CN108485608B - Method for reducing supercooling degree of normal alkane energy storage material microcapsule - Google Patents
Method for reducing supercooling degree of normal alkane energy storage material microcapsule Download PDFInfo
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- 239000003094 microcapsule Substances 0.000 title claims abstract description 114
- 238000004146 energy storage Methods 0.000 title claims abstract description 108
- 239000011232 storage material Substances 0.000 title claims abstract description 92
- 238000004781 supercooling Methods 0.000 title claims abstract description 67
- 238000000034 method Methods 0.000 title claims abstract description 46
- 150000001335 aliphatic alkanes Chemical class 0.000 title claims abstract description 37
- 239000002667 nucleating agent Substances 0.000 claims abstract description 60
- 229920000877 Melamine resin Polymers 0.000 claims abstract description 55
- 239000002775 capsule Substances 0.000 claims abstract description 50
- 239000004640 Melamine resin Substances 0.000 claims abstract description 34
- 239000002131 composite material Substances 0.000 claims abstract description 33
- 239000013078 crystal Substances 0.000 claims abstract description 20
- 229920001046 Nanocellulose Polymers 0.000 claims abstract description 18
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 13
- 238000010899 nucleation Methods 0.000 claims abstract description 12
- 230000006911 nucleation Effects 0.000 claims abstract description 12
- 230000000694 effects Effects 0.000 claims abstract description 8
- 125000004432 carbon atom Chemical group C* 0.000 claims abstract description 7
- 238000003756 stirring Methods 0.000 claims description 48
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 42
- 238000002156 mixing Methods 0.000 claims description 28
- 238000006243 chemical reaction Methods 0.000 claims description 24
- SXRSQZLOMIGNAQ-UHFFFAOYSA-N Glutaraldehyde Chemical compound O=CCCCC=O SXRSQZLOMIGNAQ-UHFFFAOYSA-N 0.000 claims description 21
- 239000000839 emulsion Substances 0.000 claims description 21
- JDSHMPZPIAZGSV-UHFFFAOYSA-N melamine Chemical compound NC1=NC(N)=NC(N)=N1 JDSHMPZPIAZGSV-UHFFFAOYSA-N 0.000 claims description 21
- 239000000463 material Substances 0.000 claims description 15
- 239000012153 distilled water Substances 0.000 claims description 14
- 230000007935 neutral effect Effects 0.000 claims description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 14
- 238000001816 cooling Methods 0.000 claims description 12
- 238000006116 polymerization reaction Methods 0.000 claims description 11
- 238000002360 preparation method Methods 0.000 claims description 9
- 238000010438 heat treatment Methods 0.000 claims description 7
- 230000000087 stabilizing effect Effects 0.000 claims description 7
- 239000002994 raw material Substances 0.000 claims 1
- 238000002425 crystallisation Methods 0.000 abstract description 37
- 230000008025 crystallization Effects 0.000 abstract description 37
- 230000008859 change Effects 0.000 abstract description 9
- 239000003795 chemical substances by application Substances 0.000 abstract description 5
- 150000001875 compounds Chemical class 0.000 abstract description 3
- 238000013329 compounding Methods 0.000 abstract 1
- 239000011162 core material Substances 0.000 description 34
- RZJRJXONCZWCBN-UHFFFAOYSA-N octadecane Chemical compound CCCCCCCCCCCCCCCCCC RZJRJXONCZWCBN-UHFFFAOYSA-N 0.000 description 30
- CBFCDTFDPHXCNY-UHFFFAOYSA-N icosane Chemical compound CCCCCCCCCCCCCCCCCCCC CBFCDTFDPHXCNY-UHFFFAOYSA-N 0.000 description 28
- HOWGUJZVBDQJKV-UHFFFAOYSA-N docosane Chemical compound CCCCCCCCCCCCCCCCCCCCCC HOWGUJZVBDQJKV-UHFFFAOYSA-N 0.000 description 22
- DCAYPVUWAIABOU-UHFFFAOYSA-N hexadecane Chemical compound CCCCCCCCCCCCCCCC DCAYPVUWAIABOU-UHFFFAOYSA-N 0.000 description 16
- VAMFXQBUQXONLZ-UHFFFAOYSA-N n-alpha-eicosene Natural products CCCCCCCCCCCCCCCCCCC=C VAMFXQBUQXONLZ-UHFFFAOYSA-N 0.000 description 14
- LQERIDTXQFOHKA-UHFFFAOYSA-N nonadecane Chemical compound CCCCCCCCCCCCCCCCCCC LQERIDTXQFOHKA-UHFFFAOYSA-N 0.000 description 8
- 239000012782 phase change material Substances 0.000 description 8
- 239000002245 particle Substances 0.000 description 7
- 239000000306 component Substances 0.000 description 6
- NDJKXXJCMXVBJW-UHFFFAOYSA-N heptadecane Chemical compound CCCCCCCCCCCCCCCCC NDJKXXJCMXVBJW-UHFFFAOYSA-N 0.000 description 6
- 238000001514 detection method Methods 0.000 description 5
- 150000001721 carbon Chemical group 0.000 description 4
- 238000004132 cross linking Methods 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- FIGVVZUWCLSUEI-UHFFFAOYSA-N tricosane Chemical compound CCCCCCCCCCCCCCCCCCCCCCC FIGVVZUWCLSUEI-UHFFFAOYSA-N 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 239000002105 nanoparticle Substances 0.000 description 3
