Preparation method of carbon fiber polyethylene glycol phase change composite material

Abstract

The present invention relates to a preparation method of a carbon fiber polyethylene glycol phase change composite material. The components of the carbon fiber polyethylene glycol phase change composite material and their mass parts are 100 parts of polyethylene glycol, 20 parts to 100 parts of calcium chloride, 20 parts to 100 parts of carbon fiber felt, and 0.5 parts to 3 parts of a coupling agent. The polyethylene glycol and calcium chloride can form a complex system, which can solve the problem of melting deformation of the phase change material to a certain extent. The surface treatment of the carbon fiber felt can improve the interface bonding problem between the carbon fiber and the phase change material, and improve the heat conduction path.

Description

Technical Field

[0001] The invention relates to the technical field of polymer thermal conductive phase change composite materials, in particular to a method for preparing a carbon fiber polyethylene glycol phase change composite material. Background Art

[0002] Polymer phase-change materials absorb heat by melting at high temperatures and release heat by recrystallizing when the surrounding temperature drops. During this process, the temperature of the phase-change material remains within a certain range (melting point), thereby ensuring the temperature stability of the surrounding environment. This property of polymer phase-change materials, which stabilizes the surrounding temperature within a certain range, has led to their application in electronic refrigeration, building heating / cooling (indoor temperature control), radiant floor heating, thermal switches, clothing, and other fields.

[0003] Commonly used polymer phase change materials and their melting points include eicosane (36°C), octadecane (28°C), 1-dodecanol (22°C), RT-22 (25.37°C), octadecanol (28.91°C), and RT27 (28.81°C). These polymer phase change materials absorb and release heat, ensuring the ambient temperature remains near the melting point of the phase change material. However, the thermal conductivity of these polymer phase change materials is 0.13 W / (m•K) for RT27, 0.17 W / (m•K) for octadecane, 0.26 W / (m•K) for RT25, 0.36 W / (m•K) for eicosane, 0.42 W / (m•K) for tetradecanol, and 0.48 W / (m•K) for capric acid. As can be seen from this, the bulk thermal conductivity of the aforementioned polymer phase change materials is generally low, which limits their application in rapid energy storage applications. Therefore, it is necessary to increase the thermal conductivity of polymer phase change materials to meet the needs of rapid energy storage.

[0004] Currently, the main method for improving the thermal conductivity of polymer phase change materials (PCMs) is to add highly thermally conductive fillers. Examples include metals (silver particles, copper particles, silver nanowires, copper nanowires), ceramics (boron nitride, aluminum nitride, aluminum oxide), and carbon materials (graphite, carbon nanofibers, carbon nanotubes, carbon black, and carbon fibers). High thermal conductivity in polymers is achieved primarily by allowing the filler to form highly conductive pathways within the polymer matrix. This involves using various methods to create a percolating network within the polymer, thereby causing a sudden change in the thermal conductivity of the polymer phase change material and achieving a higher thermal conductivity. However, traditional processes typically involve adding large amounts of fillers through blending to achieve percolation and improve the thermal conductivity of the material. However, excessively increasing the filler content increases the viscosity of the polymer phase change material, complicating processing and molding, while also reducing the thermal enthalpy (heat storage capacity) and other properties of the polymer itself. Therefore, the amount of filler added should be kept as low as possible to avoid compromising the processing and overall physical properties of the polymer phase change material. Through various methods, fillers can form a three-dimensional network structure in polymer phase change materials, thereby forming a highly thermally conductive pathway. Heat is quickly transferred through the three-dimensional network structure, achieving a low filler content and a high thermal conductivity coefficient. At present, methods for forming highly thermally conductive pathways in polymer composite materials, especially for fiber materials, mainly include freeze-drying orientation, electroplating molding, self-assembly molding, template method, etc. These methods can increase the thermal conductivity of polymer materials by several times or even dozens of times, and are a good way to quickly increase the thermal coefficient, and therefore have become a hot topic of research among scientists recently.

