CN113045884B - A carbon fiber polyethylene glycol phase change composite material - Google Patents

Abstract

The invention relates to a carbon fiber polyethylene glycol phase change composite material. The components of the carbon fiber polyethylene glycol phase change composite material are 100 parts by mass of polyethylene glycol and 20-100 parts of chlorinated polyethylene glycol. Calcium, 20-100 parts of carbon fiber felt, 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 phase change materials to a certain extent; surface treatment of carbon fiber felt It can improve the interface bonding problem between carbon fiber and phase change material and improve the thermal conduction path.

Description

A carbon fiber polyethylene glycol phase change composite material

technical field

The invention relates to the technical field of polymer thermally conductive phase-change composite materials, in particular to a carbon fiber polyethylene glycol phase-change composite material with a three-dimensional network structure, stable shape and high thermal conductivity, and a preparation method thereof.

Background technique

The polymer phase change material absorbs heat through melting when the temperature is high, and releases heat through recrystallization when the ambient temperature decreases. During the process of heat absorption or heat release, the temperature of the phase change material remains within a certain range (melting point), This ensures that the temperature of the surrounding environment is stable. The characteristics of polymer phase change materials to stabilize the surrounding temperature within a certain temperature range make them suitable for electronic refrigeration, building heating/cooling (indoor temperature control), floor radiant heating, thermal switches, clothing and other fields.

Commonly used 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 ambient temperature is kept near the melting point of the phase change material by absorbing and releasing heat. However, the thermal conductivity 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). It can be seen from this that the bulk thermal conductivity of the above-mentioned polymer phase change materials is generally low, and in the application of fast energy storage, thermal energy cannot be quickly stored, which limits its application. Therefore, it is necessary to improve the thermal conductivity of polymer phase change materials to meet the needs of fast energy storage.

At this stage, the thermal conductivity of polymer phase change materials is mainly improved by adding high thermal conductivity fillers. Such as by adding metal materials (silver particles, copper particles, silver nanowires, copper nanowires), ceramic materials (boron nitride, aluminum nitride, aluminum oxide), carbon materials (graphite, carbon nanofibers, carbon nanotubes, carbon black, carbon fiber) and other materials to improve the thermal conductivity of polymer phase change materials. The method of obtaining high thermal conductivity of polymer materials is mainly to allow the filler to form a high thermal conductivity path in the polymer matrix, that is, to use various methods to make the filler form a percolation network in the polymer material, so as to make the heat conduction of the polymer phase change material. The coefficient is abruptly changed, so as to obtain a higher thermal conductivity. However, the traditional process method generally achieves percolation by adding a large amount of filler through the blending method, thereby improving the thermal conductivity of the material. However, if the filler is greatly increased, the viscosity of the polymer phase change material will be increased, which will bring difficulties to the processing and molding, and will also reduce the enthalpy (heat storage capacity) and other properties of the polymer material itself. Therefore, the amount of filler added should be as small as possible, so as not to affect the processing performance of the polymer phase change material and the comprehensive physical properties of the material. Through various methods, the filler can form a three-dimensional network structure in the polymer phase change material, thereby forming a high thermal conductivity path, and the heat can rapidly transmit thermal energy on the three-dimensional network structure, so as to achieve a low filler content and a high thermal conductivity. At present, the methods of forming high thermal conductivity paths in polymer composite materials, especially for fiber materials, mainly include freeze-drying orientation method, electroplating molding method, self-assembly molding method, template method and other methods. These methods can improve the thermal conductivity of polymer materials several times or even dozens of times, which is a good method to quickly increase the thermal coefficient, so it has also become a hot spot of recent scientists' research.

Because polymer phase change materials store energy by melting and endothermic methods, after the polymer materials are melted, shrinkage deformation and flow deformation are prone to occur, which brings difficulties to the application of phase change materials. Therefore, in order to reduce the deformation problem of the phase change material, the phase change material needs to be imprisoned. At this stage, the methods for improving the deformation of phase change materials mainly include microcapsule method, adsorption method, crosslinking method and other methods. For example, the phase change material is encapsulated in a polymer shell to form microcapsules, and the polymer shell can prevent the leakage of the phase change material. This method is called the microcapsule method. For example, the method of using a porous material 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. The method of using chemical cross-linking to generate cross-links between the molecular chains of phase-change materials to prevent material deformation is called cross-linking. Therefore, preventing the melt deformation of phase change materials has also become a hot research topic of related scientists in recent years.