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 230000033228 biological regulation Effects 0.000 description 2
- 230000002401 inhibitory effect Effects 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- OVHHHVAVHBHXAK-UHFFFAOYSA-N n,n-diethylprop-2-enamide Chemical compound CCN(CC)C(=O)C=C OVHHHVAVHBHXAK-UHFFFAOYSA-N 0.000 description 2
- QNILTEGFHQSKFF-UHFFFAOYSA-N n-propan-2-ylprop-2-enamide Chemical compound CC(C)NC(=O)C=C QNILTEGFHQSKFF-UHFFFAOYSA-N 0.000 description 2
- 229920000128 polypyrrole Polymers 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 229920002678 cellulose Polymers 0.000 description 1
- 239000001913 cellulose Substances 0.000 description 1
- 239000007957 coemulsifier Substances 0.000 description 1
- 239000008358 core component Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 230000008014 freezing Effects 0.000 description 1
- 238000007710 freezing Methods 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 239000003112 inhibitor Substances 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K5/00—Heat-transfer, heat-exchange or heat-storage materials, e.g. refrigerants; Materials for the production of heat or cold by chemical reactions other than by combustion
- C09K5/02—Materials undergoing a change of physical state when used
- C09K5/06—Materials undergoing a change of physical state when used the change of state being from liquid to solid or vice versa
- C09K5/063—Materials absorbing or liberating heat during crystallisation; Heat storage materials
Abstract
The invention provides a method for reducing supercooling degree of n-alkane energy storage material microcapsules, which is characterized by comprising the following steps of: the method comprises the steps of preparing a composite capsule core mixed system, preparing a melamine resin prepolymer, preparing an O/W system and preparing an energy storage and temperature adjustment microcapsule. The invention selects two nucleating agents for compounding, namely selects the same compound with the carbon atom number higher than (n + 1) - (n + 2) of the phase change agent as the nucleating agent of homogeneous nucleation, and combines the heterogeneous nucleation of the nanocellulose crystal at the same time, thereby greatly reducing the supercooling degree of the normal alkane energy storage material microcapsule through the mutual combination of the two nucleating effects. Compared with the prior art, the supercooling degree of the normal alkane energy storage material microcapsule prepared by the invention is reduced by 3.6-5.0 ℃, and basically the theoretical crystallization temperature difference of the normal alkane energy storage material microcapsule with the normal alkane energy storage material microcapsule is kept to be not much.
Description
Technical Field
The invention relates to the technical field of energy storage and temperature regulation microcapsules, in particular to a technical method for reducing the supercooling degree of normal alkane energy storage material microcapsules.
Background
Supercooling means the difference between the theoretical crystallization temperature and the actually given crystallization site temperature, and is a temperature difference. The theoretical crystallization temperature is known and the actual crystallization temperature needs to be determined to give a temperature difference.
The supercooling crystallization of the energy storage material microcapsules is a ubiquitous physical phenomenon, mainly because heterogeneous nucleating agents in each capsule are less and less along with the reduction of the capsule particle size, so that heterogeneous nucleating and crystallization are difficult, and mainly homogeneous nucleating and crystallization are used as main materials, and supercooling crystallization enables heat stored in fibers to be released at a lower temperature or a wider temperature range, so that the temperature regulation function is reduced or lost.
The method for inhibiting supercooling of the phase-change material is mainly to add a nucleating agent to promote heterogeneous nucleation and crystallization of the phase-change material, wherein the commonly used nucleating agent comprises high-carbon-atom fatty alcohol, inorganic substances, nano particles and the like. However, the addition of the nucleating agent reduces the content of the phase-change material in the microcapsule, and further decreases with the increase of the addition amount; when high-carbon-atom fatty alcohol (hydroxyl has hydrophilicity) and sodium chloride (has demulsification property) are used as nucleating agents, the microcapsule phase-change material is easy to agglomerate; inorganic nanoparticles commonly added in the prior art are not ideal nucleating agents due to the consideration of poor intersolubility between the inorganic nanoparticles and core materials.