[0005] Since polymer phase change materials store energy by absorbing heat during melting, they are prone to shrinkage and flow deformation after melting, which brings difficulties to the application of phase change materials. Therefore, in order to reduce the problem of phase change material deformation, the phase change material needs to be confined. At present, the methods for improving the deformation of phase change materials mainly include microencapsulation, adsorption, cross-linking and other methods. For example, the phase change material is encapsulated in a polymer shell to form a microcapsule. The polymer shell can prevent the leakage of the phase change material. This method is called microencapsulation. For example, the method of using a porous material with a relatively large specific surface area to adsorb the phase change material and thus prevent the flow of the phase change material is called adsorption. The method of using chemical cross-linking to create cross-links between the molecular chains of the phase change material to prevent the material from deforming is called cross-linking. Therefore, preventing the melting deformation of phase change materials has also become a hot research topic among relevant scientists in recent years. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a carbon fiber polyethylene glycol phase change composite material with improved melt deformation and a 3D thermal conductive skeleton structure and a preparation method thereof.

[0007] To solve the above technical problems, the present invention provides a carbon fiber polyethylene glycol phase change composite material, the components of which and their mass fractions are 100 parts of polyethylene glycol, 20 parts to 100 parts of calcium chloride, 20 to 100 parts of carbon fiber felt, and 0.5 to 3 parts of a coupling agent.

[0008] Furthermore, the polyethylene glycol is polyethylene glycol with a relative molecular weight of 200-2000; and the calcium chloride is chemically pure.

[0009] Furthermore, the carbon fiber felt has a density of 0.1-0.5 g / cm 3 A lightweight carbon / carbon composite material, wherein the carbon fiber content is 90% and the bonding carbon content is 10%. The carbon fiber felt has an xyz three-dimensional network structure. The carbon fiber length is 10-15 cm and is isotropic in the xy plane. The fiber density in the z direction to the fiber in the xy plane is approximately 1:(50-250).

[0010] Furthermore, the coupling agent is silane coupling agent KH550.

[0011] A method for preparing a carbon fiber polyethylene glycol phase change composite material comprises the following steps:

[0012] Step (a) Preparation of complexing solution: polyethylene glycol and calcium chloride are mixed in appropriate proportions, placed in ethanol, and dissolved for later use;

[0013] Step (b) Surface treatment of carbon fiber felt: First, the carbon fiber felt is immersed in a concentrated sulfuric acid solution at 80°C for 2 hours to remove impurities and oxidize the surface. After being taken out and dried, the carbon fiber felt is placed in an ethanol solution containing a silane coupling agent and refluxed at 80°C for 8 hours. The carbon fiber felt is then taken out and dried for later use.

[0014] Step (c) impregnating the carbon fiber felt with the complexing solution: impregnating the treated carbon fiber felt with a solution of polyethylene glycol and calcium chloride, which is adsorbed onto the surface of the carbon fiber felt. In this step, the large specific surface area of the carbon fiber felt allows for the adsorption and grafting of a large amount of the polyethylene glycol and calcium chloride composite system.

[0015] Step (d) Drying and crosslinking the complex system: The impregnated carbon fiber felt was placed in an oven and dried at 80°C for 24 hours, and then cured at 120°C for 2 hours to allow the polyethylene glycol and calcium chloride to crosslink. The purpose of this step is to allow the complex system to be tightly bonded to the surface of the carbon fiber felt;

[0016] Step (e) repeated impregnation and complexation cross-linking: repeatedly repeating steps (c) and (d) to allow a certain amount of phase change material composite system to be complexed on the surface of the carbon fiber felt;

[0017] Step (f) Compression confined molding: The content of the phase change material can be adjusted by adjusting the compression ratio. That is, the above-mentioned complexed and cross-linked carbon fiber polyethylene glycol composite system is placed in a pressing mold, cured at 120°C and 10 MPa for 2 hours, and demolded to finally prepare a carbon fiber polyethylene glycol phase change composite material with a three-dimensional network structure, stable shape, and high thermal conductivity.

