CN114316922B - Composite phase change material for packaging lauric acid and preparation method thereof - Google Patents
Composite phase change material for packaging lauric acid and preparation method thereof Download PDFInfo
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- CN114316922B CN114316922B CN202210034790.XA CN202210034790A CN114316922B CN 114316922 B CN114316922 B CN 114316922B CN 202210034790 A CN202210034790 A CN 202210034790A CN 114316922 B CN114316922 B CN 114316922B
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Abstract
The invention relates to the technical field of phase change materials and discloses a composite phase change material for packaging lauric acid and a preparation method thereof, wherein the composite phase change material comprises aerogel which is formed by crosslinking and has a mutually communicated three-dimensional pore structure, and lauric acid packaged in the aerogel which has the mutually communicated three-dimensional pore structure; the aerogel with the mutually communicated three-dimensional porous structure is formed by crosslinking a poplar wadding carbon sheet under the action of a crosslinking agent; the cross-linking agent is polyvinyl alcohol aqueous solution. The poplar wadding carbon sheet is a polydopamine modified poplar wadding carbon sheet. According to the invention, the poplar batting carbon sheet/polyvinyl alcohol composite phase-change material modified by the polydopamine encapsulated with lauric acid is prepared by utilizing poplar batting, the materials involved in the preparation process are cheap and easy to obtain, and have no harm to the environment, so that the problems of high preparation cost and complex preparation process of the traditional graphene aerogel can be effectively solved, the preparation method has the capabilities of industrial production and practical application, and provides a new idea for biomass application.
Description
Technical Field
The invention relates to the technical field of phase change materials, and discloses a composite phase change material for packaging lauric acid and a preparation method thereof.
Background
Along with the rapid development of economy and the continuous improvement of people's life, the demand for energy is gradually increased, and the world population is increased, so that the energy shortage is further aggravated. The energy sources at present mainly depend on fossil fuels such as coal and petroleum, but the fossil fuels are non-renewable energy sources, and the use of the fossil fuels inevitably causes environmental pollution, so the development of clean and renewable energy sources is an effective method for solving the problem.
Solar energy is used as renewable clean energy, has the advantages of no regional limitation, large energy, no pollution and the like, but the intermittence and randomness of the solar energy often lead to unbalanced supply and demand and low utilization efficiency, so the solar energy is captured and stored as heat energy to be the key for effectively utilizing the solar energy. Phase change materials store a large amount of solar energy in the form of latent heat and release again at a constant phase change temperature, and are a promising energy storage medium. Among the phase change materials studied, solid-liquid phase change materials have received attention because of their large latent heat capacity, constant phase change temperature, small volume change, and repeatable storage/release characteristics. However, the solid-liquid phase change material inevitably leaks in the phase change process, so that the heat storage performance of the phase change material is affected, and the service life of the phase change material is shortened.
To cope with these problems, the aerogel with ultra-low density, ultra-high porosity and large specific surface area has been widely used for the synthesis of shape-stable phase change materials, wherein graphene aerogel is concerned by researchers due to its good thermal conductivity and good absorption of visible light in the range of 400-760 nm, but its large-scale industrial production and application are limited due to its high manufacturing cost and complicated manufacturing process. Based on the above, it is necessary to prepare a phase change material that is inexpensive and environmentally friendly.
Disclosure of Invention
The invention aims to overcome the defects and provide a composite phase change material for packaging lauric acid and a preparation method thereof.
In order to achieve the above purpose, the invention is implemented according to the following technical scheme:
a composite phase change material for encapsulating lauric acid, the composite phase change material comprises aerogel which is formed by crosslinking and has a three-dimensional pore structure which is mutually communicated, and lauric acid which is encapsulated in the aerogel which has the three-dimensional pore structure which is mutually communicated;
the aerogel with the mutually communicated three-dimensional porous structure is formed by crosslinking a poplar wadding carbon sheet under the action of a crosslinking agent;
the cross-linking agent is polyvinyl alcohol aqueous solution.
The pores of the aerogel having the interconnected three-dimensional porous structure are interconnected. The macroscopic shape of the aerogel with the interconnected three-dimensional porous structure can be regulated and controlled by a mould.