Chinese patent CN201510359606.9 discloses a phase change material microcapsule with low supercooling degree and a preparation method thereof. The technology is that at least one of N, N-diethyl acrylamide and N-isopropyl acrylamide is added into a capsule core component as a supercooling inhibitor, and a polymer is generated in the subsequent polymerization process to play a role of heterogeneous nucleation, so that the supercooling degree of the phase change material microcapsule is reduced. However, since N, N-diethylacrylamide and N-isopropylacrylamide act as water-soluble and co-emulsifier substances and some react with the capsule wall, the portion finally used as a heterogeneous nucleating agent is limited, and the exertion of the effect is limited.
Chinese patent CN 102876297A discloses a phase change material microcapsule with low supercooling degree and a preparation method thereof. The method takes polypyrrole as a heterogeneous nucleating agent, and the phase change material microcapsule with low supercooling degree is synthesized by a two-step polymerization method (one-step polymerization to form a capsule wall and two-step polymerization to form the polypyrrole), so that the preparation process is complex, and the problem of color change of the microcapsule is solved.
Chinese patent CN201410854746.9 discloses a double-layer wall material phase change microcapsule with controllable low supercooling degree and strength. In the patent technology, the inner wall material with low crosslinking degree is selected to improve the supercooling phenomenon of the phase change microcapsule, but the method for improving the supercooling phenomenon by using the inner wall material with low crosslinking degree is not feasible, and a crystallization nucleus is not provided, so that the microcapsule crystallization effect is seriously influenced.
Chinese patent CN201110235098.5 discloses an alkane microcapsule for inhibiting supercooling phase change and a preparation method and application thereof. In the patent technology, n-alkane with the carbon number of twenty-two to forty is used as the nucleating agent, although the nucleating agent and the phase change agent are the same compound, and the carbon number of the alkane nucleating agent is larger than that of the alkane phase change agent, the difference of the carbon numbers is too large, the difference of the freezing points of the two is too large, and the performance of the microcapsule is not ideal.
Disclosure of Invention
In view of the problems in the prior art, the invention aims to provide a method for reducing the supercooling degree of normal alkane energy storage material microcapsules, the supercooling crystallization phenomenon of the normal alkane energy storage material microcapsules prepared by the method is greatly improved, the supercooling degree of the normal alkane energy storage material microcapsules prepared by the invention is reduced by 3.6-5.0 ℃ compared with the prior art, and the preparation method is simple in process, convenient to operate and convenient for industrial implementation.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for reducing supercooling degree of n-alkane energy storage material microcapsules is characterized in that n-alkane energy storage materials (the number of carbon atoms is n, n is more than or equal to 16 and less than or equal to 22) and nucleating agents are used as composite capsule cores.
The nucleating agent comprises two substances, wherein one substance is an n-alkane material with 1-2 more carbon atoms than the phase change agent used for the capsule core, namely the nucleating agent is an n-alkane material with (n + 1) - (n + 2) carbon atoms; the other nucleating agent is a nano cellulose crystal with the diameter of 10-30 nm and the length of 50-100 nm.
Compared with the normal alkane phase-change energy storage material, the normal alkane material with high carbon atom number has higher crystallization temperature, but the difference of the carbon atom number is not large, so the crystallization temperatures of the normal alkane material and the normal alkane phase-change energy storage material cannot be greatly different, the normal alkane material with high carbon atom number preferentially crystallizes to serve as a crystal nucleus of the capsule core material in the crystallization process, and the supercooling degree of the normal alkane energy storage material microcapsule is greatly reduced by combining the two nucleation effects in view of the fact that the structural difference of the two materials is not large and is equivalent to homogeneous nucleation effect and combining the heterogeneous nucleation effect of the nanocellulose crystal.
The n-alkane energy storage material microcapsule prepared by the method comprises a composite capsule core and a capsule wall according to weight percentage, wherein the composite capsule core comprises 95.2-98.6% of n-alkane energy storage material, 1.0-3.0% of nucleating agent n-alkane material and 0.4-1.8% of nucleating agent nano-cellulose crystal according to weight percentage.
