1. A self-healing hydrogel phase-change material is characterized by comprising an inorganic phase-change material, a hydrogel base material, a nucleating agent and a crystal form changing agent, wherein the hydrogel base material comprises a monomer with a self-healing function, a salt-resistant monomer, a main cross-linking agent, an auxiliary cross-linking agent, an initiator and deionized water,

the inorganic phase change material is selected from inorganic hydrated salts,

the nucleating agent is at least one of sodium tetraborate, borax, glycerol, sodium citrate dihydrate, sodium molybdate dihydrate and disodium hydrogen phosphate dodecahydrate, the content of the nucleating agent is 3-5 percent of that of the inorganic phase-change material,

the crystal form modifier is selected from sodium hexametaphosphate, the content of the crystal form modifier is 0.1 percent of the content of the inorganic phase-change material,

the monomer with the self-healing function is at least one of sodium acrylate, chitosan, acrylamide, polylysine and polyethyleneimine, the content of the monomer with the self-healing function is 3-13% of that of the inorganic phase change material,

the salt-resistant monomer is selected from sodium alginate or hydroxyethyl methacrylate, the content of the salt-resistant monomer is 0.2 percent of the content of the inorganic phase-change material,

the main cross-linking agent is selected from N, N' -methylene bisacrylamide, the content of the main cross-linking agent is 0.5 percent of the content of the inorganic phase-change material,

the secondary cross-linking agent is selected from calcium sulfate dihydrate, the content of the secondary cross-linking agent is 1 percent of the content of the inorganic phase-change material,

the initiator is selected from thermal initiator or photoinitiator, the initiator content is 1.5-3% of the inorganic phase-change material content,

the content of the deionized water is 10% of the content of the inorganic phase-change material.

2. A self-healing hydrogel phase change material according to claim 1, wherein the inorganic hydrated salt is one or more of sodium sulfate decahydrate, sodium acetate trihydrate, disodium hydrogen phosphate dodecahydrate, sodium carbonate decahydrate, and calcium chloride hexahydrate.

3. A self-healing hydrogel phase change material according to claim 1, wherein the initiator is at least one selected from the group consisting of ammonium persulfate, potassium persulfate, photoinitiator 1173, photoinitiator 184, and photoinitiator 907.

4. A method for preparing the self-healing hydrogel phase change material according to any one of claims 1 to 3, comprising the steps of:

(1) keeping the inorganic hydrated salt under sealed heating at the water bath temperature, and starting stirring after heating until phase separation phenomenon occurs and crystals appear on the bottom layer;

(2) sequentially adding a nucleating agent, a crystal form changing agent and a monomer with a self-healing function into the molten liquid, keeping the temperature of the water bath closed, heating, and stirring until the solution is uniformly dispersed;

(3) pouring the main cross-linking agent, the salt-resistant monomer and the auxiliary cross-linking agent into the solution in sequence, keeping the water bath temperature for heating, and stirring until the solution is uniformly dispersed;

(4) dissolving a proper amount of initiator in a proper amount of deionized water, dropwise adding the initiator into the uniformly stirred mixed solution, keeping the heating temperature of the water bath unchanged during the process, continuously stirring, gradually crosslinking the solution into gel, and finally forming a compact three-dimensional reticular gel structure.

5. The method for preparing a self-healing hydrogel phase change material according to claim 4, wherein the stirring rate in step (4) is 600-800 r/min.

Background

Phase Change Materials (PCMs) are energy source materials that absorb or release latent heat to the outside by undergoing a phase change at a certain temperature, thereby achieving the purpose of temperature regulation. The process of changing the material property of the phase-change material is accompanied with the storage and the release of energy, the utilization rate of energy can be effectively improved, and the characteristic of the phase-change material gains higher attention for the phase-change material in the current society with more prominent energy problems.

The phase change material can be divided into an organic phase change material and an inorganic phase change material, and can also be divided into a hydrated salt phase change material and a waxy phase change material. The inorganic hydrated salt phase-change material is widely applied in various fields due to the advantages of large phase-change latent heat, low price, nonflammability, safety, nontoxicity and the like, but the phase-change material has the defects of supercooling, poor system stability and the like in the phase-change process.