Preferably, the poplar wadding carbon sheet is a polydopamine modified poplar wadding carbon sheet.
Preferably, the concentration of the polyvinyl alcohol aqueous solution is 5g/L to 20g/L.
Preferably, the mass ratio of the polydopamine modified poplar wadding carbon sheet to the polyvinyl alcohol is 5-9:1-5.
Preferably, the lauric acid is automatically encapsulated in an aerogel having a three-dimensional cellular structure in communication with each other.
The invention also discloses a preparation method of the composite phase change material for packaging lauric acid, which comprises the following steps:
s1, repeatedly cleaning poplar wool with deionized water and absolute ethyl alcohol, and drying in an oven at 70 ℃ for 18 hours to obtain dried poplar wool;
s2, annealing the dried poplar wool for 2 hours at 800 ℃ in an argon atmosphere to obtain an annealed Yang Xutan pipe; the heating rate in the annealing process is 5 ℃/min;
s3, carrying out ultrasonic crushing treatment on the annealed Yang Xutan pipe in absolute ethyl alcohol, and drying after the treatment is finished to obtain a poplar wadding carbon sheet;
s4, dispersing the poplar wadding carbon sheets in tris-HCl buffer solution, adding dopamine hydrochloride, stirring in an open mode, and performing centrifugal separation and drying to obtain polydopamine modified poplar wadding carbon sheets;
s5, adding the polydopamine modified poplar wadding carbon sheet into a polyvinyl alcohol aqueous solution, stirring at room temperature, pouring into a mold, freezing in a refrigerator for 2 hours, and then freeze-drying to obtain aerogel with a mutually communicated three-dimensional porous structure; stirring at room temperature for 24h, and freeze-drying for 18h by using a freeze dryer;
s6, placing lauric acid in a beaker, heating and melting in a water bath at 50 ℃, then placing aerogel with a mutually communicated three-dimensional porous structure, and automatically completing encapsulation of lauric acid due to capillary force and surface tension of the aerogel with the mutually communicated three-dimensional porous structure to obtain the polydopamine modified poplar wadding carbon sheet/polyvinyl alcohol composite phase change material for encapsulating lauric acid.
Preferably, in the step S4, the ph=8.5 of the tris-HCl buffer solution, and the volume ratio of the mass of the poplar-like carbon sheet to the tris-HCl buffer solution is 1g:200 mL-400 mL; the mass ratio of the poplar wadding carbon sheet to the dopamine hydrochloride is 1:4; the stirring time was 24h.
Preferably, in the step S5, the concentration of the polyvinyl alcohol aqueous solution is 5g/L to 20g/L; the mass ratio of the poly-dopa amine modified poplar wadding carbon sheet to the polyvinyl alcohol is 5-9:1-5.
The invention has the action principle that:
the polydopamine-modified poplar-wadding carbon sheet/polyvinyl alcohol composite phase-change material for encapsulating lauric acid, which is prepared by the invention, takes polydopamine-modified poplar-wadding carbon sheet/polyvinyl alcohol (aerogel with a three-dimensional pore structure which is mutually communicated) as a supporting material. According to the invention, dopamine hydrochloride is adopted to modify the poplar wadding carbon sheet, so that the surface of the polydopamine modified poplar wadding carbon sheet has rich oxygen-containing functional groups (hydroxyl groups); and mixing and stirring the polydopamine modified poplar batting carbon sheet with the polyvinyl alcohol aqueous solution serving as a cross-linking agent for 24 hours at normal temperature, enabling the polydopamine modified poplar batting carbon sheet to self-assemble through the action of hydrogen bond force in the stirring process to form a microscopic three-dimensional network structure, and finally freeze-drying the stirred suspension liquid to obtain the aerogel with the macroscopic-shape-adjustable mutually-communicated three-dimensional pore structure. Because of the unique interconnected three-dimensional porous structure, the aerogel has the characteristics of low density, high porosity, large specific surface area and the like, and has higher lauric acid encapsulation rate.