A method for reducing supercooling degree of n-alkane energy storage material microcapsules comprises the steps of preparing a composite capsule core mixed system, preparing melamine resin prepolymer, preparing an O/W system and preparing energy storage temperature adjustment microcapsules, and the specific scheme is as follows:
1. adding a composite capsule core (n-alkane energy storage material (the number of carbon atoms is n, 16 is less than or equal to n and less than or equal to 22), a nucleating agent n-alkane material ((n + 1) - (n + 2)) and a nucleating agent nanocellulose crystal into a mixing kettle according to the mass ratio of (95.2-98.6) to (1.0-3.0) to (0.4-1.8)), stirring at the temperature of 35-50 ℃ and the stirring speed of 400-1000 rpm for 30-60 min, and uniformly mixing to prepare a composite capsule core mixing system.
2. Adding melamine, glutaraldehyde and a proper amount of distilled water into a reaction kettle with a thermometer, a stirring paddle and a condenser, wherein the ratio of the melamine to the glutaraldehyde is (3-6) to 1, the mass ratio of the total mass of the melamine and the glutaraldehyde to the distilled water is (1-4), adding sodium hydroxide to adjust the pH value to 8.0-9.5, heating to 80-90 ℃ for reaction, adding PVA after the solution becomes clear, reducing the temperature to 65-72 ℃, reacting at a constant temperature for 50-60 min, adjusting the pH value of the system to be neutral by using the sodium hydroxide, and reducing the temperature to 45-50 ℃ for later use, thereby preparing the melamine resin prepolymer.
3. And (3) mixing the composite capsule-core mixed system prepared in the step (1) with the effective components in the melamine resin prepolymer prepared in the step (2) according to the mass ratio of 50: 50-60: 40, and stirring at the temperature of 45-50 ℃ and the stirring speed of 2500-8000 rpm for 60-180 min to obtain an emulsion, so as to prepare an n-alkane energy storage material microcapsule emulsion system and form an O/W system.
4. Transferring the normal alkane energy storage material microcapsule emulsion system into a reaction kettle, fully stirring, stabilizing the temperature to 80-85 ℃, adjusting the pH to 5.5-6.5, reacting for 30-40 min to ensure that the flexible melamine resin prepolymer is crosslinked to prepare the energy storage and temperature adjustment microcapsule taking the normal alkane energy storage material as a capsule core and the melamine resin as a capsule wall, adjusting the pH to be neutral after polymerization, naturally cooling, stopping stirring, and obtaining the normal alkane energy storage material microcapsule, wherein the supercooling degree of the microcapsule is greatly reduced, and the particle size D90 is not more than 2.128 mu m.
The invention has the beneficial effects that:
(1) the invention selects the same compound with the carbon atom number higher than (n + 1) - (n + 2) of the phase change agent as the nucleating agent of homogeneous nucleation, combines the heterogeneous nucleation of the nanocellulose crystal, and greatly reduces the supercooling degree of the normal alkane energy storage material microcapsule by the mutual combination of the two nucleation. Compared with the prior art, the supercooling degree of the normal alkane energy storage material microcapsule prepared by the invention is reduced by 3.6-5.0 ℃, and basically the theoretical crystallization temperature difference of the normal alkane energy storage material microcapsule with the normal alkane energy storage material microcapsule is kept to be not much.
(2) The n-alkane energy storage material microcapsule prepared by the invention has the supercooling degree of 0.7-2.1 ℃; compared with the normal alkane energy storage material microcapsule prepared by independently adding the nucleating agent normal alkane materials ((n + 1) - (n + 2)), the supercooling degree is reduced by 3.3-5 ℃; compared with the normal alkane energy storage material microcapsule without the nucleating agent, the supercooling degree is reduced by 6.9-12.7 ℃.
The present invention will be described in detail with reference to examples.
Detailed Description
The following description of the preferred embodiments of the present invention is provided for the purpose of illustration and description, and is in no way intended to limit the invention.
Example 1: method for reducing supercooling degree of normal alkane energy storage material microcapsule
The method comprises the following steps:
step 1, preparing a composite capsule core mixed system
Adding the composite capsule core (n-hexadecane, the nucleating agent n-heptadecane and the nucleating agent nanocellulose crystal in a mass ratio of 95.2:3.0: 1.8) into a mixing kettle, stirring for 30min at the temperature of 35 ℃ and the stirring speed of 1000rpm, and uniformly mixing to prepare a composite capsule core mixing system.
Step 2, preparing melamine resin prepolymer
Adding melamine, glutaraldehyde and a proper amount of distilled water into a reaction kettle with a thermometer, a stirring paddle and a condenser, wherein the ratio of the melamine to the glutaraldehyde is 3:1, the mass ratio of the total mass of the melamine and the glutaraldehyde to the distilled water is 1:1, adding sodium hydroxide to adjust the pH value to 8.0, heating to 80 ℃ to perform reaction, adding PVA after the solution becomes clear, reducing the temperature to 65 ℃, performing constant-temperature reaction for 60min, adjusting the pH value of the system to be neutral by using the sodium hydroxide, and cooling to 45 ℃ for later use to prepare a melamine resin prepolymer.
