Carbon fiber polyethylene glycol phase change composite material with 3D thermal conductive skeleton structure

Abstract

The present invention relates to a carbon fiber polyethylene glycol phase change composite material with a 3D heat-conducting skeleton structure. The components and their mass fractions of the carbon fiber polyethylene glycol phase change composite material are 100 parts of polyethylene glycol, 20 parts - 100 parts of calcium chloride, 20 - 100 parts of carbon fiber felt, and 0.5 - 3 parts of coupling agent; 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 interfacial bonding problem between the carbon fiber and the phase change material and improve the heat conduction path.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer thermal conductive phase change composite materials, in particular to a carbon fiber polyethylene glycol phase change composite material with a 3D thermal conductive skeleton structure. Background Art

[0002] Polymer phase change materials absorb heat through melting at high temperatures and release heat through recrystallization when the surrounding temperature decreases. During the process of absorbing or releasing heat, the temperature of the phase change material remains within a certain range (melting point), thereby ensuring the stability of the surrounding environment temperature. The characteristic of polymer phase change materials to keep the surrounding temperature stable within a certain temperature range enables their application in fields such as electronic refrigeration, building heating / cooling (indoor temperature control), floor radiant heating, thermal switches, and clothing.

[0003] Common polymer phase change materials and their melting points are Eicosane (36 °C), Octadecane (28 °C), 1-dodecanol (22 °C), RT-22 (25.37 °C), Octadecanol (28.91 °C), RT27 (28.81 °C). These polymer phase change materials can ensure that the environmental temperature remains near the melting point of the phase change material by absorbing and releasing heat. However, the thermal conductivity coefficients of the above polymer phase change materials are 0.13 W / (m•K) (RT27), 0.17 W / (m•K) (Octadecane), 0.26 W / (m•K) (RT25), 0.36 W / (m•K) (Eicosane), 0.42 W / (m•K) (Tetradecanol), 0.48 W / (m•K) (Capric acid) respectively. It can be seen that the bulk thermal conductivity coefficients of the above polymer phase change materials are generally low, and during rapid energy storage applications, heat energy cannot be stored quickly, restricting their application. Therefore, it is necessary to increase the thermal conductivity coefficient of polymer phase change materials to meet the requirements of rapid energy storage.

[0004] At present, the main method to improve the thermal conductivity of polymer phase change materials is to add high thermal conductivity fillers. For example, the thermal conductivity of polymer phase change materials can be improved by adding metal materials (silver particles, copper particles, silver nanowires, copper nanowires), ceramic materials (boron nitride, aluminum nitride, alumina), carbon materials (graphite, carbon nanofibers, carbon nanotubes, carbon black, carbon fibers), etc. The main method for polymer materials to obtain high thermal conductivity is to form high thermal conductivity pathways in the polymer matrix, that is, various methods are used to form a percolation network of fillers in the polymer materials, so that the thermal conductivity of the polymer phase change materials undergoes a sudden change, thereby obtaining a relatively high thermal conductivity. However, the traditional process method generally achieves percolation by adding a large amount of fillers through the blending method, thereby improving the thermal conductivity of the materials. However, if the amount of added fillers is increased significantly, it will increase the viscosity of the polymer phase change materials, bringing difficulties to processing and molding. At the same time, it will also reduce the enthalpy (heat storage capacity) and other properties of the polymer materials themselves. Therefore, the amount of filler added should be as small as possible to avoid affecting the processing performance and comprehensive physical properties of the polymer phase change materials. Through various methods, the fillers can form a three-dimensional network structure in the polymer phase change materials, thereby forming a high thermal conductivity pathway, and heat can be quickly transmitted on the three-dimensional network structure, so as to achieve the situation of high thermal conductivity with a low filler content. At present, the methods to form high thermal conductivity pathways in polymer composites, especially for fiber materials, mainly include freeze-drying orientation method, electroplating forming method, self-assembly forming method, template method, etc. These methods can increase the thermal conductivity of polymer materials by several times or even dozens of times, which is a good method to quickly increase the thermal coefficient, so it has also become a research hotspot for scientists in recent years.