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, the poplar-wadding carbon sheet/polyvinyl alcohol composite phase-change material modified by polydopamine for encapsulating lauric acid is prepared by utilizing poplar wadding, the prepared aerogel with the mutually communicated three-dimensional porous structure has a large encapsulation amount for lauric acid, about 3g of lauric acid can be encapsulated by about 0.27g of aerogel, the encapsulation rate can reach 88.1% at most, and the phase-change material can still maintain good mechanical and chemical stability after repeated heat absorption and release cycles. The materials involved in the preparation process are cheap and easy to obtain, have no harm to the environment, can effectively solve the problems of high preparation cost and complex preparation process of the traditional graphene aerogel, have the capabilities of industrial production and practical application, and provide a new idea for biomass application.
Drawings
FIG. 1 is a schematic diagram of an aerogel having interconnected three-dimensional pore structures according to example 1 of the present invention;
FIG. 2 is a Scanning Electron Microscope (SEM) image of an aerogel having interconnected three-dimensional cellular structures obtained in step 7 according to example 1 of the present invention;
FIG. 3 is a graph showing the mass change of the aerogel having interconnected three-dimensional pore structures obtained in example 1 and example 2 of the present invention before and after encapsulation of lauric acid;
FIG. 4 is a graph showing the comparison of thermal stability of pure lauric acid, the polydopamine modified poplar-batting carbon sheet/polyvinyl alcohol composite phase change material encapsulated with lauric acid of example 1, and the polydopamine modified poplar-batting carbon sheet/polyvinyl alcohol composite phase change material encapsulated with lauric acid of example 2;
fig. 5 is a graph showing the heat absorption and release properties of pure lauric acid, the polydopamine modified poplar-batting carbon sheet/polyvinyl alcohol composite phase change material encapsulated with lauric acid of example 1, and the polydopamine modified poplar-batting carbon sheet/polyvinyl alcohol composite phase change material encapsulated with lauric acid of example 2;
FIG. 6 is a Differential Scanning Calorimeter (DSC) performance graph of pure lauric acid, polydopamine modified poplar batting carbon sheet/polyvinyl alcohol composite phase change material encapsulated with lauric acid of example 1, polydopamine modified poplar batting carbon sheet/polyvinyl alcohol composite phase change material encapsulated with lauric acid of example 2;
FIG. 7 is an XRD spectrum of pure lauric acid, polydopamine modified poplar batting carbon sheet/polyvinyl alcohol composite phase change material encapsulated with lauric acid of example 1;
fig. 8 is a graph of thermal conductivity of pure lauric acid, the polydopamine modified poplar-batting carbon sheet/polyvinyl alcohol composite phase change material encapsulated with lauric acid of example 1, and the polydopamine modified poplar-batting carbon sheet/polyvinyl alcohol composite phase change material encapsulated with lauric acid of example 2.
Detailed Description
The invention is further described in terms of specific examples, illustrative examples and illustrations of which are provided herein to illustrate the invention, but are not to be construed as limiting the invention.
Example 1
A composite phase change material for encapsulating lauric acid, the composite phase change material comprises aerogel which is formed by crosslinking and has a three-dimensional pore structure which is mutually communicated, and lauric acid which is encapsulated in the aerogel which has the three-dimensional pore structure which is mutually communicated; the aerogel with the mutually communicated three-dimensional porous structure is formed by crosslinking poplar wadding carbon sheets under the action of a polyethylene alcohol aqueous solution; the poplar wadding carbon sheet is a polydopamine modified poplar wadding carbon sheet.