Step 3, preparing an O/W system
And (3) mixing the composite capsule core mixed system prepared in the step (1) with the effective components in the melamine resin prepolymer prepared in the step (2) according to the mass ratio of 50:50, and stirring at the stirring speed of 2500rpm at the temperature of 45 ℃ for 180min to obtain an emulsion, so as to prepare an n-hexadecane energy storage material microcapsule emulsion system, thereby forming an O/W system.
Step 4, preparing energy-storage temperature-regulating microcapsule
Transferring the n-hexadecane energy storage material microcapsule emulsion system into a reaction kettle, fully stirring, stabilizing the temperature to 80 ℃, adjusting the pH value to 5.5, reacting for 40min to ensure that the flexible melamine resin prepolymer is crosslinked, preparing the energy storage and temperature adjustment microcapsule taking the n-hexadecane energy storage material as a capsule core and the melamine resin as a capsule wall, adjusting the pH value to be neutral after polymerization, naturally cooling, stopping stirring, greatly reducing the supercooling degree of the microcapsule, and enabling the particle size D90 of the microcapsule to be 2.128 mu m.
The detection shows that the initial crystallization temperature of the n-hexadecane energy storage material is 16.7 ℃, the initial crystallization temperature of the n-hexadecane energy storage material microcapsule without the nucleating agent is 9.6 ℃, the supercooling degree is 7.7 ℃, the initial crystallization temperature of the n-hexadecane energy storage material microcapsule with the nucleating agent added independently is 11.6 ℃, the supercooling degree is 4.1 ℃, the initial crystallization temperature of the energy storage material microcapsule prepared by the method of the embodiment 1 is 15.9 ℃, and the supercooling degree is 0.8 ℃.
Therefore, the supercooling degree of the microcapsule (added with the nucleating agent n-heptadecane and the nucleating agent nanocellulose crystal) prepared by the method of example 1 is reduced by 3.3 ℃ compared with that of the n-hexadecane energy storage material microcapsule added with the nucleating agent n-heptadecane alone.
Example 2: method for reducing supercooling degree of normal alkane energy storage material microcapsule
The method comprises the following steps:
step 1, preparing a composite capsule core mixed system
Adding the composite capsule core (n-octadecane, the nucleating agent n-nonadecane and the nucleating agent nanocellulose crystal in a mass ratio of 96.5:2.3: 1.2) into a mixing kettle, stirring for 36min at the temperature of 38 ℃ and at the stirring speed of 816rpm, and uniformly mixing to prepare a composite capsule core mixing system.
Step 2, preparing melamine resin prepolymer
Adding melamine, glutaraldehyde and a proper amount of distilled water into a reaction kettle with a thermometer, a stirring paddle and a condenser, wherein the ratio of the melamine to the glutaraldehyde is 4:1, the mass ratio of the total mass of the melamine and the glutaraldehyde to the distilled water is 1:2, adding sodium hydroxide to adjust the pH value to 8.3, heating to 82 ℃ for reaction, adding PVA after the solution becomes clear, reducing the temperature to 68 ℃, reacting at constant temperature for 58min, adjusting the pH value of the system to be neutral by using the sodium hydroxide, and cooling to 47 ℃ for later use to prepare the melamine resin prepolymer.
Step 3, preparing an O/W system
And (3) mixing the composite capsule-core mixed system prepared in the step (1) with the effective components in the melamine resin prepolymer prepared in the step (2) according to the mass ratio of 55:45, and stirring at the temperature of 46 ℃ and the stirring speed of 3800rpm for 126min to obtain an emulsion, so as to prepare an n-alkane energy storage material microcapsule emulsion system and form an O/W system.
Step 4, preparing energy-storage temperature-regulating microcapsule
Transferring the n-octadecane energy storage material microcapsule emulsion system into a reaction kettle, fully stirring, stabilizing the temperature to 81 ℃, adjusting the pH value to 5.8, reacting for 38min, crosslinking the flexible melamine resin prepolymer, preparing the energy storage and temperature adjustment microcapsule taking the n-octadecane energy storage material as a capsule core and the melamine resin as a capsule wall, adjusting the pH value to be neutral after polymerization, naturally cooling, stopping stirring, greatly reducing the supercooling degree of the microcapsule, and enabling the particle size D90 of the microcapsule to be 2.116 mu m.