[0005] Since polymer phase change materials store energy by melting and absorbing heat, after the polymer materials melt, they are prone to shrinkage deformation and flow deformation, which brings difficulties to the application of phase change materials. Therefore, in order to reduce the deformation problem of the phase change materials, it is necessary to confine the phase change materials. At present, the main methods to improve the deformation of phase change materials mainly include microencapsulation method, adsorption method, crosslinking method, etc. For example, encapsulating the phase change material in a polymer shell to form microcapsules, and the polymer shell can prevent the leakage of the phase change material, and this method is called the microencapsulation method. For example, using porous materials with a relatively large specific surface area to adsorb the phase change material, thereby preventing the flow of the phase change material is called the adsorption method. Using chemical crosslinking methods to generate crosslinks between the molecular chains of the phase change material, thereby preventing the deformation of the material is called the crosslinking method. Therefore, preventing the melting deformation of phase change materials has also become a research hotspot for 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 melting deformation and having a 3D thermal conductive skeleton structure and its preparation method.

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

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

[0009] Further, the carbon fiber felt is a lightweight carbon / carbon composite material with a density of 0.1 - 0.5 g / cm 3 , in which the content of carbon fiber is 90%, the content of binder carbon is 10%. The carbon fiber felt has an x - y - z three - dimensional network structure. The length of the carbon fiber is 10 - 15 cm, is isotropic in the x - y plane, and the fiber density in the z - direction and the fiber density in the x - y plane is about 1:(50 - 250).

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

[0011] A preparation method of the carbon fiber polyethylene glycol phase change composite material includes the following steps.

[0012] Step (a) Preparation of complexing solution: After proportioning polyethylene glycol and calcium chloride, put them into ethanol for dissolution and reserve.

[0013] Step (b) Surface treatment of carbon fiber felt: First, put the carbon fiber felt into concentrated sulfuric acid solution and soak it at 80°C for 2 hours to remove impurities and perform surface oxidation treatment. After taking it out and drying, put it into an ethanol solution containing silane coupling agent and reflux it at 80°C for 8 hours. Then take it out and dry for reserve.

[0014] Step (c) Impregnation of carbon fiber felt with complexing solution: Immerse the treated carbon fiber felt into the solution of polyethylene glycol and calcium chloride. The solution of polyethylene glycol and calcium chloride is adsorbed on the surface of the carbon fiber felt. In this step, due to the large specific surface area of the carbon fiber felt, a large amount of polyethylene glycol and calcium chloride composite system can be adsorbed and grafted.

[0015] Step (d) Drying and complexing cross - linking of complexing system: Put the impregnated carbon fiber felt into an oven and dry it at 80°C for 24 hours, and then cure it at 120°C for 2 hours to make polyethylene glycol and calcium chloride complex and cross - link. The purpose of this step is to make the complexing system tightly combine with the surface of the carbon fiber felt.

[0016] Step (e) Repeated impregnation and complexing cross - linking: Repeatedly repeat steps (c) and (d) to make a certain amount of phase change material composite system complexed on the surface of the carbon fiber felt.

[0017] Step (f) Compression and confinement forming: By adjusting the compression ratio, the content of the phase change material can be adjusted. That is, the above complex cross-linked carbon fiber-polyethylene glycol composite system is placed in a pressing mold and cured at 120 °C under a pressure of 10 MPa for 2 hours, and then demolded. Finally, a carbon fiber-polyethylene glycol phase change composite material with a three-dimensional network structure, shape stability, and high thermal conductivity is prepared.

[0018] Technical effects of the invention: (1) For the carbon fiber-polyethylene glycol phase change composite material of the present invention, compared with the prior art, (1) polyethylene glycol and calcium chloride can form a complex system, which can solve the problem of molten deformation of the phase change material to a certain extent; (2) The surface treatment of the carbon fiber felt can improve the interfacial bonding problem between the carbon fiber and the phase change material and improve the heat conduction path; (3) The carbon fiber felt can adsorb the phase change material and has a three-dimensional skeleton structure, further solving the molten deformation of the phase change material. At the same time, the high heat conduction path of the carbon fiber felt can ensure that the composite material has a high thermal conductivity; (4) By the method of high-temperature compression and confinement 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, and the heat conduction path can be improved. Finally, a carbon fiber / polyethylene glycol phase change composite material with a three-dimensional network structure, shape stability, and high thermal conductivity is prepared. Description of the drawings

[0019] The present invention will be further described in detail below in conjunction with the drawings of the specification:

[0020] Figure 1 is the metallographic diagram of the carbon fiber-polyethylene glycol phase change material prepared by surface treatment of the carbon fiber felt in Example 1;

[0021] Figure 2 is the metallographic diagram of the carbon fiber-polyethylene glycol phase change material prepared without surface treatment of the carbon fiber felt in Example 1;

