Preparation method and application of polypyrrole-urea resin cross-linked photo-thermal energy storage phase change microcapsule

Abstract

The invention discloses a preparation method and application of a polypyrrole-urea resin cross-linked photo-thermal energy storage phase change microcapsule, and aims to solve the problems that an existing photo-thermal conversion material and a phase change energy storage material are compounded, interface bonding between the photo-thermal conversion material and the phase change material is not firm and the like. The preparation method comprises the following steps: 1, pretreating a pyrrole monomer and a phase change material; 2, mixing a phase change material and a pyrrole monomer to prepare an oil phase, and adding the oil phase into the water phase to obtain a water-in-oil emulsion; 3, mixing a ferric chloride solution with the urea formaldehyde prepolymer solution, adjusting the pH value of the system to 3-4, and dropwise adding the mixed solution into the water-in-oil emulsion to obtain a reaction solution; 4, heating and carrying out a cross-linking reaction; 5, blocking and stabilizing; and 6, washing and drying. According to the preparation method disclosed by the invention, simultaneous coating of polypyrrole and urea-formaldehyde resin is realized through a one-step method cooperating with in-situ polymerization, the two polymers form an interpenetrating network structure on an oil-water interface, and the special structure remarkably improves the mechanical strength and thermal stability of the microcapsule.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of a poly-pyrrole-urea-formaldehyde resin cross-linked phase change microcapsule material. BACKGROUND

[0002] In the field of energy utilization and storage, phase change energy storage materials have attracted much attention due to their large latent heat and temperature stability. Currently, phase change energy storage materials mainly have single function, i.e. only have the function of heat storage. Such materials have serious limitations in practical application: first, traditional phase change materials can only passively absorb heat from the environment for storage, and cannot actively convert other forms of energy, especially renewable energy such as solar energy, into heat and store it; second, the thermal conductivity of phase change materials is low, and the heat absorption and release process is slow, which seriously affects the efficiency of energy conversion and storage; third, most phase change materials have the problem of significant volume change during phase change, which not only affects the energy storage effect, but also easily leads to the destruction of the coating structure. In addition, existing phase change materials often need additional heat conduction structures or devices to improve the heat transfer efficiency in practical application, which greatly increases the complexity and cost of the system.

[0003] To solve the above problems, researchers have proposed various improvement schemes, including adding heat-conducting fillers and constructing composite phase change materials. However, these schemes often bring new technical challenges while solving a certain problem. For example, adding heat-conducting fillers can improve the thermal conductivity of the material, but at the same time, it will reduce the phase change latent heat and energy storage density of the material; constructing composite phase change materials can introduce new functions, but due to the poor interface compatibility between materials, it is easy to cause performance instability and short service life, etc. In particular, in the preparation of microencapsulated phase change materials, existing technologies generally have the problems of incomplete coating, insufficient mechanical strength, poor cycle stability, etc. These defects mainly manifest in: the coating layer is easy to crack, causing core material leakage; microcapsules are easy to break during repeated phase change cycles; performance fluctuates greatly between batches, making it difficult to achieve large-scale production. More importantly, existing phase change microcapsules still cannot effectively solve the problem of active energy capture, which seriously limits their application in the field of renewable energy utilization.

[0004] Currently, some researchers try to composite photothermal conversion materials with phase change energy storage materials in order to realize the synergistic effect of photothermal conversion and phase change energy storage. However, such composite materials still face many challenges in practical application: first, the interface between the photothermal conversion material and the phase change material is not firm, and phase separation easily occurs, resulting in a decrease in photothermal conversion efficiency; second, the preparation process of the composite material is usually complex, involving multiple steps and strict process parameter control, which not only increases the production cost, but also brings difficulties to product quality control; third, the structure design of the existing composite material is often not reasonable, which is difficult to ensure good photothermal conversion performance and phase change energy storage effect at the same time. In addition, such composite materials are prone to performance degradation during long-term use, especially the decrease in photothermal conversion efficiency and the loss of phase change energy storage capacity, which seriously affects the practical application value of the material.