The preparation method of the composite phase change material for encapsulating lauric acid comprises the following steps:
1) Washing the collected poplar wadding with deionized water and absolute ethyl alcohol for a plurality of times, and then drying the poplar wadding in a drying oven at 70 ℃ for 18 hours to obtain dried poplar wadding;
2) Putting the dried poplar wadding into a tube furnace, and annealing for 2 hours at 800 ℃ under argon atmosphere to obtain an annealed Yang Xutan tube; the temperature rising rate is 5 ℃/min;
3) Carrying out ultrasonic crushing treatment on the annealed Yang Xutan pipe in absolute ethyl alcohol for 6 hours, and drying to obtain a poplar wadding carbon sheet;
4) 1.22114g of a tris reagent is weighed and dissolved in 980mL of deionized water, the pH value is adjusted to 8.5 by using 1mol/L hydrochloric acid prepared in advance (measured in real time by using a pH meter), and then the solution is transferred to a 1000mL volumetric flask to be fixed in volume by using deionized water, so as to obtain tris-HCl buffer solution with the pH value of 8.5;
5) Putting 0.5g of the poplar wadding carbon sheet obtained in the step 3) into 150mL of tris-HCl buffer solution, stirring for 10min to uniformly disperse, then adding 2g of dopamine hydrochloride into the solution, vigorously stirring for 24h in an open manner, centrifuging, and drying to obtain a polydopamine modified poplar wadding carbon sheet;
6) Adding 0.06g of polyvinyl alcohol solid into 4mL of water, heating to melt the polyvinyl alcohol solid in an oil bath at 95 ℃, and then cooling to room temperature to obtain a polyvinyl alcohol aqueous solution;
7) Adding 0.24g of the polydopamine modified poplar-based carbon sheet in the step 5) into the polyvinyl alcohol aqueous solution (15 g/L) in the step 6), stirring for 24 hours at room temperature, pouring into a mould, putting into a refrigerator, freezing for 2 hours, taking out, putting into a freeze dryer, and freeze-drying for 18 hours to obtain the aerogel with the mutually communicated three-dimensional porous structure.
8) Placing lauric acid in a beaker, heating and melting in a water bath at 50 ℃, then placing aerogel with a mutually communicated three-dimensional porous structure, and automatically completing encapsulation of lauric acid in a few minutes due to capillary force and surface tension of the aerogel with the mutually communicated three-dimensional porous structure to obtain the polydopamine modified poplar wadding carbon sheet/polyvinyl alcohol composite phase-change material encapsulated with lauric acid, wherein the composite phase-change material is denoted as LA@PCP 8:2.
As shown in fig. 1, in example 1 of the present invention, the product of the aerogel having the interconnected three-dimensional pore structure obtained in step 7 is shown. The aerogel obtained in example 1, which has a three-dimensional interconnected pore structure, can be stably placed on the grass of the dog tail, so that the aerogel prepared by the invention has light weight and low density.
As shown in fig. 2, a Scanning Electron Microscope (SEM) image of the aerogel having the interconnected three-dimensional pore structure obtained in step 7 in example 1 of the present invention is shown. From the figure, the polydopamine modified poplar wadding carbon sheet is assembled under the action of the cross-linking agent polyvinyl alcohol to form a mutually communicated three-dimensional porous structure, and the pore diameter is about 1-6 mu m.
As shown in fig. 3, fig. 3a is a mass of 0.2740g of the aerogel having the interconnected three-dimensional pore structure prepared in example 1; FIG. 3b shows the mass of the aerogel prepared in example 1 having interconnected three-dimensional pore structure after encapsulation of lauric acid, 3.2406g.
In example 1, the aerogel having a three-dimensional pore structure interconnected and obtained in step 7 had a mass of 0.2740g and a volume of 8.36cm 3 Calculated to have a bulk density of 0.03277g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the After the step 8, the mass of the polydopamine modified poplar-batting carbon sheet/polyvinyl alcohol composite phase-change material (LA@PCP 8:2) for encapsulating lauric acid obtained in the embodiment is 3.2406g, and the encapsulation mass of lauric acid in the embodiment is 2.9666g.
As shown in fig. 4, fig. 4a is a solid pure lauric acid (denoted LA) of mass 3.2104g in the shape of a cylinder at 25 ℃;65 ℃ and 0s;65 ℃ for 30s;65 ℃ and 60s;50 ℃ for 10min; state diagram under five temperature time conditions.
FIG. 4b shows a polydopamine modified poplar batting carbon sheet/polyvinyl alcohol composite phase change material (LA@PCP 8:2) with a mass of 3.2406g, a cylindrical shape, encapsulating lauric acid obtained in example 1 at 25 ℃;65 ℃ and 0s;65 ℃ for 30s;65 ℃ and 60s;50 ℃ for 10min; state diagram under five temperature time conditions.