[0022] Figure 3 is the leakage test diagram of the carbon fiber-polyethylene glycol phase change material under high temperature conditions. Specific embodiments

[0023] Example 1

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

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

[0026] In step (b), the carbon fiber felt (0.2 g / cm 3)(Put it) into concentrated sulfuric acid solution and soak at 80 °C for 2 hours to remove impurities. Conduct surface oxidation treatment, take it out and dry it, then put it into an ethanol solution containing silane coupling agent and reflux at 80 °C for 8 hours, take it out and dry it for standby;

[0027] Step (c): Immerse the treated carbon fiber felt into a solution of polyethylene glycol and calcium chloride, and the solution of polyethylene glycol and calcium chloride is adsorbed onto the surface of the carbon fiber felt;

[0028] Step (d): Put the impregnated carbon fiber felt into an oven and dry it at 80 °C for 24 hours, then cure it at 120 °C for 2 hours to make polyethylene glycol and calcium chloride complex and crosslink;

[0029] Step (e): Repeat steps (c) and (d) repeatedly to make a certain amount of phase change material composite system complex on the surface of the carbon fiber felt;

[0030] Step (f): Put the above complex crosslinked carbon fiber / polyethylene glycol composite system into a pressing mold and cure it at 120 °C under the action of 10 MPa for 2 hours, where the compression ratio is 3:1, demold, and finally prepare a carbon fiber / polyethylene glycol phase change composite material with a three-dimensional network structure, shape stability, and high thermal conductivity.

[0031] The structure of the carbon fiber polyethylene glycol phase change material with a 3D network structure is as Figure 1 (The carbon fiber felt has been surface-treated) shown. By contrast, Figure 2 is the carbon fiber polyethylene glycol phase change material formed when the carbon fiber felt is not surface-treated. From Figure 1 it can be seen that after surface treatment, the carbon fiber and polyethylene glycol are tightly combined, which can ensure high thermal conductivity. At the same time, polyethylene glycol can be firmly confined between the fibers to prevent material deformation. And from Figure 2 it can be seen that when the carbon fiber felt is not surface-treated, the combination between the carbon fiber and polyethylene glycol is loose, 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 is the leakage test diagram of the carbon fiber polyethylene glycol phase change material under high temperature conditions. From 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 with carbon / carbon fiber felt, whether it is a low-content carbon fiber felt (low) or a high-content carbon fiber felt (high), there is no phenomenon of leakage and deformation of polyethylene glycol / calcium chloride + carbon / carbon fiber felt. The melting point, melting heat enthalpy, and thermal conductivity of the finally prepared phase change material can reach 40 °C, 95 J / g, 3.2 W / (m K), and it is not easy to leak and denature.

[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): After mixing polyethylene glycol (PEG2000) and calcium chloride at a mass ratio of 4:1, put them into ethanol for dissolution and set aside;

[0035] Step (b): Put the carbon fiber felt (0.2 g / cm 3 ) into concentrated sulfuric acid solution and soak it at 80 °C for 2 hours to remove impurities, perform surface oxidation treatment, take it out and dry it, then put it into an ethanol solution containing silane coupling agent, reflux it at 80 °C for 8 hours, take it out and dry it for later use;

[0036] Step (c): Immerse the treated carbon fiber felt into the solution of polyethylene glycol and calcium chloride, and the solution of polyethylene glycol and calcium chloride is adsorbed on the surface of the carbon fiber felt;

[0037] Step (d): Put the impregnated carbon fiber felt into an oven and dry it at 80 °C for 24 hours, then cure it at 120 °C for 2 hours to make polyethylene glycol and calcium chloride complex and crosslink;

[0038] Step (e): Repeatedly repeat steps (c) and (d) to make a certain amount of phase change material composite system complex on the surface of the carbon fiber felt;

[0039] Step (f): Put the above complex crosslinked carbon fiber / polyethylene glycol composite system into a pressing mold, cure it at 120 °C under the action of 10 MPa for 2 hours, where the compression ratio is 2:1, demold, and finally prepare a carbon fiber / polyethylene glycol phase change composite material with a three-dimensional network structure, stable shape and high thermal conductivity. The melting point, melting enthalpy and thermal conductivity of the finally prepared phase change material can reach 41 °C, 80 J / g, 2.5 W / (m·K), and it is not easy to denature.