The hydrogel is an ideal environment-friendly high-molecular polymer, has high water content, can effectively prevent water leakage, has a simple preparation method and low cost, wraps the phase-change material with the hydrogel to encapsulate the phase-change material, and can play a role in protecting the phase-change material with water in the hydrogel. However, in practical application, the hydrogel prepared by using the traditional organic cross-linking agent has poor mechanical properties due to weak cross-linking effect, is broken under small deformation or pressure, cannot protect the phase-change material, and how to improve the mechanical properties of the hydrogel is the key of the application.

Disclosure of Invention

The invention aims to provide a self-healing hydrogel phase-change material which can self-heal after being damaged by external force extrusion.

The invention also aims to provide a preparation method of the self-healing hydrogel phase-change material.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

in one aspect, the invention provides a self-healing hydrogel phase-change material, which comprises an inorganic phase-change material, a hydrogel base material, a nucleating agent and a crystal form changing agent, wherein the hydrogel base material comprises a monomer with a self-healing function, a salt-resistant monomer, a main cross-linking agent, a secondary cross-linking agent, an initiator and deionized water, wherein,

the inorganic phase change material is selected from inorganic hydrated salts,

the nucleating agent is at least one of sodium tetraborate, borax, glycerol, sodium citrate dihydrate, sodium molybdate dihydrate and disodium hydrogen phosphate dodecahydrate, the content of the nucleating agent is 3-5 percent of that of the inorganic phase-change material,

the crystal form modifier is selected from sodium hexametaphosphate, the content of the crystal form modifier is 0.1 percent of the content of the inorganic phase-change material,

the monomer with the self-healing function is selected from at least one of sodium acrylate, chitosan, acrylamide, polylysine and polyethyleneimine, and the content of the monomer with the self-healing function is 3% -13% of that of the inorganic phase change material;

the salt-resistant monomer is selected from sodium alginate, hydroxyethyl methacrylate and the like, the content of the salt-resistant monomer is 0.2 percent of the content of the inorganic phase-change material,

the main cross-linking agent is selected from N, N' -methylene bisacrylamide, the content of the main cross-linking agent is 0.5 percent of the content of the inorganic phase-change material,

the secondary cross-linking agent is selected from calcium sulfate dihydrate, the content of the secondary cross-linking agent is 1 percent of the content of the inorganic phase-change material,

the initiator is at least one of ammonium persulfate, potassium persulfate, a photoinitiator 1173, a photoinitiator 184 and a photoinitiator 907, the content of the initiator is 1.5-3% of that of the inorganic phase-change material,

the content of the deionized water is 10% of the content of the inorganic phase-change material.

Preferably, the inorganic hydrated salt is one or more of sodium sulfate decahydrate, sodium acetate trihydrate, disodium hydrogen phosphate dodecahydrate, sodium carbonate decahydrate and calcium chloride hexahydrate.

On the other hand, the invention also provides a preparation method of the self-healing hydrogel phase-change material, which comprises the following steps:

(1) keeping the inorganic hydrated salt under sealed heating at the water bath temperature, and starting stirring after heating until phase separation phenomenon occurs and crystals appear on the bottom layer;

(2) sequentially adding a nucleating agent, a crystal form changing agent and a monomer with a self-healing function into the molten liquid, keeping the temperature of the water bath closed, heating, and stirring until the solution is uniformly dispersed;

(3) pouring the main cross-linking agent, the salt-resistant monomer and the auxiliary cross-linking agent into the solution in sequence, keeping the water bath temperature for heating, and stirring until the solution is uniformly dispersed;

(4) dissolving a proper amount of initiator in a proper amount of deionized water, dropwise adding the initiator into the uniformly stirred mixed solution, keeping the heating temperature of the water bath unchanged during the process, continuously stirring, gradually crosslinking the solution into gel, and finally forming a compact three-dimensional reticular gel structure.

Preferably, the stirring rate in step (4) is 600-800 r/min.