SUMMARY OF THE INVENTION

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.

In order to solve the above-mentioned technical problems, the carbon fiber polyethylene glycol phase change composite material provided by the present invention, the component of the material and its mass fraction are 100 parts of polyethylene glycol, 20 to 100 parts of calcium chloride, 20 parts of -100 parts of carbon fiber felt, 0.5-3 parts of coupling agent.

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

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

Further, the coupling agent is a silane coupling agent KH550.

A preparation method of carbon fiber polyethylene glycol phase change composite material, comprising the following steps:

Step (a) preparation of complex solution: after proportioning polyethylene glycol and calcium chloride, put them in ethanol, dissolve, and use for later use;

Step (b) Surface treatment of carbon fiber felt: first, put the carbon fiber felt in a concentrated sulfuric acid solution and soak it at 80°C for 2 hours to remove impurities, carry out oxidation treatment on the surface, take it out and dry it and put it in an ethanol solution containing a silane coupling agent. Reflux at 80°C for 8 hours, take it out and dry it for later use;

Step (c) Carbon fiber felt dipping and complexing solution: the treated carbon fiber felt is dipped into a 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. The large specific surface area can adsorb and graft a large amount of polyethylene glycol and calcium chloride composite system;

Step (d) Drying and complex crosslinking of complex system: put the impregnated carbon fiber felt in an oven to dry at 80°C for 24 hours, and then cure at 120°C for 2 hours to make polyethylene glycol and calcium chloride. Complexation and crosslinking, the purpose of this step is to make the complexation system tightly bond to the surface of the carbon fiber felt;

Step (e) Repeated impregnation and complexation and crosslinking: Repeat steps (c) and (d) repeatedly, so that a certain amount of phase change material composite system is complexed on the surface of the carbon fiber felt;

Step (f) Compression Confinement Forming: The content of the phase change material can be adjusted by adjusting the compression ratio, that is, the above-mentioned complex and cross-linked carbon fiber polyethylene glycol composite system is put into a pressing mold and cured under the action of 120 ° C and 10 MPa 2 hours, demoulding, and finally prepared a carbon fiber polyethylene glycol phase change composite material with a three-dimensional network structure, stable shape and high thermal conductivity.

Technical effects of the invention: (1) 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 phase change to a certain extent. The problem of material melt deformation; (2) the surface treatment of carbon fiber felt can improve the interface bonding between carbon fiber and phase change material, and improve the thermal conduction path; (3) carbon fiber felt can adsorb phase change material, and has a three-dimensional skeleton structure, which can further solve the problem of phase change. At the same time, the high thermal conductivity of the carbon fiber felt can ensure that the composite material has a high thermal conductivity; (4) through the method of high temperature compression confinement pressing, the pores in the composite material system can be reduced, and the carbon fiber and polyethylene The degree of bonding of the alcohol system improves the thermal conductivity, and finally a carbon fiber/polyethylene glycol phase change composite material with a three-dimensional network structure, stable shape and high thermal conductivity is prepared.

Description of drawings

The present invention is described in further detail below in conjunction with the accompanying drawings of the description:

Fig. 1 is the metallographic schematic diagram of carbon fiber polyethylene glycol phase change material obtained by surface treatment of carbon fiber felt in Example 1;

Fig. 2 is the metallographic schematic diagram of carbon fiber polyethylene glycol phase change material obtained by carbon fiber felt without surface treatment in Example 1;

Figure 3 is a leak test chart of carbon fiber polyethylene glycol phase change material under high temperature conditions.

Detailed ways

Example 1

The carbon fiber polyethylene glycol phase change composite material of the present embodiment is prepared by the following method:

In step (a), after the polyethylene glycol (PEG1500) and calcium chloride are proportioned in a mass ratio of 5:1, they are put into ethanol, dissolved, and used for later use;

In step (b), the carbon fiber felt (0.2 g/cm ³ ) was soaked in concentrated sulfuric acid solution at 80° C. for 2 hours to remove impurities, the surface was oxidized, taken out and dried and placed in an ethanol solution containing a silane coupling agent , refluxed at 80°C for 8 hours, taken out to dry, and used for later use;

In step (c), the treated carbon fiber felt is dipped into a 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;