[0005] In terms of production process, the existing technology also has significant deficiencies. The traditional microencapsulation method usually adopts a step-by-step synthesis method, i.e., first preparing a phase change core material emulsion, and then synthesizing a coating layer. This method not only has a long process flow and complex operation, but also makes it difficult to control the particle size distribution and morphology of the product. At the same time, the step-by-step synthesis method also makes it difficult to ensure the effective composite between the functional layers, often resulting in problems such as weak interface bonding and unstable interlayer structure. Especially when introducing photothermal conversion function, due to the difference in material properties, it is difficult to ensure good photothermal conversion effect while ensuring phase change energy storage performance. In addition, the existing process has high cost, high energy consumption, and poor batch stability, which restricts the large-scale industrial application of related products. SUMMARY

[0006] The present application is to solve the problems of the existing composite of photothermal conversion materials and phase change energy storage materials, weak interface bonding between photothermal conversion materials and phase change materials, and complex step-by-step synthesis process, and to provide a microcapsule with both photothermal conversion and phase change energy storage functions by in-situ polymerization of a polypyrrole photothermal conversion layer and a urea-formaldehyde resin protective layer to coat the phase change material, so as to realize efficient capture, conversion and storage of solar energy.

[0007] The preparation method of the polypyrrole-urea-formaldehyde resin cross-linked photothermal energy storage phase change microcapsule according to the present application is realized according to the following steps:

[0008] I. Pretreatment and purification of raw materials:

[0009] The pyrrole monomer is placed in a reaction bottle and subjected to reduced pressure distillation at a temperature of 70-80℃. The colorless transparent fraction collected at 70-72℃ is the purified pyrrole monomer;

[0010] The phase change material is mixed with activated carbon and pretreated by stirring at 55-65℃. After removing the activated carbon by suction filtration, the filtrate is subjected to reduced pressure distillation to obtain the pretreated phase change material;

[0011] II. Construction of emulsion system:

[0012] The surfactant is dissolved in deionized water, and sodium dodecyl sulfate is added as an emulsifier to obtain an aqueous phase; the pretreated phase change material and the purified pyrrole monomer are mixed to prepare an oil phase, and the oil phase is (slowly) added to the aqueous phase at low temperature and subjected to shear emulsification treatment to obtain a water-in-oil emulsion;

[0013] III. Initiation of synergistic polymerization:

[0014] The iron chloride solution with a concentration of 0.6-1.5 mol / L is mixed with the urea-formaldehyde prepolymer solution, and the pH of the system is adjusted to 3-4 with citric acid to obtain a mixed solution, which is then added dropwise to the water-in-oil emulsion, and the stirring reaction is carried out at 10-15 DEG C to obtain a reaction liquid;

[0015] IV. Synergistic growth process:

[0016] The reaction liquid is warmed to 45-55 DEG C for further crosslinking reaction to obtain a polymerization product reaction liquid;

[0017] V. End-capping and stabilization:

[0018] The mixed solution of hydroquinone and triethanolamine is added to the polymerization product reaction liquid for end-capping treatment to obtain a stabilized reaction liquid;

[0019] VI. Post-reaction treatment:

[0020] The stabilized reaction liquid is subjected to centrifugal separation to collect the solid phase, which is washed and dried to obtain a polypyrrole-urea-formaldehyde resin crosslinked photo-thermal energy storage phase change microcapsule;

[0021] The phase change material in step I is an alkane, a fatty acid or a fatty acid ester with a carbon number of 12-20.

[0022] The application of the polypyrrole-urea-formaldehyde resin crosslinked photo-thermal energy storage phase change microcapsule is to apply the polypyrrole-urea-formaldehyde resin crosslinked photo-thermal energy storage phase change microcapsule as a wall coating, a vehicle coating, a textile coating, a heat conducting working medium or a composite film in a membrane assembly.

[0023] The preparation method and application of the polypyrrole-urea-formaldehyde resin crosslinked photo-thermal energy storage phase change microcapsule have the following beneficial effects:

[0024] 1. The present application realizes the simultaneous coating of polypyrrole and urea-formaldehyde resin by one-step method in situ polymerization, overcoming the problem of weak interface combination in traditional step-by-step synthesis. The two polymers form an interpenetrating network structure at the oil-water interface, which significantly improves the mechanical strength and thermal stability of the microcapsule, so that the product can maintain good morphology and performance after more than 1000 thermal cycles.