The hydrogel is self-healing by crosslinking and self-healing by using the monomers with hydrogen bonds, so that the hydrogel can self-heal without being affected by external force even under the condition of fracture and disconnection, the main material wrapped by the hydrogel is an inorganic salt material, the price is low, the commercialization feasibility is realized, and the hydrogel not only has a phase change function, but also can self-heal.

Compared with the prior art, the invention has the following beneficial effects:

1) the hydrated inorganic salt phase-change material obtained by the invention has higher thermal conductivity and has less influence on other (such as enthalpy value) of the phase-change material. The inorganic phase-change material has the characteristics of high phase-change latent heat, good heat-conducting property, large energy storage density, low price and mass production. The inorganic phase change material has large supercooling degree, and the development prospect is hindered only when the phase separation is serious. The invention adds proper amount of nucleating agent and crystal form changing agent, not only eliminates supercooling degree, but also prolongs phase change platform, the added crosslinking monomer also makes sodium sulfate decahydrate and other additives disperse uniformly, phase separation phenomenon is eliminated, and gel well wraps sodium sulfate decahydrate, so enthalpy value is not reduced obviously.

2) The hydrogel disclosed by the invention not only has a phase change effect, but also has a self-healing property, and because the added crosslinking monomer contains other structures with self-healing properties such as hydrogen bonds or imine bonds, and the other structures with self-healing properties are crosslinked into a three-dimensional network structure through an initiator to form gel with a certain shape and strength, even if the gel is damaged and broken, the gel can still self-heal without depending on the action of external force and restore to the original shape.

3) The hydrogel is an environment-friendly material, has no pollution to the environment, and is non-toxic and harmless to human bodies. And the price is low, the product has commercial mass production value, and has profound significance in the field of biological human body.

4) The hydrogel of the invention has extremely good conductivity, and the crystalline inorganic salt material is found to be conductive in a molten state and has very small resistance, thus having wide prospects in the field of electronic devices.

Drawings

FIG. 1 is a self-healing image of a sodium sulfate decahydrate (3% sodium acrylate) self-healing hydrogel phase change material of example 1;

FIG. 2 is a self-healing image of a self-healing hydrogel phase change material of example 2 disodium hydrogen phosphate dodecahydrate (3% sodium acrylate);

FIG. 3 is a self-healing image of the self-healing hydrogel phase change material of sodium acetate trihydrate (3% chitosan) of example 3;

FIG. 4 is a self-healing image of a sodium sulfate decahydrate (3% acrylamide) self-healing hydrogel phase change material of example 4;

FIG. 5 is a self-healing image of the self-healing hydrogel phase change material of example 5 disodium hydrogen phosphate dodecahydrate (3% acrylamide).

Detailed Description

The invention is described in further detail below with reference to the figures and specific examples. The scope of the present invention is not limited by the following examples.

Example 1

(1) Weighing 40g of sodium sulfate decahydrate, and melting in a water bath at 40 ℃ under a sealed condition;

(2) weighing 1.6g of borax, 0.04g of sodium hexametaphosphate and 1.2g of sodium acrylate, sequentially pouring into a molten sodium sulfate decahydrate solution, keeping the water bath temperature at 40 ℃, heating in a sealed manner, and stirring until the solution is uniformly dispersed;

(3) adding 0.2g N, N-methylene bisacrylamide, 0.08g of sodium alginate and 0.4g of calcium sulfate dihydrate into the dispersion liquid obtained in the step (2), keeping the water bath temperature at 40 ℃, heating, and stirring until the solution is uniformly dispersed (continuously stirring for about 20 minutes until the solution is uniformly stirred and no layering occurs);

(4) pouring 0.6g of initiator ammonium persulfate into 4g of deionized water, fully dissolving, and dropwise adding ammonium persulfate initiator solution while keeping the water bath heating temperature unchanged, wherein the rotation speed of a stirrer is 600 r/min;

(5) after the ammonium persulfate initiator solution is added dropwise, the temperature of the water bath is kept at 40 ℃ and the rotating speed of 600r/min, the solution is slowly crosslinked into gel state until the stirrer cannot rotate, and the experimental process is finished.