The morphology stability of the pure lauric acid and the polydopamine modified poplar wadding carbon sheet/polyvinyl alcohol composite phase change material encapsulated with lauric acid obtained in the example 1 can be maintained in a room temperature environment (25 ℃). When the temperature was raised to 65 ℃ and above the phase transition temperature of lauric acid, the polydopamine modified poplar-batting carbon sheet/polyvinyl alcohol composite phase change material obtained in example 1 was heated at 65 ℃ for 60s without obvious leakage (fig. 3 b), but pure lauric acid started to melt when heated at 65 ℃ for 30s, and was converted from solid to liquid (fig. 3 a). Pure lauric acid and the polydopamine modified poplar wadding carbon sheet/polyvinyl alcohol composite phase change material encapsulated with lauric acid obtained in example 1 are heated for 10min at 50 ℃, and the mass of the remaining solids is weighed respectively. Pure lauric acid melted severely, changing the solid mass from 3.2104g to 1.032g. The quality of the polydopamine modified poplar-batting carbon sheet/polyvinyl alcohol composite phase-change material with lauric acid encapsulated obtained in example 1 is hardly changed from 3.2406g to 3.108g.
As shown in fig. 7, the XRD spectrum of the polydopamine modified poplar-wadded carbon sheet/polyvinyl alcohol composite phase-change material of pure lauric acid and encapsulated lauric acid of example 1 is shown. Example 1 a polydopamine modified poplar batting carbon sheet/polyvinyl alcohol composite phase change material (la@pcp8:2) encapsulated with lauric acid shows diffraction characteristic peaks similar to that of pure Lauric Acid (LA), which indicates that lauric acid has better chemical compatibility with polydopamine modified poplar batting carbon sheet/polyvinyl alcohol aerogel. Furthermore, the degree of crystallization of lauric acid in the aerogel pores is not affected.
Example 2
The preparation method of the composite phase change material for encapsulating lauric acid comprises the following steps:
1) Washing the collected poplar wadding with deionized water and absolute ethyl alcohol for a plurality of times, and then drying the poplar wadding in a drying oven at 70 ℃ for 18 hours to obtain dried poplar wadding;
2) Putting the dried poplar wadding into a tube furnace, and annealing for 2 hours at 800 ℃ under argon atmosphere to obtain an annealed Yang Xutan tube; the temperature rising rate is 5 ℃/min;
3) Carrying out ultrasonic crushing treatment on the annealed Yang Xutan pipe in absolute ethyl alcohol for 6 hours, and drying to obtain a poplar wadding carbon sheet;
4) 1.22114g of a tris reagent is weighed and dissolved in 980mL of deionized water, the pH value is adjusted to 8.5 by using 1mol/L hydrochloric acid prepared in advance (measured in real time by using a pH meter), and then the solution is transferred to a 1000mL volumetric flask to be fixed in volume by using deionized water, so as to obtain tris-HCl buffer solution with the pH value of 8.5;
5) Putting 0.5g of the poplar wadding carbon sheet obtained in the step 3) into 150mL of tris-HCl buffer solution, stirring for 10min to uniformly disperse, then adding 2g of dopamine hydrochloride into the solution, vigorously stirring for 24h in an open manner, centrifuging, and drying to obtain a polydopamine modified poplar wadding carbon sheet;
6) Adding 0.03g of polyvinyl alcohol solid into 3.75mL of water, heating to melt the polyvinyl alcohol solid in an oil bath at the temperature of 95 ℃, and cooling to room temperature to obtain a polyvinyl alcohol aqueous solution;
7) Adding 0.27g of the polydopamine modified poplar-based carbon sheet in the step 5) into the polyvinyl alcohol aqueous solution (8 g/L) in the step 6), stirring for 24 hours at room temperature, pouring into a mould, putting into a refrigerator, freezing for 2 hours, taking out, putting into a freeze dryer, and freeze-drying for 18 hours to obtain the aerogel with the mutually communicated three-dimensional porous structure.
8) Placing lauric acid in a beaker, heating and melting in a water bath at 50 ℃, then placing aerogel with a mutually communicated three-dimensional porous structure, automatically completing encapsulation of lauric acid in a few minutes by the aerogel with the mutually communicated three-dimensional porous structure, and obtaining the polydopamine modified poplar wadding carbon sheet/polyvinyl alcohol composite phase-change material encapsulated with lauric acid, which is denoted as LA@PCP 9:1.