[0018] The technical effects of the invention are as follows: (1) Compared with the prior art, the carbon fiber polyethylene glycol phase change composite material of the present invention has the following advantages: (1) polyethylene glycol and calcium chloride can form a complex system, which can solve the problem of melting deformation of the phase change material to a certain extent; (2) the surface treatment of the carbon fiber felt can improve the interface bonding problem between the carbon fiber and the phase change material, and improve the thermal conductivity path; (3) the carbon fiber felt can adsorb the phase change material and has a three-dimensional skeleton structure, which further solves the melting deformation of the phase change material. At the same time, the high thermal conductivity path of the carbon fiber felt can ensure that the composite material has a higher thermal conductivity coefficient; (4) through the method of high-temperature compression and confined pressing, the pores in the composite material system can be reduced, the bonding tightness between the carbon fiber and the polyethylene glycol system can be increased, the thermal conductivity path can be improved, and finally a carbon fiber / polyethylene glycol phase change composite material with a three-dimensional network structure, stable shape and high thermal conductivity coefficient is prepared. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described in detail below with reference to the accompanying drawings:

[0020] Figure 1 Schematic diagram of the metallographic structure of the carbon fiber polyethylene glycol phase change material obtained by surface treatment of the carbon fiber felt in Example 1;

[0021] Figure 2 Schematic diagram of the metallographic structure of the carbon fiber polyethylene glycol phase change material obtained by surface treating the carbon fiber felt in Example 1;

[0022] Figure 3 This is a leakage test diagram of carbon fiber polyethylene glycol phase change material under high temperature conditions. DETAILED DESCRIPTION

[0023] Example 1

[0024] The carbon fiber polyethylene glycol phase change composite material of this embodiment is prepared by the following method:

[0025] Step (a), polyethylene glycol (PEG1500) and calcium chloride are mixed in a mass ratio of 5:1, and then dissolved in ethanol for later use;

[0026] Step (b), carbon fiber felt (0.2 g / cm 3) Soak in concentrated sulfuric acid solution at 80°C for 2 hours to remove impurities and perform surface oxidation treatment. After drying, place in ethanol solution containing silane coupling agent and reflux at 80°C for 8 hours. Then, take out and dry for later use.

[0027] Step (c), immersing the treated carbon fiber felt in a solution of polyethylene glycol and calcium chloride, so that the solution of polyethylene glycol and calcium chloride is adsorbed onto the surface of the carbon fiber felt;

[0028] Step (d) placing the impregnated carbon fiber felt in an oven at 80° C. and drying for 24 hours, and then curing at 120° C. for 2 hours to allow the polyethylene glycol and calcium chloride to form a complex and cross-linked structure;

[0029] Step (e) repeatedly repeating steps (c) and (d) to allow a certain amount of phase change material composite system to be complexed on the surface of the carbon fiber felt;

[0030] Step (f) placing the complex cross-linked carbon fiber / polyethylene glycol composite system into a pressing mold, curing it at 120° C. and 10 MPa for 2 hours with a compression ratio of 3:1, and demolding it to finally prepare a carbon fiber / polyethylene glycol phase change composite material with a three-dimensional network structure, stable shape, and high thermal conductivity.