The detection shows that the initial crystallization temperature of the n-octadecane energy storage material is 25.5 ℃, the initial crystallization temperature of the n-octadecane energy storage material microcapsule without the nucleating agent is 16.8 ℃, and the supercooling degree is 8.7 ℃; the initial crystallization temperature of the n-octadecane energy storage material microcapsule with the nucleating agent n-nonadecane added independently is 20.8 ℃, and the supercooling degree is 4.7 ℃; the energy storage material microcapsule prepared by the method of the embodiment 2 has the initial crystallization temperature of 24.5 ℃ and the supercooling degree of 1.0 ℃;
therefore, the supercooling degree of the microcapsule prepared by the method of example 2 (the nucleating agent n-nonadecane and the nucleating agent nanocellulose crystal) is reduced by 3.7 ℃ compared with the n-octadecane energy storage material microcapsule with the nucleating agent n-nonadecane added alone.
Example 3: method for reducing supercooling degree of normal alkane energy storage material microcapsule
The method comprises the following steps:
step 1, preparing a composite capsule core-mixed system
Adding the composite capsule core (n-eicosane, the nucleating agent n-docosane and the nucleating agent nanocellulose crystal according to the mass ratio of 97.1: 1.8: 1.1) into a mixing kettle, stirring for 44min at the temperature of 43 ℃ and the stirring speed of 690rpm, and uniformly mixing to prepare a composite capsule core-mixing system.
Step 2, preparing melamine resin prepolymer
Adding melamine, glutaraldehyde and a proper amount of distilled water into a reaction kettle with a thermometer, a stirring paddle and a condenser, wherein the ratio of the melamine to the glutaraldehyde is 5:1, the mass ratio of the total mass of the melamine and the glutaraldehyde to the distilled water is 1:3, adding sodium hydroxide to adjust the pH value to 8.6, heating to 85 ℃ to perform reaction, adding PVA after the solution becomes clear, reducing the temperature to 70 ℃, performing constant-temperature reaction for 55min, adjusting the pH value of the system to be neutral by using the sodium hydroxide, and cooling to 48 ℃ for later use to prepare a melamine resin prepolymer.
Step 3, preparing an O/W system
And (3) mixing the composite capsule-core mixed system prepared in the step (1) with the effective components in the melamine resin prepolymer prepared in the step (2) according to the mass ratio of 58:42, and stirring at the temperature of 48 ℃ and the stirring speed of 5600rpm for 102min to obtain an emulsion, so as to prepare an n-alkane energy storage material microcapsule emulsion system, and form an O/W system.
Step 4, preparing energy-storage temperature-regulating microcapsule
Transferring the n-eicosane energy storage material microcapsule emulsion system into a reaction kettle, fully stirring, stabilizing the temperature to 82 ℃, adjusting the pH value to 6.2, reacting for 35min to ensure that the flexible melamine resin prepolymer is crosslinked, preparing the energy storage and temperature adjustment microcapsule taking the n-eicosane energy storage material as a capsule core and the melamine resin as a capsule wall, adjusting the pH value to be neutral after polymerization, naturally cooling and stopping stirring, and greatly reducing the supercooling degree of the microcapsule, wherein the particle size D90 of the microcapsule is 2.036 microns.
The detection shows that the initial crystallization temperature of the n-eicosane energy storage material microcapsule is 30.6 ℃, the initial crystallization temperature of the n-eicosane energy storage material microcapsule without the nucleating agent is 20.5 ℃, and the supercooling degree is 10.1 ℃; the initial crystallization temperature of the n-eicosane energy storage material microcapsule with the nucleating agent n-docosane added independently is 24.3 ℃, the supercooling degree is 6.3 ℃, the initial crystallization temperature of the n-eicosane energy storage material microcapsule prepared by the method of the embodiment 3 is 28.3 ℃, and the supercooling degree is 1.3 ℃;
therefore, the supercooling degree of the energy storage material microcapsule prepared by the method of example 3 (with the added nucleating agent n-docosane and the nucleating agent nanocellulose crystal) is reduced by 5.0 ℃ compared with the n-eicosane energy storage material microcapsule with the added nucleating agent n-docosane alone.
Example 4: method for reducing supercooling degree of normal alkane energy storage material microcapsule
The method comprises the following steps:
step 1, preparing a composite capsule core mixed system
Adding the composite capsule core (n-docosane, the nucleating agent n-tricosane and the nucleating agent nanocellulose crystal according to the mass ratio of 97.9:1.5: 0.6) into a mixing kettle, stirring for 53min at the temperature of 48 ℃ and the stirring speed of 555rpm, and uniformly mixing to prepare a composite capsule core mixing system.