[0025] 2. The use of As a bifunctional catalyst, it not only initiates the oxidative polymerization of pyrrole, but also promotes the crosslinking reaction of urea-formaldehyde resin, simplifying the reaction system. This synergistic catalysis improves the reaction efficiency, so that the growth rate of the two polymers matches, forming a uniform and dense composite shell layer, and the encapsulation rate of the product can reach more than 90%.

[0026] 3. The preparation method of the present application is simple, the reaction is carried out under mild conditions (temperature ≤ 60℃, normal pressure), and the raw materials used are conventional chemical products, which is low in cost. The entire reaction process does not require the use of organic solvents, and the reaction wastewater can be recycled, which meets the principles of green chemistry and has good prospects for industrial application.

[0027] 4. The prepared microcapsule has excellent light-heat conversion performance and phase change energy storage characteristics, with a light-heat conversion efficiency of more than 45% and a phase change latent heat of 180 J / g. The product can quickly heat up under light conditions (heating rate > 1.5℃ / min), and continuously release heat for more than 2 hours without light, realizing intelligent regulation of active and passive energy storage.

[0028] 5. The microcapsule has a narrow particle size distribution (CV value < 15%), regular morphology and good dispersibility, which makes it have good processing performance in actual application. The product can be compounded with various matrix materials, showing excellent application effect in the fields of building energy-saving coatings and intelligent temperature control textiles, and can meet the actual needs of different fields. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The electron micrograph of the polypyrrole-urea-formaldehyde resin crosslinked light-heat energy storage phase change microcapsule obtained by the example;

[0030] Figure 2 The phase change thermal test graph of the polypyrrole-urea-formaldehyde resin crosslinked light-heat energy storage phase change microcapsule obtained by the example;

[0031] Figure 3 The temperature change test graph of the polypyrrole-urea-formaldehyde resin crosslinked light-heat energy storage phase change microcapsule obtained by the example under-10℃ environment, under one solar intensity and with light switching. DETAILED DESCRIPTION

[0032] Specific embodiment one: the preparation method of the poly-pyrrole-urea-formaldehyde resin cross-linked photo-thermal energy storage phase change microcapsule in the embodiment is implemented according to the following steps:

[0033] I. Pretreatment and purification of raw materials:

[0034] The pyrrole monomer is placed in a reaction bottle, and vacuum distillation is performed at a temperature of 70-80 DEG C. The colorless transparent fraction collected at 70-72 DEG C is obtained, and the purified pyrrole monomer is obtained.

[0035] The phase change material is mixed with activated carbon, and pretreated at 55-65 DEG C under stirring. After removing the activated carbon by suction filtration, the filtrate is vacuum distilled to obtain the pretreated phase change material.

[0036] II. Construction of emulsion system:

[0037] The surfactant is dissolved in deionized water, and sodium dodecyl sulfate is added as an emulsifier to obtain the water phase. The pretreated phase change material and the purified pyrrole monomer are mixed to prepare the oil phase, and the oil phase is slowly added to the water phase at low temperature and subjected to shear emulsification treatment to obtain a water-in-oil emulsion.

[0038] III. Initiation of synergistic polymerization:

[0039] The iron chloride solution with a concentration of 0.6-1.5 mol / L is mixed with the urea-formaldehyde prepolymer solution, and the pH of the system is adjusted to 3-4 with citric acid to obtain a mixed solution. Then the mixed solution is added dropwise to the water-in-oil emulsion, and the stirring reaction is carried out at 10-15 DEG C to obtain a reaction liquid.

[0040] IV. Synergistic growth process:

[0041] The reaction liquid is heated to 45-55 DEG C to continue the crosslinking reaction, and a polymerization product reaction liquid is obtained.

[0042] V. End-capping and stabilization:

[0043] A mixed solution of hydroquinone and triethanolamine is added to the polymerization product reaction liquid for end-capping treatment to obtain a stabilized reaction liquid.