[0031] The structure of carbon fiber polyethylene glycol phase change material with 3D network structure is as follows Figure 1 (carbon fiber felt after surface treatment) as shown, as a comparison, Figure 2 It is a carbon fiber polyethylene glycol phase change material formed when the carbon fiber felt is not surface treated. Figure 1 It can be seen that the surface-treated carbon fiber and polyethylene glycol are tightly combined to ensure high thermal conductivity, while also firmly locking polyethylene glycol between the fibers to prevent material deformation. Figure 2 It can be seen that when the carbon fiber felt has not passed through the surface, the bonding between the carbon fiber and the polyethylene glycol is loose, and there are a large number of pores, which is not conducive to the formation of a high thermal conductivity path and will seriously reduce the thermal conductivity of the composite material. Figure 3 This is a leakage test diagram of carbon fiber polyethylene glycol phase change material under high temperature conditions. Figure 3 It can be seen that after 15 minutes at 80°C, polyethylene glycol has leaked and deformed, while polyethylene glycol / calcium chloride has slightly leaked but not deformed. After compounding carbon / carbon fiber felt, whether it is a low-content carbon fiber felt (low) or a high-content carbon fiber felt (high), polyethylene glycol / calcium chloride + carbon / carbon fiber felt has no leakage or deformation at all. The final prepared phase change material has a melting point, melting enthalpy, and thermal conductivity of 40°C, 95 J / g, and 3.2W / (mK), and is not prone to leakage and denaturation.

[0032] Example 2

[0033] The carbon fiber polyethylene glycol phase change composite material of this embodiment is prepared by the following method:

[0034] Step (a), polyethylene glycol (PEG2000) and calcium chloride are mixed in a mass ratio of 4:1, and then dissolved in ethanol for later use;

[0035] Step (b), carbon fiber felt (0.2 g / cm 3 ) Soak in concentrated sulfuric acid solution at 80°C for 2 hours to remove impurities and perform surface oxidation treatment. After drying, place in ethanol solution containing silane coupling agent and reflux at 80°C for 8 hours. Then, take out and dry for later use.

[0036] Step (c), immersing the treated carbon fiber felt in a solution of polyethylene glycol and calcium chloride, so that the solution of polyethylene glycol and calcium chloride is adsorbed onto the surface of the carbon fiber felt;

[0037] Step (d), placing the impregnated carbon fiber felt in an oven at 80° C. and drying for 24 hours, and then curing at 120° C. for 2 hours to allow the polyethylene glycol and calcium chloride to form a complex and cross-linked structure;

[0038] Step (e), repeatedly repeating steps (c) and (d) to allow a certain amount of phase change material composite system to be complexed on the surface of the carbon fiber felt;

[0039] In step (f), the complexed and cross-linked carbon fiber / polyethylene glycol composite is placed in a pressing mold and cured at 120°C and 10 MPa for 2 hours with a compression ratio of 2:1. The mold is then released to produce a carbon fiber / polyethylene glycol phase change composite material with a three-dimensional network structure, stable shape, and high thermal conductivity. The resulting phase change material exhibits a melting point, melting enthalpy, and thermal conductivity of 41°C, 80 J / g, and 2.5 W / (mK), and is not susceptible to denaturation.

[0040] Example 3

[0041] The carbon fiber polyethylene glycol phase change composite material of this embodiment is prepared by the following method:

[0042] Step (a), polyethylene glycol (PEG800) and calcium chloride are mixed in a mass ratio of 4:1, and then dissolved in ethanol for later use;

[0043] Step (b), carbon fiber felt (0.2 g / cm 3 ) Soak in concentrated sulfuric acid solution at 80°C for 2 hours to remove impurities and perform surface oxidation treatment. After drying, place in ethanol solution containing silane coupling agent and reflux at 80°C for 8 hours. Then, take out and dry for later use.

[0044] Step (c), immersing the treated carbon fiber felt in a solution of polyethylene glycol and calcium chloride, so that the solution of polyethylene glycol and calcium chloride is adsorbed onto the surface of the carbon fiber felt;

[0045] Step (d), placing the impregnated carbon fiber felt in an oven at 80° C. and drying for 24 hours, and then curing at 120° C. for 2 hours to allow the polyethylene glycol and calcium chloride to form a complex and cross-linked structure;

[0046] Step (e), repeatedly repeating steps (c) and (d) to allow a certain amount of phase change material composite system to be complexed on the surface of the carbon fiber felt;

[0047] In step (f), the complexed and cross-linked carbon fiber / polyethylene glycol composite system is placed in a pressing mold and cured at 120°C and 10 MPa for 2 hours with a compression ratio of 1.5:1. The mold is then released to produce a carbon fiber / polyethylene glycol phase change composite material with a three-dimensional network structure, stable shape, and high thermal conductivity. The resulting phase change material has a melting point, melting enthalpy, and thermal conductivity of 38°C, 78 J / g, and 1.5 W / (m K), and is not susceptible to denaturation.

