dissolved. Then, n-octadecane was added according to a mass ratio of heterocyclic aramid to n-octadecane of 1:1.5. The mixture was heated at 35°C and homogenized to emulsify, resulting in an oil-in-oil emulsion of heterocyclic aramid coated with long-chain alkanes with phase change function. The oil-in-oil emulsion was coated, immersed in water for 1.5 h, exchanged with water, and dried at 70°C for 45 min to obtain a heterocyclic aramid fiber-based phase change heat storage film, denoted as OD60% / HA film.

[0062] Example 8

[0063] Lithium chloride was dissolved in N,N-dimethylacetamide to obtain a solution system with a lithium chloride solid content of 3.3 wt%. APBZ and PPD were added to the solution system, and then mechanically stirred until dissolved under an ice-water bath at 0°C. TPC was then added, the ice-water bath was removed, and the reaction was allowed to proceed for 1 hour to obtain a heterocyclic aramid solution. The molar ratio of APBZ, PPD, and TPC was 6.6:3.4:10, and the mass ratio of DMAC, LiCl, and heterocyclic aramid was 580:20:7. The heterocyclic aramid solid content in the obtained solution was 1.2 wt%. F127, at 5% of the mass of the heterocyclic aramid solution, was added to the heterocyclic aramid solution and stirred until dissolved. Then, n-octadecane was added according to a mass ratio of heterocyclic aramid to n-octadecane of 1:2.3. The mixture was heated at 35°C and homogenized to emulsify, resulting in an oil-in-oil emulsion of heterocyclic aramid coated with long-chain alkanes with phase change function. The oil-in-oil emulsion was coated, immersed in water for 1.5 h, exchanged with water, and dried at 70°C for 45 min to obtain a heterocyclic aramid fiber-based phase change heat storage film, denoted as OD70% / HA film.

[0064] Example 9

[0065] Lithium chloride was dissolved in N,N-dimethylacetamide to obtain a solution system with a lithium chloride solid content of 3.3 wt%. APBZ and PPD were added to the solution system, and then mechanically stirred until dissolved under an ice-water bath at 0°C. TPC was then added, the ice-water bath was removed, and the reaction was allowed to proceed for 1 hour to obtain a heterocyclic aramid solution. The molar ratio of APBZ, PPD, and TPC was 6.6:3.4:10, and the mass ratio of DMAC, LiCl, and heterocyclic aramid was 580:20:7. The heterocyclic aramid solid content in the obtained solution was 1.2 wt%. Alkyl-linked branched cellulose, at 7% of the mass of the heterocyclic aramid solution, was added to the heterocyclic aramid solution and stirred until dissolved. Then, octadecane was added according to a mass ratio of heterocyclic aramid to octadecane of 1:4. The mixture was heated at 35°C and homogenized to emulsify, resulting in an oil-in-oil emulsion of heterocyclic aramid coated with long-chain alkanes with phase change function. The oil-in-oil emulsion was coated, immersed in water for 1.5 h, exchanged with water, and dried at 70°C for 45 min to obtain a heterocyclic aramid fiber-based phase change thermal storage film, denoted as OD80% / HA film.

[0066] Example 10

[0067] Lithium chloride was dissolved in N,N-dimethylacetamide to obtain a solution system with a lithium chloride solid content of 3.3 wt%. APBZ and PPD were added to the solution system, and then mechanically stirred under ice-water bath conditions at 0°C until dissolved. TPC was added, the ice-water bath was removed, and the reaction was carried out for 1 hour to obtain a heterocyclic aramid solution. The molar ratio of APBZ, PPD and TPC was 6.6:3.4:10, and the mass ratio of DMAC, LiCl and heterocyclic aramid was 580:20:7. The heterocyclic aramid solid content in the obtained heterocyclic aramid solution was 1.2 wt%. Add 5% (by mass) of F127 to the heterocyclic aramid solution and stir until dissolved. Then, add n-octadecane according to a mass ratio of 1:9 (heterocyclic aramid to n-octadecane) in the heterocyclic aramid solution. Heat at 35°C and homogenize to emulsify, obtaining an oil-in-oil emulsion of heterocyclic aramid coated with long-chain alkanes with phase change function. Coat the oil-in-oil emulsion, immerse it in water for 1.5 hours, exchange it with water, and dry it at 70°C for 45 minutes to obtain a heterocyclic aramid fiber-based phase change heat storage film, denoted as OD90% / HA film.