[0044] VI. Post-reaction treatment:

[0045] The stabilized reaction liquid is subjected to centrifugal separation to collect the solid phase, and after washing and drying, a poly-pyrrole-urea-formaldehyde resin cross-linked photo-thermal energy storage phase change microcapsule is obtained.

[0046] The phase change material in step one is an alkane, a fatty acid or a fatty acid ester with a carbon number of 12-20.

[0047] The present embodiment combines in-situ polymerization of polypyrrole and coating of urea-formaldehyde resin to tightly combine the polypyrrole layer with electric conductivity and the phase change material, and then forms a protective layer through cross-linking reaction of the urea-formaldehyde resin, and finally obtains a microcapsule material with dual functions of photo-thermal conversion and phase change energy storage. The microcapsule can convert light energy into heat energy and store it in the phase change material under light conditions, and release the heat through the phase change process of the phase change material under no light conditions, thereby achieving the dual effects of active and passive energy storage.

[0048] The present embodiment combines in-situ polymerization of polypyrrole and coating of urea-formaldehyde resin to tightly combine the polypyrrole layer with electric conductivity and the phase change material, and then forms a protective layer through cross-linking reaction of the urea-formaldehyde resin, and finally obtains a microcapsule material with dual functions of photo-thermal conversion and phase change energy storage. The microcapsule can convert light energy into heat energy and store it in the phase change material under light conditions, and release the heat through the phase change process of the phase change material under no light conditions, thereby achieving the dual effects of active and passive energy storage.

[0049] Specific embodiment two: The present embodiment is different from the specific embodiment one in that the purified pyrrole monomer in step one is placed in a brown reagent bottle and stored at 4°C in the dark.

[0050] Specific embodiment three: The present embodiment is different from the specific embodiment one or two in that the melting point of the phase change material in step one is in the range of -10°C to 50°C.

[0051] Specific embodiment four: The present embodiment is different from one of the specific embodiments one to three in that the mass ratio of the phase change material to activated carbon in step one is 10:1.

[0052] Specific embodiment five: The present embodiment is different from one of the specific embodiments one to four in that the surfactant in step two is polyvinylpyrrolidone, Tween-80 or Span-80.

[0053] Specific embodiment six: The present embodiment is different from one of the specific embodiments one to five in that the mass ratio of the pretreated phase change material to the purified pyrrole monomer in step two is (3-5):1.

[0054] Specific embodiment seven: The present embodiment is different from one of the specific embodiments one to six in that the shearing emulsification in step two is carried out at a speed of 1000 rpm for 20-40 minutes.

[0055] Specific embodiment eight: The present embodiment is different from one of the specific embodiments one to seven in that the stirring reaction in step three is carried out at 10-15°C for 2-2.5 hours.

[0056] Specific embodiment nine: The present embodiment is different from one of the specific embodiments one to eight in that the reaction solution is warmed to 50°C in step four for 1 hour for further cross-linking reaction.

[0057] Specific implementation ten: the difference between this embodiment and one of the specific implementation one to nine is that the concentration of hydroquinone in the mixed solution of hydroquinone and triethanolamine in step five is 0.2wt%-0.4wt%, and the concentration of triethanolamine is 0.4wt%-0.6wt%.

[0058] Embodiment: the preparation method of the poly-pyrrole-urea-formaldehyde resin cross-linked photo-thermal energy storage phase change microcapsul is implemented according to the following steps:

[0059] I. Pretreatment and raw material purification:

[0060] The pyrrole monomer is placed in a three-necked flask, a vacuum distillation device is connected to the three-necked flask, vacuum distillation is carried out under the protection of nitrogen at a pressure of 25.7mmHg, and the vacuum distillation is carried out at a temperature of 75.5℃. Colorless transparent distillate is collected at 70-72℃, and the purified pyrrole monomer is obtained. The purified pyrrole monomer is transferred to a brown reagent bottle and stored in a 4℃ refrigerator in the dark;

[0061] The phase change material tetradecane and activated carbon are mixed in a mass ratio of 10:1, pretreated at 60℃ for 2 hours, and then the activated carbon is removed by suction filtration. The filtrate is subjected to vacuum distillation at 160℃ and 50mmHg to obtain a pretreated phase change material;