[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): After mixing polyethylene glycol (PEG800) and calcium chloride at a mass ratio of 4:1, put them into ethanol for dissolution and set aside;

[0043] Step (b): Put the carbon fiber felt (0.2 g / cm 3 ) into concentrated sulfuric acid solution and soak it at 80 °C for 2 hours to remove impurities, perform surface oxidation treatment, take it out and dry it, then put it into an ethanol solution containing silane coupling agent, reflux it at 80 °C for 8 hours, take it out and dry it for later use;

[0044] Step (c): Immerse the treated carbon fiber felt into a solution of polyethylene glycol and calcium chloride, and the solution of polyethylene glycol and calcium chloride is adsorbed onto the surface of the carbon fiber felt.

[0045] Step (d): Place the impregnated carbon fiber felt in an oven and dry it for 24 hours at 80 °C, and then cure it for 2 hours at 120 °C to allow the polyethylene glycol and calcium chloride to complex and crosslink.

[0046] Step (e): Repeat steps (c) and (d) repeatedly to allow a certain amount of the phase change material composite system to complex on the surface of the carbon fiber felt.

[0047] Step (f): Place the above complexed and crosslinked carbon fiber / polyethylene glycol composite system into a pressing mold, cure it for 2 hours under the action of 120 °C and 10 MPa, where the compression ratio is 1.5:1, and demold to finally prepare a carbon fiber / polyethylene glycol phase change composite material with a three-dimensional network structure, shape stability, and high thermal conductivity. The melting point, melting enthalpy, and thermal conductivity of the finally prepared phase change material can reach 38 °C, 78 J / g, and 1.5 W / (m K), respectively, and it is not prone to denaturation.

[0048] Obviously, the above embodiments are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And these obvious changes or variations derived from the spirit of the present invention are still within the protection scope of the present invention.

Claims

1. A carbon fiber polyethylene glycol phase change composite material, characterized in that Its components and their mass fractions are 100 parts of polyethylene glycol, 20 - 100 parts of calcium chloride, 20 - 100 parts of carbon fiber felt, and 0.5 - 3 parts of silane coupling agent; The carbon fiber felt is a lightweight carbon / carbon composite material with a density of 0.1-0.5 g / cm 3 . Among them, the content of carbon fiber is 90%, and the content of bonded carbon is 10%. The carbon fiber felt has an x-y-z three-dimensional network structure. The length of the carbon fiber is 10-15 cm, is isotropic in the x-y plane, and the fiber density in the z direction and the fiber density in the x-y plane is 1:(50-250); The preparation method of the carbon fiber polyethylene glycol phase change composite material includes the following steps: Step (a) Preparation of complexing solution: After proportioning polyethylene glycol and calcium chloride, put them into ethanol for dissolution and reserve; Step (b) Surface treatment of carbon fiber felt: First, put the carbon fiber felt into concentrated sulfuric acid solution and soak it at 80 °C for 2 hours to remove impurities and perform surface oxidation treatment. After taking it out and drying, put it into an ethanol solution containing silane coupling agent and reflux it at 80 °C for 8 hours. Then take it out and dry for reserve; Step (c) Impregnation of carbon fiber felt with complexing solution: Immerse the treated carbon fiber felt into the solution of polyethylene glycol and calcium chloride. The solution of polyethylene glycol and calcium chloride is adsorbed on the surface of the carbon fiber felt. In this step, due to the large specific surface area of the carbon fiber felt, a large amount of polyethylene glycol and calcium chloride composite system can be adsorbed and grafted; Step (d) Drying and complexing cross - linking of complexing system: Put the impregnated carbon fiber felt into an oven and dry it at 80 °C for 24 hours, and then cure it at 120 °C for 2 hours to make polyethylene glycol and calcium chloride complex and cross - link. The purpose of this step is to tightly combine the complexing system to the surface of the carbon fiber felt; Step (e) Repeated impregnation and complexing cross - linking: Repeatedly repeat steps (c) and (d) to make a certain amount of phase change material composite system complexed on the surface of the carbon fiber felt; Step (f) Compression and confinement molding: By adjusting the compression ratio, the content of the phase change material can be adjusted. That is, put the above - mentioned complexed and cross - linked carbon fiber polyethylene glycol composite system into a pressing mold and cure it at 120 °C under the action of 10 MPa for 2 hours, then demold to finally prepare a carbon fiber polyethylene glycol phase change composite material with a three - dimensional network structure, stable shape, and high thermal conductivity.

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