[0068] Example 11

[0069] Lithium chloride was dissolved in N,N-dimethylacetamide to obtain a solution system with a lithium chloride solid content of 3.3 wt%. APBZ and PPD were added to the solution system, and then mechanically stirred until dissolved under an ice-water bath at 0°C. TPC was then added, the ice-water bath was removed, and the reaction was allowed to proceed for 1 hour to obtain a heterocyclic aramid solution. The molar ratio of APBZ, PPD, and TPC was 5:5:10, and the mass ratio of DMAC, LiCl, and heterocyclic aramid was 466:16.3:7. The heterocyclic aramid solid content in the obtained solution was 1%. 0.5wt%; PEG-10 at 7% of the mass of the heterocyclic aramid solution was added to the heterocyclic aramid solution and stirred until dissolved. Then, hexadecane was added at a mass ratio of 1:1 between heterocyclic aramid and hexadecane in the solution. The mixture was heated at 30°C and homogenized to emulsify, resulting in an oil-in-oil emulsion of heterocyclic aramid coated with long-chain alkanes with phase change function. The oil-in-oil emulsion was coated, immersed in water for 1.8 h, exchanged with water, and dried at 80°C for 30 min to obtain a heterocyclic aramid fiber-based phase change heat storage film.

[0070] Example 12

[0071] Lithium chloride was dissolved in N,N-dimethylacetamide to obtain a solution system with a lithium chloride solid content of 3.3 wt%. APBZ and PPD were added to the solution system, and then mechanically stirred until dissolved under an ice-water bath at 0°C. TPC was then added, the ice-water bath was removed, and the reaction was allowed to proceed for 1 hour to obtain a heterocyclic aramid solution. The molar ratio of APBZ, PPD, and TPC was 5:5:10, and the mass ratio of DMAC, LiCl, and heterocyclic aramid was 466:16.3:7. The heterocyclic aramid solid content in the obtained solution was 1%. 0.5wt%; PEG-10 at 7% of the mass of the heterocyclic aramid solution was added to the heterocyclic aramid solution and stirred until dissolved. Then, hexadecane was added according to the mass ratio of heterocyclic aramid to hexadecane in the heterocyclic aramid solution of 1:4. The mixture was heated at 30°C and homogenized to emulsify, resulting in an oil-in-oil emulsion of heterocyclic aramid coated with long-chain alkanes with phase change function. The oil-in-oil emulsion was coated, immersed in water for 1.8h, exchanged with water, and dried at 80°C for 30min to obtain a heterocyclic aramid fiber-based phase change heat storage film.

[0072] Example 13

[0073] Lithium chloride was dissolved in N,N-dimethylacetamide to obtain a solution system with a lithium chloride solid content of 3.3 wt%. APBZ and PPD were added to the solution system, and then mechanically stirred until dissolved under an ice-water bath at 4°C. TPC was then added, the ice-water bath was removed, and the reaction was allowed to proceed for 1 hour to obtain a heterocyclic aramid solution. The molar ratio of APBZ, PPD, and TPC was 5:5:10, and the mass ratio of DMAC, LiCl, and heterocyclic aramid was 466:16.3:7. The heterocyclic aramid solid content in the obtained solution was 1%. 0.5wt%; PEG-10 at 7% of the mass of the heterocyclic aramid solution was added to the heterocyclic aramid solution and stirred until dissolved. Then, hexadecane was added according to the mass ratio of heterocyclic aramid to hexadecane in the heterocyclic aramid solution of 1:9. The mixture was heated at 30°C and homogenized to emulsify, resulting in an oil-in-oil emulsion of heterocyclic aramid coated with long-chain alkanes with phase change function. The oil-in-oil emulsion was coated, immersed in water for 1.8h, exchanged with water, and dried at 80°C for 30min to obtain a heterocyclic aramid fiber-based phase change heat storage film.