[0062] II. Construction of emulsion system:

[0063] Polyvinyl alcohol is dissolved in deionized water, and sodium dodecyl sulfate is added as an emulsifier to obtain an aqueous phase. The concentration of polyvinyl alcohol in the aqueous phase is 3wt%, and the concentration of the emulsifier is 0.2wt%. The pretreated phase change material and the purified pyrrole monomer are mixed in a mass ratio of 4:1 to prepare an oil phase. The oil phase is slowly added to the aqueous phase at a rate of 2mL / min at 13±0.5℃, and simultaneously sheared and emulsified at a rate of 1000rpm for 30 minutes to obtain a water-in-oil emulsion;

[0064] III. Initiation of synergistic polymerization:

[0065] The concentration of the iron chloride solution is 0.8mol / L, and the urea-formaldehyde prepolymer solution is mixed in a volume ratio of 1:1. Citric acid is used to adjust the pH of the system to 3.0±0.2 to obtain a mixed solution. Then the mixed solution is added to the water-in-oil emulsion at a rate of 2mL / min. During this period, the system temperature is maintained at 15±0.5℃, the stirring rate is 250rpm, and the stirring reaction time is 2 hours to obtain a reaction liquid. At this time, It not only serves as an oxidizing agent for pyrrole polymerization, but also catalyzes the cross-linking of urea-formaldehyde resin. Under acidic conditions, the two polymerization reactions proceed simultaneously;

[0066] The urea-formaldehyde prepolymer is a low-molecular-weight (500-2000) water-soluble resin formed by addition and preliminary condensation of urea, formaldehyde, and melamine under alkaline conditions (pH 8.0-9.0). The prepolymer contains a large number of active functional groups and further crosslinks and solidifies under acidic conditions to form a network structure. When preparing the urea-formaldehyde resin prepolymer, the amount of deionized water is controlled to be 40% to 50% of the total solid content of the reactants. That is, when the total mass of melamine, urea, and 37% formaldehyde solution is 100 parts, 60-80 parts of deionized water are required for the reaction. The molar ratio of urea, melamine, and formaldehyde is 1:0.2:2.5.

[0067] 4. Synergistic Growth Process:

[0068] Polypyrrole and urea-formaldehyde resin grow simultaneously on the surface of the oil droplet. Under the action of Fe³⁺, pyrrole forms free radical cations and begins polymerization. Simultaneously, the urea-formaldehyde prepolymer undergoes a condensation reaction under acidic conditions. The two polymers form an interpenetrating network structure through hydrogen bonding and electrostatic interactions. After 2 hours of reaction, the reaction solution is heated to 50°C and the cross-linking reaction is continued for 1 hour to promote the full cross-linking of the urea-formaldehyde resin, resulting in a polymerization product reaction solution (suspension).

[0069] 5. End-capping and stabilization:

[0070] A mixed solution containing 0.2 wt % of hydroquinone and 0.5 wt % of triethanolamine was added to the polymerization product reaction solution for end-capping treatment for 15 minutes to obtain a stabilized reaction solution;

[0071] 6. Post-reaction treatment:

[0072] The product was separated by gradient centrifugation: first centrifugation at 2000 rpm for 10 minutes to remove agglomerates, then centrifugation at 3500 rpm for 15 minutes to collect the target product, and the product was washed three times with ethanol and deionized water in sequence, centrifuged at 4000 rpm for 10 minutes after each wash, and finally vacuum dried at 35°C for 16 hours to obtain polypyrrole-urea-formaldehyde resin cross-linked photothermal energy storage phase change microcapsules.

[0073] Depend on Figure 2 It can be seen that the phase change latent heat of the phase change microcapsule is as high as 180J / g; Figure 3 It can be seen that in an environment of -10℃, when light is irradiated to the surface of the microcapsule, the temperature quickly rises to 80.2℃ within 100s. After the light source is turned off, the temperature of the microcapsule quickly drops to the ambient temperature. After two cycles, the temperature change is stable.