Step 2, preparing melamine resin prepolymer
Adding melamine, glutaraldehyde and a proper amount of distilled water into a reaction kettle with a thermometer, a stirring paddle and a condenser, wherein the ratio of the melamine to the glutaraldehyde is 6:1, the mass ratio of the total mass of the melamine and the glutaraldehyde to the distilled water is 1:3, adding sodium hydroxide to adjust the pH value to 9.0, heating to 88 ℃ for reaction, adding PVA after the solution becomes clear, reducing the temperature to 71 ℃, carrying out constant-temperature reaction for 53min, adjusting the pH value of the system to be neutral by using the sodium hydroxide, and cooling to 49 ℃ for later use to prepare the melamine resin prepolymer.
Step 3, preparing an O/W system
And (3) mixing the composite capsule-core mixed system prepared in the step (1) with the effective components in the melamine resin prepolymer prepared in the step (2) according to the mass ratio of 60:40, and stirring at the temperature of 49 ℃ and the stirring speed of 7160rpm for 85min to obtain an emulsion, so as to prepare an n-alkane energy storage material microcapsule emulsion system, and form an O/W system.
Step 4, preparing energy-storage temperature-regulating microcapsule
Transferring the n-docosane energy storage material microcapsule emulsion system into a reaction kettle, fully stirring, stabilizing the temperature to 83 ℃, adjusting the pH value to 6.4, reacting for 33min to ensure that the flexible melamine resin prepolymer is crosslinked, preparing the energy storage and temperature adjustment microcapsule taking the n-docosane energy storage material as a capsule core and the melamine resin as a capsule wall, adjusting the pH value to be neutral after polymerization, naturally cooling, stopping stirring, greatly reducing the supercooling degree of the microcapsule, and ensuring that the particle size D90 of the microcapsule is 1.996 mu m.
The detection shows that the initial crystallization temperature of the n-docosane energy storage material is 44.4 ℃, the initial crystallization temperature of the n-docosane energy storage material microcapsule without the nucleating agent is 29.6 ℃, and the supercooling degree is 14.8 ℃; the initial crystallization temperature of the n-docosane energy storage material microcapsule with the nucleating agent n-tricosane added independently is 38.7 ℃, and the supercooling degree is 6.7 ℃;
the initial crystallization temperature of the n-eicosane energy storage material microcapsule prepared by the method of example 4 is 42.3 ℃, and the supercooling degree is 2.1 ℃;
therefore, the supercooling degree of the energy storage material microcapsule prepared by the method of example 4 (the nucleating agent n-eicosane and the nucleating agent nanocellulose crystal are added) and the n-docosane energy storage material microcapsule with the nucleating agent n-eicosane added alone is reduced by 4.6 ℃.
Example 5: method for reducing supercooling degree of normal alkane energy storage material microcapsule
The method comprises the following steps:
step 1, preparing a composite capsule core mixed system
Adding the composite capsule core (n-octadecane, the nucleating agent n-eicosane and the nucleating agent nanocellulose crystal in a mass ratio of 98.6:1.0: 0.4) into a mixing kettle, stirring at a temperature of 50 ℃ and a stirring speed of 400rpm for 60min, and uniformly mixing to prepare a composite capsule core mixing system.
Step 2, preparing melamine resin prepolymer
Adding melamine, glutaraldehyde and a proper amount of distilled water into a reaction kettle with a thermometer, a stirring paddle and a condenser, wherein the ratio of the melamine to the glutaraldehyde is 6:1, the mass ratio of the total mass of the melamine and the glutaraldehyde to the distilled water is 1:4, adding sodium hydroxide to adjust the pH value to 9.5, heating to 90 ℃ to perform reaction, adding PVA after the solution becomes clear, reducing the temperature to 72 ℃, performing constant-temperature reaction for 50min, adjusting the pH value of the system to be neutral by using the sodium hydroxide, and cooling to 50 ℃ for later use to prepare a melamine resin prepolymer.
Step 3, preparing an O/W system
And (3) mixing the composite capsule-core mixed system prepared in the step (1) with the effective components in the melamine resin prepolymer prepared in the step (2) according to the mass ratio of 60:40, and stirring at the temperature of 50 ℃ and the stirring speed of 8000rpm for 60min to obtain an emulsion, so as to prepare an n-alkane energy storage material microcapsule emulsion system and form an O/W system.
Step 4, preparing energy-storage temperature-regulating microcapsule
Transferring the n-octadecane energy storage material microcapsule emulsion system into a reaction kettle, fully stirring, stabilizing the temperature to 85 ℃, adjusting the pH value to 6.5, reacting for 30min, crosslinking the flexible melamine resin prepolymer, preparing the energy storage and temperature adjustment microcapsule taking the n-octadecane energy storage material as a capsule core and the melamine resin as a capsule wall, adjusting the pH value to be neutral after polymerization, naturally cooling, stopping stirring, greatly reducing the supercooling degree of the microcapsule, and enabling the particle size D90 of the microcapsule to be 2.085 mu m.