[0074] Example 14

[0075] Lithium chloride was dissolved in N,N-dimethylacetamide to obtain a solution system with a lithium chloride solid content of 3.3 wt%. APBZ and PPD were added to the solution system, and then mechanically stirred under an ice-water bath at 5 °C until dissolved. TPC was then added, the ice-water bath was removed, and the reaction was allowed to proceed for 1 h to obtain a heterocyclic aramid solution. The molar ratio of APBZ, PPD, and TPC was 4:6:10, and the mass ratio of DMAC, LiCl, and heterocyclic aramid was 400:14:7. The heterocyclic aramid solid content in the obtained heterocyclic aramid solution was 1%. 75wt%; 10% of F127 (by mass of the heterocyclic aramid solution) was added to the heterocyclic aramid solution and stirred until dissolved. Then, docosane was added according to a 1:1 mass ratio of heterocyclic aramid to docosane in the heterocyclic aramid solution. The mixture was heated at 60°C and homogenized to emulsify, resulting in an oil-in-oil emulsion of long-chain alkanes with phase change function coated with heterocyclic aramid. The oil-in-oil emulsion was coated, immersed in water for 2 hours, exchanged with water, and dried at 80°C for 30 minutes to obtain a heterocyclic aramid fiber-based phase change thermal storage film.

[0076] Example 15

[0077] Lithium chloride was dissolved in N,N-dimethylacetamide to obtain a solution system with a lithium chloride solid content of 3.3 wt%. APBZ and PPD were added to the solution system, and then mechanically stirred under ice-water bath conditions at 0°C until dissolved. TPC was added, the ice-water bath was removed, and the reaction was carried out for 1 hour to obtain a heterocyclic aramid solution. The molar ratio of APBZ, PPD, and TPC was 4:6:10, and the mass ratio of DMAC, LiCl, and heterocyclic aramid was 350:12:7. The heterocyclic aramid solid content in the obtained heterocyclic aramid solution was 2%. 0wt%; 10% of F127 (by mass of the heterocyclic aramid solution) was added to the heterocyclic aramid solution and stirred until dissolved. Then, docosane was added according to a mass ratio of 1:4 between heterocyclic aramid and docosane in the solution. The mixture was heated at 60°C and homogenized to emulsify, resulting in an oil-in-oil emulsion of long-chain alkanes with phase change function coated with heterocyclic aramid. The oil-in-oil emulsion was coated, immersed in water for 2 hours, exchanged with water, and dried at 80°C for 30 minutes to obtain a heterocyclic aramid fiber-based phase change thermal storage film.

[0078] Example 16

[0079] Lithium chloride was dissolved in N,N-dimethylacetamide to obtain a solution system with a lithium chloride solid content of 3.3 wt%. APBZ and PPD were added to the solution system, and then mechanically stirred under ice-water bath conditions at 0°C until dissolved. TPC was added, the ice-water bath was removed, and the reaction was carried out for 1 hour to obtain a heterocyclic aramid solution. The molar ratio of APBZ, PPD, and TPC was 4:6:10, and the mass ratio of DMAC, LiCl, and heterocyclic aramid was 350:12:7. The heterocyclic aramid solid content in the obtained heterocyclic aramid solution was 2%. 0wt%; 10% of F127 (by mass of the heterocyclic aramid solution) was added to the heterocyclic aramid solution and stirred until dissolved. Then, docosane was added according to a mass ratio of 1:9 between heterocyclic aramid and docosane in the solution. The mixture was heated at 60°C and homogenized to emulsify, resulting in an oil-in-oil emulsion of heterocyclic aramid coated with long-chain alkanes with phase change function. The oil-in-oil emulsion was coated, immersed in water for 2 hours, exchanged with water, and dried at 80°C for 30 minutes to obtain a heterocyclic aramid fiber-based phase change thermal storage film.