As shown in fig. 3, fig. 3c is a mass of 0.2645g of the aerogel having the interconnected three-dimensional pore structure prepared in example 2; FIG. 3d shows the mass of the aerogel prepared in example 2 having interconnected three-dimensional pore structure after encapsulation of lauric acid, 3.1600g.
In example 2, the mass of the aerogel having the interconnected three-dimensional pore-like structure obtained in step 7 was 0.2645g; after the step 8, the mass of the polydopamine modified poplar-batting carbon sheet/polyvinyl alcohol composite phase-change material (LA@PCP 9:1) for encapsulating lauric acid obtained in the embodiment is 3.1600g, and the encapsulation mass of lauric acid in the embodiment is 2.8955g.
As shown in fig. 4, fig. 4c is a graph of the polydopamine modified poplar-batting carbon sheet/polyethylene alcohol composite phase change material (la@pcp 9:1) encapsulated with lauric acid of example 2 at 25 ℃;65 ℃ and 0s;65 ℃ for 30s;65 ℃ and 60s;50 ℃ for 10min; state diagram under five temperature time conditions.
At 25 ℃; the example 2 lauric acid-encapsulated poly (dopa-modified poplar-batting carbon sheet)/polyvinyl alcohol composite phase change material can maintain shape stability at 65 ℃,30s and 65 ℃ under 60s conditions, and has no obvious leakage. When the polydopamine modified poplar wadding carbon sheet/polyvinyl alcohol composite phase-change material encapsulated with lauric acid in example 2 is heated at 50 ℃ for 10min, no obvious leakage exists, and compared with the mass before heating, the mass is reduced by 0.0687g.
As shown in fig. 5, fig. 5a shows that the temperature rising rate of the polydopamine modified poplar-wadded carbon sheet/polyvinyl alcohol composite phase-change material (la@pcp 9:1) encapsulated with lauric acid of example 2 > the temperature rising rate of the polydopamine modified poplar-wadded carbon sheet/polyvinyl alcohol composite phase-change material (la@pcp 8:2) encapsulated with lauric acid of example 1 > the temperature rising rate of pure Lauric Acid (LA) compared with pure lauric acid, the heat conductivity of the composite phase-change material encapsulated with lauric acid is improved.
Fig. 5a is a graph of endothermic performance and fig. 5b is a graph of exothermic performance.
As shown in fig. 6, the differential scanning heat (DSC) performance graphs of pure Lauric Acid (LA), the polydopamine modified poplar-wadded carbon sheet/polyvinyl alcohol composite phase-change material (la@pcp 8:2) encapsulated with lauric acid of example 1, and the polydopamine modified poplar-wadded carbon sheet/polyvinyl alcohol composite phase-change material (la@pcp 9:1) encapsulated with lauric acid of example 2 are shown.
As shown in Table 1, the data analysis of Differential Scanning Calorimeter (DSC) performance graphs of pure lauric acid, the polydopamine modified poplar-wadding carbon sheet/polyvinyl alcohol composite phase change material encapsulated with lauric acid of example 1 and the polydopamine modified poplar-wadding carbon sheet/polyvinyl alcohol composite phase change material encapsulated with lauric acid of example 2 are shown.
TABLE 1
As can be seen from Table 1, the melting phase transition enthalpy of pure Lauric Acid (LA) is 195.6J/g, while the melting phase transition enthalpy of the composite phase change material (LA@PCP 8:2) with the mass ratio of polydopamine modified poplar-batting carbon sheet to polyvinyl alcohol of 8:2 in example 1 is 172.5J/g, and the encapsulation efficiency of the composite phase change material is 88.1% compared with the existing phase change material by a formula.
As shown in fig. 8, the thermal conductivity of the polydopamine modified poplar-batting carbon sheet/polyvinyl alcohol composite phase-change material encapsulated with lauric acid is obviously improved, the thermal conductivities of the polydopamine modified poplar-batting carbon sheet/polyvinyl alcohol composite phase-change material (la@pcp 8:2) encapsulated with lauric acid of example 1 and the polydopamine modified poplar-batting carbon sheet/polyvinyl alcohol composite phase-change material (la@pcp 9:1) encapsulated with lauric acid of example 2 are respectively 0.325W/m·k and 0.373W/m·k, and compared with pure lauric acid (0.246W/m·k), the thermal conductivities are respectively improved by 32.1% and 51.6%.