The detection shows that the initial crystallization temperature of the n-octadecane energy storage material is 25.5 ℃, the initial crystallization temperature of the n-octadecane energy storage material microcapsule without the nucleating agent is 16.8 ℃, and the supercooling degree is 8.7 ℃; the initial crystallization temperature of the n-octadecane energy storage material microcapsule with the nucleating agent n-eicosane added independently is 21.2 ℃, and the supercooling degree is 4.3 ℃; the n-octadecane energy storage material microcapsule prepared by the method of the embodiment 5 has the initial crystallization temperature of 24.8 ℃ and the supercooling degree of 0.7 ℃;
therefore, compared with the supercooling degree of the n-octadecane energy storage material microcapsule with the added nucleating agent n-eicosane and the added nucleating agent nanocellulose crystal, the energy storage material microcapsule prepared by the method in the embodiment 5 has the advantage that the supercooling degree is reduced by 3.6 ℃.
Unless otherwise specified, the proportions adopted in the invention are mass proportions; the adopted percentages are mass percentages.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still make modifications to the technical solutions described in the foregoing embodiments, and any modifications, equivalent substitutions, improvements, etc. within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (5)
1. A method for reducing the supercooling degree of microcapsules of n-alkane energy storage materials is characterized by comprising the following steps: the method comprises the steps of preparing a composite capsule core mixed system, preparing a melamine resin prepolymer, preparing an O/W system and preparing an energy storage and temperature adjustment microcapsule; the composite capsule core comprises the following raw materials in percentage by weight: 95.2-98.6% of normal alkane energy storage material, 1.0-3.0% of nucleating agent normal alkane material and 0.4-1.8% of nucleating agent nano cellulose crystal;
the carbon atom number of the normal alkane energy storage material is 16-22;
the carbon atom number of the n-alkane material is 1-2 more than that of the n-alkane energy storage material, and the homogeneous nucleation effect is achieved;
the diameter of the nano cellulose crystal is 10-30 nm, the length of the nano cellulose crystal is 50-100 nm, and the heterogeneous nucleation effect is achieved.
2. The method for reducing the supercooling degree of the n-alkane energy storage material microcapsule according to claim 1, wherein the method comprises the following steps: the preparation method comprises the steps of adding the composite capsule core into a mixing kettle, stirring for 30-60 min at the temperature of 35-50 ℃ and the stirring speed of 400-1000 rpm, and uniformly mixing to prepare the composite capsule core mixing system.
3. The method for reducing the supercooling degree of the n-alkane energy storage material microcapsule according to claim 1, wherein the method comprises the following steps: the preparation method comprises the steps of adding melamine, glutaraldehyde and distilled water, wherein the ratio of melamine to glutaraldehyde is 3: 1-6: 1, the mass ratio of the total mass of melamine and glutaraldehyde to the distilled water is 1: 1-1: 4, adding sodium hydroxide to adjust the pH to 8.0-9.5, heating to 80-90 ℃ for reaction, adding PVA after the solution becomes clear, reducing the temperature to 65-72 ℃, reacting at a constant temperature for 50-60 min, adjusting the pH of the system to be neutral by using sodium hydroxide, and reducing the temperature to 45-50 ℃ for later use.
4. The method for reducing the supercooling degree of the n-alkane energy storage material microcapsule according to claim 1, wherein the method comprises the following steps: the preparation method comprises the steps of preparing an O/W system, mixing the prepared composite capsule core mixed system and the prepared melamine resin prepolymer according to the mass ratio of 50: 50-60: 40, stirring at the temperature of 45-50 ℃ and the stirring speed of 2500-8000 rpm for 60-180 min to obtain an emulsion, and preparing an n-alkane energy storage material microcapsule emulsion system to form the O/W system.
5. The method for reducing the supercooling degree of the n-alkane energy storage material microcapsule according to claim 1, wherein the method comprises the following steps: the preparation method comprises the steps of transferring an O/W system of an n-alkane energy storage material microcapsule emulsion into a reaction kettle, fully stirring, stabilizing the temperature to 80-85 ℃, adjusting the pH to 5.5-6.5, reacting for 30-40 min, preparing energy storage and temperature adjustment microcapsules with an n-alkane energy storage material as a capsule core and melamine resin as a capsule wall, adjusting the pH to be neutral after polymerization, and naturally cooling and stopping stirring to obtain the n-alkane energy storage material microcapsules.
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