[0080] Example 17

[0081] Lithium chloride was dissolved in N,N-dimethylacetamide to obtain a solution system with a lithium chloride solid content of 3.5 wt%. APBZ and PPD were added to the solution system, and then mechanically stirred until dissolved under an ice-water bath at 0°C. TPC was then added, the ice-water bath was removed, and the reaction was allowed to proceed for 1 hour to obtain a heterocyclic aramid solution. The molar ratio of APBZ, PPD, and TPC was 4:6:10, and the mass ratio of DMAC, LiCl, and heterocyclic aramid was 350:12:7. The heterocyclic aramid solid content in the obtained solution was 2.0 wt%. [The remaining text appears to be a fragment and requires further context for accurate translation.] 5% F127 and 5% PEG-10 by mass of the heterocyclic aramid solution were added to the heterocyclic aramid solution and stirred until dissolved. Then, mixed phase change materials were added according to the mass ratio of heterocyclic aramid to docosane, n-octadecane and phase change paraffin in the heterocyclic aramid solution of 1:3:3:3. The mixture was heated at 60°C and homogenized to emulsify, resulting in an oil-in-oil emulsion of heterocyclic aramid coated with long-chain alkanes with phase change function. The oil-in-oil emulsion was coated, immersed in water for 2 hours, exchanged with water, and dried at 80°C for 30 minutes to obtain a heterocyclic aramid fiber-based phase change heat storage film.

[0082] Example 18

[0083] Lithium chloride was dissolved in N,N-dimethylacetamide to obtain a solution system with a lithium chloride solid content of 3 wt%. APBZ and PPD were added to the solution system, and then mechanically stirred until dissolved under an ice-water bath at 0°C. TPC was then added, the ice-water bath was removed, and the reaction was allowed to proceed for 1 hour to obtain a heterocyclic aramid solution. The molar ratio of APBZ, PPD, and TPC was 4:6:10, and the mass ratio of DMAC, LiCl, and heterocyclic aramid was 350:12:7. The heterocyclic aramid solid content in the obtained solution was 2.0 wt%. The mass of the heterocyclic aramid solution was... 2% F127 and 5% PEG-10 were added to a heterocyclic aramid solution and stirred until dissolved. Then, a mixed phase change material was added according to the mass ratio of heterocyclic aramid to hexadecane, n-octadecane, docosane and phase change paraffin in the heterocyclic aramid solution of 1:1:1:1:1. The mixture was heated at 60°C and homogenized to emulsify, resulting in an oil-in-oil emulsion of heterocyclic aramid coated with long-chain alkanes with phase change function. The oil-in-oil emulsion was coated, immersed in water for 2 hours, exchanged with water, and dried at 80°C for 30 minutes to obtain a heterocyclic aramid fiber-based phase change heat storage film.

[0084] Taking Examples 6-10 as examples, the performance of the phase change thin films prepared in this invention was tested. See [link to relevant documentation]. Figure 3 Microscopic testing was performed on the oil-in-oil emulsion during the preparation of the phase change film in Example 8. It was found that when the temperature was above the phase change temperature of the phase change material (OD), oil droplets of varying sizes and diameters (less than 35 μm) existed in the emulsion. When the emulsion temperature naturally cooled to below the OD phase change temperature, the oil droplets crystallized instantaneously. This indicates the good dispersibility and stability of OD in the oil-in-oil emulsion and the extensive coating of OD by HA, forming a heterocyclic aramid fiber-coated octadecane structure. See also Figure 4 Thermogravimetric analysis of the phase change films prepared in Examples 6-10 showed a coating rate of 62%, indicating that heterocyclic aramid fibers possess excellent film-forming properties and the film-forming method is simple. The films have a dense structure, which is beneficial for extensive coating of phase change materials and preventing leakage during the phase change process. See also Figure 5 and Figure 6 DSC tests were performed on the phase change films prepared in Examples 6-10. The results showed that the phase change film with a coating rate of 62% could store 167.9 J / g of energy, indicating that the film has extremely high coating amount and heat capacity, which is of great significance for subsequent thermal management applications. See also Figure 7 Mechanical property tests were conducted, and the results showed that the fracture stress of the film was about 14.70 MPa, and the maximum ultimate tensile strain was about 44.62%. The fracture strain was significantly improved compared with that of the heterocyclic aramid fiber film, indicating that the addition of phase change material can improve the brittleness of the heterocyclic aramid fiber film.