The phase-change temperature of the self-healing hydrogel phase-change material prepared by the embodiment is 34.60 ℃, the latent heat of phase change is-138.29J/g, and the thermal conductivity is 0.5023W/(m.K).

Fig. 1 is a self-healing image of a sodium sulfate decahydrate (3% sodium acrylate) self-healing hydrogel phase change material.

Example 2

(1) Weighing 40g of disodium hydrogen phosphate dodecahydrate, and melting in a water bath at 45 ℃ under a sealed condition;

(2) weighing 1.6g of sodium citrate dihydrate, 0.04g of sodium hexametaphosphate and 1.2g of sodium acrylate, sequentially pouring into a molten disodium hydrogen phosphate dodecahydrate solution, keeping the water bath temperature at 45 ℃, heating, and stirring until the solution is uniformly dispersed;

(3) adding 0.2g N, N-methylene bisacrylamide, 0.08g of sodium alginate and 0.4g of calcium sulfate dihydrate into the dispersion liquid obtained in the step (2), keeping the water bath temperature at 45 ℃, heating, and stirring until the solution is uniformly dispersed (continuously stirring for about 20 minutes until the solution is uniformly stirred and no layering occurs);

(4) pouring 0.6g of initiator potassium persulfate into 4g of deionized water, fully dissolving, and dropwise adding a potassium persulfate initiator solution while keeping the water bath heating temperature unchanged, wherein the rotation speed of a stirrer is 600 r/min;

(5) after the potassium persulfate initiator solution is dripped, the temperature of the water bath is kept at 45 ℃ and the rotating speed of 600r/min, the solution is slowly crosslinked into gel until the stirrer cannot rotate, and the experimental process is finished.

The phase-change temperature of the self-healing hydrogel phase-change material prepared in the embodiment is 35.5 ℃, the latent heat of phase change is-170.23J/g, and the thermal conductivity is 0.4876W/(m.K).

Fig. 2 is a self-healing image of a disodium hydrogen phosphate dodecahydrate (3% sodium acrylate) self-healing hydrogel phase change material.

Example 3

(1) Weighing 40g of sodium acetate trihydrate, and melting under the sealed condition of a water bath at 58 ℃;

(2) weighing 2g of disodium hydrogen phosphate dodecahydrate, 0.04g of sodium hexametaphosphate and 1.2g of chitosan, sequentially pouring into a molten sodium acetate trihydrate solution, keeping the water bath temperature at 58 ℃, heating, and stirring until the solution is uniformly dispersed;

(3) adding 0.2g N, N-methylene bisacrylamide, 0.08g of sodium alginate and 0.4g of calcium sulfate dihydrate into the dispersion liquid obtained in the step (2), keeping the water bath temperature at 58 ℃, heating, and stirring until the solution is uniformly dispersed (continuously stirring for about 20 minutes until the solution is uniformly stirred and no layering occurs);

(4) dropwise adding 1.2g of photoinitiator 1173 into the solution, then adding 4g of deionized water, keeping the heating temperature of the water bath unchanged, setting the rotation speed of a stirrer at 800r/min, and irradiating by using ultraviolet light;

(5) and keeping the water bath heating at 58 ℃ and the stirring speed of 800r/min, and slowly crosslinking the solution into gel until the stirrer cannot rotate, thus finishing the experimental process.

The phase-change temperature of the self-healing hydrogel phase-change material prepared by the embodiment is 58.10 ℃, the latent heat of phase change is-210.23J/g, and the thermal conductivity is 0.5834W/(m.K).

Fig. 3 is a self-healing image of a sodium acetate trihydrate (3% chitosan) self-healing hydrogel phase change material.