Step (d) put the impregnated carbon fiber felt in an oven to dry at 80° C. for 24 hours, and then cure at 120° C. for 2 hours, so that polyethylene glycol and calcium chloride are complexed and cross-linked;

Step (e) repeating steps (c) and (d) repeatedly, so that a certain amount of phase change material composite system is complexed on the surface of the carbon fiber felt;

Step (f) Put the above-mentioned complexed and cross-linked carbon fiber/polyethylene glycol composite system into a pressing mold, cure at 120° C. and 10 MPa for 2 hours, wherein the compression ratio is 3:1, demould, and finally prepare A carbon fiber/polyethylene glycol phase change composite material with three-dimensional network structure, stable shape and high thermal conductivity is obtained.

The structure of the carbon fiber polyethylene glycol phase change material with 3D network structure is shown in Figure 1 (the carbon fiber felt is surface-treated). For comparison, Figure 2 is the carbon fiber polyethylene glycol phase formed when the carbon fiber felt is not surface-treated. variable material. It can be seen from Figure 1 that the surface-treated carbon fiber fibers and polyethylene glycol are closely combined, which can ensure high thermal conductivity, and at the same time, the polyethylene glycol can be firmly confined between the fibers to prevent material deformation. As can be seen from Figure 2, when the carbon fiber felt does not pass through the surface, the bonding between carbon fiber and polyethylene glycol is loose, and there are a large number of pores, which is not conducive to the formation of high thermal conductivity paths, and will seriously reduce the thermal conductivity of the composite material. Figure 3 is a leak test chart of carbon fiber polyethylene glycol phase change material under high temperature conditions. It can be seen from Figure 3 that after 15 minutes at a temperature of 80 °C, polyethylene glycol has leaked and deformed, while polyethylene glycol/calcium chloride leaks slightly, but there is no deformation. After /carbon fiber felt, whether it is low content carbon fiber felt (low) or high content carbon fiber felt (high), polyethylene glycol/calcium chloride + carbon/carbon fiber felt has no leakage and deformation at all. The melting point, melting enthalpy and thermal conductivity of the final prepared phase change material can reach 40 °C, 95 J/g, 3.2 W/(m K), and leakage denaturation is not easy to occur.

Example 2

The carbon fiber polyethylene glycol phase change composite material of the present embodiment is prepared by the following method:

In step (a), after the polyethylene glycol (PEG2000) and calcium chloride are proportioned in a mass ratio of 4:1, they are put into ethanol, dissolved, and used for later use;

In step (b), the carbon fiber felt (0.2 g/cm ³ ) was soaked in concentrated sulfuric acid solution at 80° C. for 2 hours to remove impurities, the surface was oxidized, taken out and dried and placed in an ethanol solution containing a silane coupling agent , refluxed at 80°C for 8 hours, taken out to dry, and used for later use;

In step (c), the treated carbon fiber felt is dipped into a 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;

Step (d), put the impregnated carbon fiber felt in an oven to dry at 80°C for 24 hours, and then cure at 120°C for 2 hours, so that polyethylene glycol and calcium chloride are complexed and cross-linked;

Step (e), repeating steps (c) and (d) repeatedly, so that a certain amount of phase change material composite system is complexed on the surface of the carbon fiber felt;

Step (f), put the above-mentioned complex and cross-linked carbon fiber/polyethylene glycol composite system into a pressing mold, and cure at 120 ° C under the action of 10 MPa for 2 hours, wherein the compression ratio is 2:1, demoulding, and finally A carbon fiber/polyethylene glycol phase change composite material with three-dimensional network structure, stable shape and high thermal conductivity is prepared. The melting point, melting enthalpy, and thermal conductivity of the final prepared phase change material can reach 41 °C, 80 J/g, 2.5 W/(m K), and are not prone to denaturation.