Example 3
The preparation method of the composite phase change material for encapsulating lauric acid comprises the following steps:
1) Washing the collected poplar wadding with deionized water and absolute ethyl alcohol for a plurality of times, and then drying the poplar wadding in a drying oven at 70 ℃ for 18 hours to obtain dried poplar wadding;
2) Putting the dried poplar wadding into a tube furnace, and annealing for 2 hours at 800 ℃ under argon atmosphere to obtain an annealed Yang Xutan tube; the temperature rising rate is 5 ℃/min;
3) Carrying out ultrasonic crushing treatment on the annealed Yang Xutan pipe in absolute ethyl alcohol for 6 hours, and drying to obtain a poplar wadding carbon sheet;
4) 1.22114g of a tris reagent is weighed and dissolved in 980mL of deionized water, the pH value is adjusted to 8.5 by using 1mol/L hydrochloric acid prepared in advance (measured in real time by using a pH meter), and then the solution is transferred to a 1000mL volumetric flask to be fixed in volume by using deionized water, so as to obtain tris-HCl buffer solution with the pH value of 8.5;
5) Putting 0.5g of the poplar wadding carbon sheet obtained in the step 3) into 150mL of tris-HCl buffer solution, stirring for 10min to uniformly disperse, then adding 2g of dopamine hydrochloride into the solution, vigorously stirring for 24h in an open manner, centrifuging, and drying to obtain a polydopamine modified poplar wadding carbon sheet;
6) Adding 0.06g of polyvinyl alcohol solid into 6mL of water, heating to melt the polyvinyl alcohol solid in an oil bath at 95 ℃, and then cooling to room temperature to obtain a polyvinyl alcohol aqueous solution;
7) Adding 0.24g of the polydopamine modified poplar-based carbon sheet in the step 5) into the polyvinyl alcohol aqueous solution (10 g/L) in the step 6), stirring for 24 hours at room temperature, pouring into a mould, putting into a refrigerator, freezing for 2 hours, taking out, putting into a freeze dryer, and freeze-drying for 18 hours to obtain the aerogel with the mutually communicated three-dimensional porous structure.
8) Placing lauric acid in a beaker, heating and melting in a water bath at 50 ℃, then placing aerogel with a mutually communicated three-dimensional porous structure, and automatically completing encapsulation of lauric acid within a few minutes by the aerogel with the mutually communicated three-dimensional porous structure to obtain the polydopamine modified poplar wadding carbon sheet/polyvinyl alcohol composite phase change material encapsulated with lauric acid.
Example 4
The preparation method of the composite phase change material for encapsulating lauric acid comprises the following steps:
1) Washing the collected poplar wadding with deionized water and absolute ethyl alcohol for a plurality of times, and then drying the poplar wadding in a drying oven at 70 ℃ for 18 hours to obtain dried poplar wadding;
2) Putting the dried poplar wadding into a tube furnace, and annealing for 2 hours at 800 ℃ under argon atmosphere to obtain an annealed Yang Xutan tube; the temperature rising rate is 5 ℃/min;
3) Carrying out ultrasonic crushing treatment on the annealed Yang Xutan pipe in absolute ethyl alcohol for 6 hours, and drying to obtain a poplar wadding carbon sheet;
4) 1.22114g of a tris reagent is weighed and dissolved in 980mL of deionized water, the pH value is adjusted to 8.5 by using 1mol/L hydrochloric acid prepared in advance (measured in real time by using a pH meter), and then the solution is transferred to a 1000mL volumetric flask to be fixed in volume by using deionized water, so as to obtain tris-HCl buffer solution with the pH value of 8.5;
5) Putting 0.5g of the poplar wadding carbon sheet obtained in the step 3) into 150mL of tris-HCl buffer solution, stirring for 10min to uniformly disperse, then adding 2g of dopamine hydrochloride into the solution, vigorously stirring for 24h in an open manner, centrifuging, and drying to obtain a polydopamine modified poplar wadding carbon sheet;
6) Adding 0.045g of polyvinyl alcohol solid into 4.5mL of water, heating to melt the polyvinyl alcohol solid in an oil bath at 95 ℃, and then cooling to room temperature to obtain a polyvinyl alcohol aqueous solution;
7) Adding 0.255g of the polydopamine modified poplar-based carbon sheet in the step 5) into the polyvinyl alcohol aqueous solution (10 g/L) in the step 6), stirring for 24 hours at room temperature, pouring into a mould, putting into a refrigerator, freezing for 2 hours, taking out, putting into a freeze dryer, and freeze-drying for 18 hours to obtain the aerogel with the mutually communicated three-dimensional porous structure.