Example 4

(1) Weighing 40g of sodium sulfate decahydrate, and melting in a water bath at 40 ℃ under a sealed condition;

(2) weighing 1.6g of borax, 0.04g of sodium hexametaphosphate and 1.2g of acrylamide, sequentially pouring into a molten sodium sulfate decahydrate solution, keeping the water bath temperature at 40 ℃, heating, and stirring until the solution is uniformly dispersed;

(3) adding 0.2g N, N-methylene bisacrylamide, 0.08g of sodium alginate and 0.4g of calcium sulfate dihydrate into the dispersion liquid obtained in the step (2), keeping the water bath temperature at 40 ℃, heating, and stirring until the solution is uniformly dispersed (continuously stirring for about 20 minutes until the solution is uniformly stirred and no layering occurs);

(4) sequentially dripping 1.2g of photoinitiator 1173 into the solution, then adding 4g of deionized water, keeping the heating temperature of the water bath unchanged during the process, stirring at the stirring speed of 800r/min by a stirrer, and irradiating by using ultraviolet light with the wavelength of 365 nm;

(5) keeping the temperature of the water bath at 40 ℃ and the stirring speed of 800r/min, slowly crosslinking the solution into gel until the stirrer cannot rotate, and ending the experimental process.

The phase-change temperature of the self-healing hydrogel phase-change material prepared by the embodiment is 34.20 ℃, the latent heat of phase change is-121.24J/g, and the thermal conductivity is 0.5135W/(m.K).

Fig. 4 is a self-healing image of a sodium sulfate decahydrate (3% acrylamide) self-healing hydrogel phase change material.

Example 5

(1) Weighing 40g of disodium hydrogen phosphate dodecahydrate, and melting in a water bath at 45 ℃ under a sealed condition;

(2) weighing 1.2g of sodium citrate dihydrate, 0.04g of sodium hexametaphosphate and 1.2g of acrylamide, sequentially pouring into a molten disodium hydrogen phosphate dodecahydrate solution, keeping the water bath temperature at 45 ℃, heating, and stirring until the solution is uniformly dispersed;

(3) adding 0.2g N, N-methylene bisacrylamide, 0.08g of sodium alginate and 0.4g of calcium sulfate dihydrate into the dispersion liquid obtained in the step (2), keeping the water bath temperature at 45 ℃, heating, and stirring until the solution is uniformly dispersed (continuously stirring for about 20 minutes until the solution is uniformly stirred and no layering occurs);

(4) pouring 0.6g of initiator potassium persulfate into 4g of deionized water, fully dissolving, and dropwise adding a potassium persulfate initiator solution while keeping the water bath heating temperature unchanged, wherein the rotation speed of a stirrer is 600 r/min;

(5) after the potassium persulfate initiator solution is dripped, the temperature of the water bath is kept at 45 ℃ and the stirring speed of 600r/min, the solution is slowly crosslinked into gel until the stirrer cannot rotate, and the experimental process is finished.

The phase-change temperature of the self-healing hydrogel phase-change material prepared by the embodiment is 35.61 ℃, the latent heat of phase change is-175.20J/g, and the thermal conductivity is 0.5023W/(m.K).

Fig. 5 is a self-healing image of a disodium hydrogen phosphate dodecahydrate (3% acrylamide) self-healing hydrogel phase change material.

Performance test experiment

And (3) taking the self-healing inorganic phase change gel material of the same amount of the embodiment 1-5, performing a self-healing experiment under a tensile testing machine, and comparing the tensile force before and after stretching, wherein the self-healing rate is the ratio of the tensile force of the phase change material after self-healing to the tensile force of the original phase change material. The results are shown in Table 1.

Table 1 self-healing rates of the examples

Example 1

Example 2

Example 3

Example 4

Example 5

Example 6

Self-healing Rate (%)

96.2％

93.5％

94.2％

95.1％

94.8％

93.6％

According to the results of the performance test analysis, the inorganic self-healing phase-change material provided by the embodiment of the invention has a good self-healing function and can be self-repaired to be the same as the original one. The inorganic phase change material has the advantages of low price, high heat storage density, nonflammability and the like. The inorganic post-self-healing phase change material provided by the invention can be applied to more suitable temperature scenes, and is a phase change material which is environment-friendly, economical, safe, nontoxic and wide in application range.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be construed as the protection scope of the present invention.