[0048] Obviously, the above embodiments are merely examples for the purpose of clearly illustrating the present invention and are not intended to limit the manner in which the present invention is to be practiced. Those skilled in the art will readily appreciate that other variations or modifications based on the above description are possible. It is not necessary and impossible to enumerate all possible embodiments here. However, such obvious variations or modifications arising from the spirit of the present invention remain within the scope of protection of the present invention.

Claims

1. A method for preparing a carbon fiber polyethylene glycol phase change composite material, characterized in that: The components of the carbon fiber polyethylene glycol phase change composite material and their mass parts are 100 parts of polyethylene glycol, 20 parts to 100 parts of calcium chloride, 20 parts to 100 parts of carbon fiber felt, and 0.5 parts to 3 parts of silane coupling agent; The polyethylene glycol is polyethylene glycol with a relative molecular weight of 200-2000; the calcium chloride is chemically pure; The carbon fiber felt has a density of 0.1-0.5 g / cm 3 A lightweight carbon / carbon composite material, wherein the carbon fiber content is 90%, the bonding carbon content is 10%, the carbon fiber felt has an xyz three-dimensional network structure, the carbon fiber length is 10-15 cm, isotropic in the xy plane, and the density of the fiber in the z direction to the fiber in the xy plane is 1:(50-250); the silane coupling agent is silane coupling agent KH550; The preparation method comprises the following steps: Step (a) Preparation of complexing solution: polyethylene glycol and calcium chloride are mixed in appropriate proportions, placed in ethanol, and dissolved for later use; Step (b) Surface treatment of carbon fiber felt: First, the carbon fiber felt is immersed in a concentrated sulfuric acid solution at 80°C for 2 hours to remove impurities and oxidize the surface. After being taken out and dried, the carbon fiber felt is placed in an ethanol solution containing a silane coupling agent and refluxed at 80°C for 8 hours. The carbon fiber felt is then taken out and dried for later use. Step (c) impregnating the carbon fiber felt with the complexing solution: impregnating the treated carbon fiber felt with a solution of polyethylene glycol and calcium chloride, which is adsorbed onto the surface of the carbon fiber felt. In this step, the large specific surface area of the carbon fiber felt allows for the adsorption and grafting of a large amount of the polyethylene glycol and calcium chloride composite system. Step (d) Drying and crosslinking the complex system: The impregnated carbon fiber felt was placed in an oven and dried at 80°C for 24 hours, and then cured at 120°C for 2 hours to allow the polyethylene glycol and calcium chloride to crosslink. The purpose of this step is to allow the complex system to be tightly bonded to the surface of the carbon fiber felt; Step (e) repeated impregnation and complexation cross-linking: repeatedly repeating steps (c) and (d) to allow a certain amount of phase change material composite system to be complexed on the surface of the carbon fiber felt; Step (f) Compression Confinement Molding: The content of the phase change material is adjusted by adjusting the compression ratio. That is, the above-mentioned complexed and cross-linked carbon fiber polyethylene glycol composite system is placed in a pressing mold, cured at 120°C and 10 MPa for 2 hours, and demolded to finally prepare a carbon fiber polyethylene glycol phase change composite material with a three-dimensional network structure, stable shape, and high thermal conductivity.

2. The preparation method according to claim 1, characterized in that The polyethylene glycol is PEG1500, and the density of the carbon fiber felt is 0.2 g / cm 3 .

3. The preparation method according to claim 1, characterized in that The mass ratio of the polyethylene glycol to calcium chloride is 5:1.

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