[0085] This invention also provides a heterocyclic aramid phase change thermal storage film, prepared using the method described above. Unlike most current powder or granular phase change microcapsules, the heterocyclic aramid phase change thermal storage film is a directly integral film material, exhibiting better encapsulation properties. While preventing phase change material leakage, it also possesses excellent mechanical properties and high heat capacity, enabling direct application in energy storage and temperature control.

[0086] In summary, this invention provides a heterocyclic aramid phase change thermal storage film and its preparation method. This method involves directly coating a phase change material with heterocyclic aramid fibers after low-temperature polymerization to obtain an oil-in-oil emulsion, followed by direct water exchange and drying to obtain a heterocyclic aramid-based phase change film. The film is dense and exhibits excellent coating performance. Because the phase change film prepared by this method is a monolithic film material, it can be directly applied. The entire process is simple and efficient, with high coating density. Compared to oil-water emulsions, this heterocyclic aramid-based phase change film has a higher coating capacity, preventing leakage of the phase change material during phase change. Simultaneously, the inherent properties of the heterocyclic aramid fibers endow the composite material with flame retardancy, temperature resistance, excellent mechanical strength, and outstanding UV shielding and anti-aging properties. This method improves upon the drawbacks of combining heterocyclic aramid fibers with phase change materials, while simultaneously achieving stable, large-scale coating and rapid encapsulation of phase change materials. This method improves the service capability and lifespan of phase change materials in harsh environments such as high temperature and high humidity, enabling them to meet the requirements of high-end applications. The resulting high heat capacity monolithic thin film material has good application prospects in energy storage and temperature control, and the preparation method is simple, the reaction conditions are mild, the reaction cycle is short, and it is suitable for industrialization.

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A method for preparing a heterocyclic aramid phase change thermal storage thin film, characterized in that, include: A solution system was prepared using N,N-dimethylacetamide and lithium chloride; 2-(4-aminophenyl)-5-aminobenzimidazole, 1,4-phenylenediamine and terephthaloyl chloride were added to the solution to obtain a heterocyclic aramid solution; wherein the molar ratio of 2-(4-aminophenyl)-5-aminobenzimidazole, 1,4-phenylenediamine and terephthaloyl chloride was (9-4):(1-6):10; A surfactant and a phase change material are added to a heterocyclic aramid solution, and the mixture is heated and homogenized to emulsify, yielding an oil-in-oil emulsion. The surfactant is polyethylene glycol-block-polypropylene glycol-block-polyethylene glycol diacrylate and / or polydimethylsiloxane. The phase change material is one or more of phase change paraffin, octadecane, hexadecane, and docosane. The mass ratio of the phase change material to the heterocyclic aramid is 1:(1-9). An oil-in-oil emulsion is coated, immersed in water, and dried to obtain a heterocyclic aramid phase change thermal storage film.

2. The method for preparing heterocyclic aramid phase change thermal storage thin film according to claim 1, characterized in that, In the solution system, the solid content of lithium chloride is 3wt% to 3.5wt%.

3. The method for preparing heterocyclic aramid phase change thermal storage thin film according to claim 1, characterized in that, The sum of the molar amounts of 2-(4-aminophenyl)-5-aminobenzimidazole and 1,4-phenylenediamine is equal to the molar amount of terephthaloyl chloride.

4. The method for preparing heterocyclic aramid phase change thermal storage thin film according to claim 1, characterized in that, The amount of surfactant added is 1% to 10% of the mass of the heterocyclic aramid solution.

5. The method for preparing heterocyclic aramid phase change thermal storage thin film according to claim 1, characterized in that, The mass ratio of N,N-dimethylacetamide and lithium chloride to heterocyclic aramid is (350-700):(12-24):

7.

6. The method for preparing heterocyclic aramid phase change thermal storage thin film according to claim 1, characterized in that, The heating temperature is higher than the phase transition temperature of the phase change material.

7. The method for preparing heterocyclic aramid phase change thermal storage thin films according to any one of claims 1-6, characterized in that, The solid content of heterocyclic aramid in the heterocyclic aramid solution is 1wt% to 2wt%.

8. A heterocyclic aramid phase change thermal storage film, characterized in that, Prepared using the method described in any one of claims 1-7.

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