8) Placing lauric acid in a beaker, heating and melting in a water bath at 50 ℃, then placing aerogel with a mutually communicated three-dimensional porous structure, and automatically completing encapsulation of lauric acid within a few minutes by the aerogel with the mutually communicated three-dimensional porous structure to obtain the polydopamine modified poplar wadding carbon sheet/polyvinyl alcohol composite phase change material encapsulated with lauric acid.
The technical scheme of the invention is not limited to the specific embodiment, and all technical modifications made according to the technical scheme of the invention fall within the protection scope of the invention.
Claims (4)
1. A composite phase change material encapsulating lauric acid, characterized in that: the composite phase change material comprises aerogel with a mutually communicated three-dimensional porous structure formed by crosslinking and lauric acid encapsulated in the aerogel with the mutually communicated three-dimensional porous structure;
the aerogel with the mutually communicated three-dimensional porous structure is formed by crosslinking a poplar wadding carbon sheet under the action of a crosslinking agent;
the cross-linking agent is polyvinyl alcohol aqueous solution;
the poplar wadding carbon sheet is a polydopamine modified poplar wadding carbon sheet;
the concentration of the polyvinyl alcohol aqueous solution is 5 g/L-20 g/L;
the mass ratio of the polydopamine modified poplar wadding carbon sheet to the polyvinyl alcohol is 5-9:1-5;
the lauric acid is automatically encapsulated in aerogel with a three-dimensional pore structure which is mutually communicated.
2. The method for preparing the lauric acid-encapsulated composite phase change material according to claim 1, wherein: the method comprises the following steps:
s1, cleaning poplar wadding, and drying to obtain dried poplar wadding;
s2, annealing the dried poplar wool for 2 hours at 800 ℃ in an argon atmosphere to obtain an annealed Yang Xutan pipe;
s3, carrying out ultrasonic crushing treatment on the annealed Yang Xutan pipe in absolute ethyl alcohol, and drying after the treatment is finished to obtain a poplar wadding carbon sheet;
s4, dispersing the poplar wadding carbon sheets in tris-HCl buffer solution, adding dopamine hydrochloride, centrifuging after stirring in an open mode, and drying to obtain polydopamine modified poplar wadding carbon sheets;
s5, adding the polydopamine modified poplar wadding carbon sheet into a polyvinyl alcohol aqueous solution, stirring at room temperature, pouring into a mold, freezing in a refrigerator for 2 hours, and then freeze-drying to obtain aerogel with a mutually communicated three-dimensional porous structure;
s6, placing lauric acid in a beaker, heating and melting in a water bath at 50 ℃, and then placing aerogel with a mutually communicated three-dimensional pore structure, wherein the aerogel with the mutually communicated three-dimensional pore structure automatically encapsulates lauric acid, so that the polydopamine modified poplar wadding carbon sheet/polyvinyl alcohol composite phase change material encapsulated with lauric acid is obtained.
3. The method for preparing the lauric acid-encapsulated composite phase change material according to claim 2, wherein: in the step S4, the pH=8.5 of the tris-HCl buffer solution, and the volume ratio of the mass of the poplar-flocked carbon sheet to the tris-HCl buffer solution is 1g:200 mL-400 mL; the mass ratio of the poplar wadding carbon sheet to the dopamine hydrochloride is 1:4; the stirring time was 24h.
4. A method for preparing a composite phase change material encapsulating lauric acid according to claim 3, wherein: in the step S5, the concentration of the polyvinyl alcohol aqueous solution is 5g/L to 20g/L; the mass ratio of the polydopamine modified poplar wadding carbon sheet to the polyvinyl alcohol is 5-9:1-5.
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