[0074] Application Example One: The poly-pyrrole-urea-formaldehyde resin cross-linked light-heat energy storage phase change microcapsules prepared in the examples are mixed with an acrylic emulsion at a mass ratio of 1:4, and an appropriate amount of thickening agent (0.3wt% hydroxypropyl methyl cellulose) and dispersing agent (0.2wt% sodium hexametaphosphate) are added to prepare a building exterior wall coating. The coating (thickness 300μm) is sprayed on the surface of a concrete wall (1m x 1m), and after 28 days of field testing, it is shown that under the condition of direct sunlight in summer (light intensity 900W / m²), the surface temperature of the coating is reduced by 12-15°C compared with ordinary coatings; the surface temperature of the interior wall is reduced by 8-10°C; and the air conditioning energy consumption is saved by 30-35%. After 200 times of accelerated aging test, the performance attenuation of the coating is less than 5%.

[0075] Application Example Two: The poly-pyrrole-urea-formaldehyde resin cross-linked light-heat energy storage phase change microcapsules prepared in the examples are mixed with an acrylate adhesive at a mass ratio of 1:3, and an impregnation method is used to treat cotton fabric (microcapsule adhesion amount 15-20g / m²). The functional fabric prepared can raise the fabric temperature by 8-10°C within 2 minutes under sunlight irradiation (600W / m²); and can continuously release heat for 90-120 minutes under no light conditions. After 50 times of washing (in accordance with ISO 6330 standard), the microcapsule shedding rate is less than 10%, and the heat preservation effect is reduced by not more than 15%. The fabric can be used to make outdoor sports clothing, and significantly improves the thermal comfort of the clothing.

[0076] Application Example Three: The poly-pyrrole-urea-formaldehyde resin cross-linked light-heat energy storage phase change microcapsules prepared in the examples are mixed with heat-conducting silicone oil at a mass ratio of 3:7 to prepare a composite heat-conducting working medium, which is used in a flat-plate solar heat collector. Test results show that under the typical working conditions in winter (environmental temperature 5°C, light intensity 600W / m²), the heat collection efficiency of the system is increased by 25-30% compared with traditional working media; the night heat storage time is extended by 2-3 hours; and the system start-up time is shortened by 40%. After 1000 hours of cyclic operation, the microcapsule breakage rate is less than 2%, and the system performance remains stable.

[0077] Application Example Four: The poly-pyrrole-urea-formaldehyde resin cross-linked light-heat energy storage phase change microcapsules prepared in the examples are mixed with a two-component polyurethane varnish at a mass ratio of 1:5, and 0.5wt% of nano-silicon dioxide (surface modified) is added as a scratch-resistant agent. An electrostatic spraying process is used to prepare a functional coating on the surface of a car (dry film thickness 45-50μm). Test results show that under the condition of direct sunlight in summer, the coating can reduce the internal temperature of the car compartment by 10-12°C compared with ordinary coatings; the temperature after parking is reduced by 2-3 hours; the coating hardness reaches 4H, and the wear resistance meets the standard of automotive coatings. After 30,000 kilometers of road testing, the performance of the coating does not significantly attenuate.

[0078] Example 5: The light-heat energy storage phase change microcapsules prepared by the polypyrrole-urea-formaldehyde resin of the embodiment are mixed with polyvinylidene fluoride (PVDF) at a mass ratio of 2:3, and a porous composite membrane (membrane thickness 200 μm, porosity 75%) is prepared by electrospinning. Under simulated sunlight irradiation (light intensity 1 kW / m²), the surface temperature of the membrane can rise above 80°C within 1 minute; the water flux reaches 1.2 kg / m²·h, which is 2.5 times that of ordinary PVDF membranes; the desalination rate of salt water (3.5 wt% NaCl) is greater than 99.9%. After continuous operation of the membrane material for 200 hours, the performance decreases by less than 8%.