Example 3

The carbon fiber polyethylene glycol phase change composite material of the present embodiment is prepared by the following method:

In step (a), after the polyethylene glycol (PEG800) and calcium chloride are proportioned in a mass ratio of 4:1, they are put into ethanol, dissolved, and used for later use;

In step (b), the carbon fiber felt (0.2 g/cm ³ ) was soaked in concentrated sulfuric acid solution at 80° C. for 2 hours to remove impurities, the surface was oxidized, taken out and dried and placed in an ethanol solution containing a silane coupling agent , refluxed at 80°C for 8 hours, taken out to dry, and used for later use;

In step (c), the treated carbon fiber felt is dipped into a 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;

Step (d), put the impregnated carbon fiber felt in an oven to dry at 80°C for 24 hours, and then cure at 120°C for 2 hours, so that polyethylene glycol and calcium chloride are complexed and cross-linked;

Step (e), repeating steps (c) and (d) repeatedly, so that a certain amount of phase change material composite system is complexed on the surface of the carbon fiber felt;

Step (f), put the above-mentioned complex and cross-linked carbon fiber/polyethylene glycol composite system into a pressing mold, and cure at 120 ° C under the action of 10 MPa for 2 hours, wherein the compression ratio is 1.5: 1, demoulding, and finally A carbon fiber/polyethylene glycol phase change composite material with three-dimensional network structure, stable shape and high thermal conductivity is prepared. The melting point, melting enthalpy, and thermal conductivity of the final prepared phase change material can reach 38 °C, 78 J/g, 1.5 W/(m K), and are not prone to denaturation.

Obviously, the above-mentioned embodiments are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those of ordinary skill in the art, changes or modifications in other different forms can also be made on the basis of the above description. There is no need and cannot be exhaustive of all implementations here. However, these obvious changes or changes derived from the spirit of the present invention are still within the protection scope of the present invention.

Claims (4)

1. The carbon fiber polyethylene glycol phase change composite material is characterized by comprising the following components, by mass, 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 preparation method of the carbon fiber polyethylene glycol phase change composite material comprises the following steps,

preparing a complexing solution in the step (a): after polyethylene glycol and calcium chloride are proportioned, the mixture is put into ethanol for dissolving for standby;

step (b) surface treatment of the carbon fiber felt: firstly, putting a carbon fiber felt into a concentrated sulfuric acid solution, soaking for 2 hours at 80 ℃, removing impurities, carrying out oxidation treatment on the surface, taking out and drying, putting the carbon fiber felt into an ethanol solution containing a silane coupling agent, carrying out reflux treatment for 8 hours at 80 ℃, taking out and drying for later use;

step (c), soaking the carbon fiber felt in a complexing solution: dipping the treated carbon fiber felt into a solution of polyethylene glycol and calcium chloride, and adsorbing the solution of polyethylene glycol and calcium chloride on the surface of the carbon fiber felt, wherein a large amount of polyethylene glycol and calcium chloride composite systems can be adsorbed and grafted through the large specific surface area of the carbon fiber felt;

step (d) drying and complex crosslinking of the complex system: putting the impregnated carbon fiber felt into an oven, drying the carbon fiber felt for 24 hours at the temperature of 80 ℃, and then curing the carbon fiber felt for 2 hours at the temperature of 120 ℃ to complex and crosslink polyethylene glycol and calcium chloride, wherein the aim of the step is to enable a complex system to be tightly combined on the surface of the carbon fiber felt;

step (e) repeated impregnation and complex crosslinking: repeating the steps (c) and (d) repeatedly to complex a certain amount of phase-change material composite system on the surface of the carbon fiber felt;

step (f), compression and limited area molding: the content of the phase-change material can be adjusted by adjusting the compression multiple, namely, the carbon fiber polyethylene glycol composite system subjected to complexing and crosslinking is placed into a pressing die, is cured for 2 hours at the temperature of 120 ℃ under the action of 10MPa, and is demoulded, so that the carbon fiber polyethylene glycol phase-change composite material with a three-dimensional network structure, a stable shape and a high heat conductivity coefficient is finally prepared.

2. The carbon fiber polyethylene glycol phase change composite material as claimed in claim 1, wherein the polyethylene glycol is polyethylene glycol having a relative molecular weight of 200-2000; the calcium chloride is chemically pure.

3. The carbon fiber polyethylene glycol phase change composite material as claimed in claim 2, wherein the carbon fiber felt has a density of 0.1-0.5 g/cm ³ The light carbon/carbon composite material comprises 90% of carbon fibers, 10% of bonding carbon, an x-y-z three-dimensional net structure of the carbon fiber felt, 10-15 cm of the carbon fibers, isotropy in an x-y plane, and 1: (50-250).

4. The carbon fiber polyethylene glycol phase change composite material according to claim 3, wherein the silane coupling agent is silane coupling agent KH550.

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