Claims

1. A method for preparing polypyrrole-urea-formaldehyde resin cross-linked photothermal energy storage phase change microcapsules, characterized in that The preparation method of the polypyrrole-urea-formaldehyde resin cross-linked photothermal energy storage phase change microcapsules is achieved by the following steps:

1. Pretreatment and purification of raw materials: The pyrrole monomer is placed in a reaction bottle, and is subjected to reduced pressure distillation at a temperature of 70-80° C., and a colorless transparent fraction at 70-72° C. is collected to obtain the purified pyrrole monomer; The phase change material is mixed with activated carbon, stirred at 55-65°C for pretreatment, the activated carbon is removed by suction filtration, and the filtrate is subjected to reduced pressure distillation to obtain the pretreated phase change material; 2. Construction of emulsion system: The surfactant is dissolved in deionized water, and sodium lauryl sulfate is added as an emulsifier to obtain an aqueous phase; the pretreated phase change material and the purified pyrrole monomer are mixed to prepare an oil phase, and the oil phase is added to the aqueous phase at low temperature and subjected to shear emulsification treatment to obtain a water-in-oil emulsion; 3. Initiation of collaborative polymerization: A 0.6-1.5 mol / L ferric chloride solution is mixed with a urea-formaldehyde prepolymer solution, and the pH of the system is adjusted to 3-4 with citric acid to obtain a mixed solution. The mixed solution is then added dropwise to the water-in-oil emulsion, and the mixture is stirred and reacted at 10-15° C. to obtain a reaction solution.

4. Synergistic Growth Process: The reaction solution is heated to 45-55°C to continue the cross-linking reaction to obtain a polymer product reaction solution; 5. End-capping and stabilization: adding a mixed solution of hydroquinone and triethanolamine to the polymerization product reaction solution for end-capping treatment to obtain a stabilized reaction solution; 6. Post-reaction treatment: The stabilized reaction solution is centrifuged to collect the solid phase, and after washing and drying, polypyrrole-urea-formaldehyde resin cross-linked photothermal energy storage phase change microcapsules are obtained; The phase change material in step 1 is an alkane, fatty acid or fatty acid ester having a carbon number of 12 to 20.

2. The method for preparing the polypyrrole-urea-formaldehyde resin cross-linked photothermal energy storage phase change microcapsules according to claim 1, characterized in that The purified pyrrole monomer in step 1 was placed in a brown reagent bottle and stored at 4° C. in the dark.

3. The method for preparing the polypyrrole-urea-formaldehyde resin cross-linked photothermal energy storage phase change microcapsules according to claim 1, characterized in that The melting point of the phase change material in step 1 is between -10°C and 50°C.

4. The method for preparing the polypyrrole-urea-formaldehyde resin cross-linked photothermal energy storage phase change microcapsules according to claim 1, characterized in that In step 1, the mass ratio of phase change material to activated carbon is 10:

1.

5. The method for preparing the polypyrrole-urea-formaldehyde resin cross-linked photothermal energy storage phase change microcapsules according to claim 1, characterized in that The surfactant in step 2 is polyvinyl pyrrolidone, Tween-80 or Span-80.

6. The method for preparing the polypyrrole-urea-formaldehyde resin cross-linked photothermal energy storage phase change microcapsules according to claim 1, characterized in that The mass ratio of the pretreated phase change material in step 2 to the purified pyrrole monomer is (3~5):

1.

7. The method for preparing the polypyrrole-urea-formaldehyde resin cross-linked photothermal energy storage phase change microcapsules according to claim 1, characterized in that In step 3, the reaction time is 2 to 2.5 hours under stirring at 10 to 15°C.

8. The method for preparing the polypyrrole-urea-formaldehyde resin cross-linked photothermal energy storage phase change microcapsules according to claim 1, characterized in that In step 4, the reaction solution was heated to 50° C. and the cross-linking reaction was continued for 1 hour.

9. The method for preparing the polypyrrole-urea-formaldehyde resin cross-linked photothermal energy storage phase change microcapsules according to claim 1, characterized in that In step 5, the concentration of hydroquinone in the mixed solution of hydroquinone and triethanolamine is 0.2wt%~0.4wt%, and the concentration of triethanolamine is 0.4wt%~0.6wt%.

10. Application of the polypyrrole-urea-formaldehyde resin cross-linked photothermal energy storage phase change microcapsules prepared as claimed in claim 1, characterized in that The polypyrrole-urea-formaldehyde resin cross-linked photothermal energy storage phase change microcapsules are used as wall coatings, vehicle coatings, textile coatings, thermal conductive media or composite membranes in membrane components.

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