CN116496591A - High-molecular shaping phase-change material with uniformly distributed heat conducting filler and preparation process thereof - Google Patents

Abstract

The invention discloses a macromolecule shaping phase change material with evenly distributed heat conducting filler and a preparation process thereof, which relate to the field of macromolecule materials. According to the invention, a section of constant-temperature polymerization reaction is introduced before the high-heat-conductivity filler is mixed, so that the viscosity of a solution system is improved, the gravity sedimentation and agglomeration of the heat-conductivity filler are inhibited, the heat-conductivity filler is uniformly dispersed in the system, and the formation of a heat-conductivity passage is facilitated; the high heat conduction filler is introduced into the solution system, fully stirred and vacuumized, and bubbles in the solution are discharged, so that the heat transfer resistance caused by gas is eliminated, and the comprehensive heat conduction performance of the material is enhanced.

Description

A polymer shaped phase change material with uniform distribution of thermally conductive fillers and its preparation process

technical field

The invention relates to the field of polymer materials, in particular to a polymer shaped phase-change material with evenly distributed heat-conducting fillers and a preparation process thereof.

Background technique

In recent years, phase change latent heat energy storage technology has been widely used in various fields due to its large heat storage capacity and isothermal phase change characteristics, including building energy saving, automotive engine thermal management, battery thermal management, solar thermal utilization, etc. Phase change materials include organic, inorganic, and mixed phase change materials. Among them, organic phase change materials have attracted extensive attention for their advantages of no supercooling, no phase separation, stable chemical properties, and low corrosion, including paraffin, fatty acid, and polyols. , fatty acid methyl ester, polyethylene glycol, etc. However, when the phase change material is directly mixed with other structures or materials in the application scenario, it is still easy to leak when it is melted, resulting in a decrease in thermal and chemical stability, while thermal energy storage devices have high cost, large volume, and container corrosion. question. In order to prevent the liquid leakage of organic phase change materials during the energy storage process of phase transition, the stereotyped composite phase change materials composed of phase change materials and polymer substrates have become the mainstream application materials. Since the polymer substrate is resistant to temperatures higher than the melting point of the solid-liquid phase change material, even if the phase change material melts, the composite material can maintain a macroscopic solid state and have good encapsulation properties. Nevertheless, the thermal conductivity of this composite shaped phase change material is poor, and the thermal conductivity is only 0.2-0.3W/m/K, and the heat transfer enhancement of the material has attracted much attention.

The traditional optimization of heat transfer performance is mainly carried out by adding high thermal conductivity fillers, including carbon nanotubes, expanded graphite, graphene, metal and metal oxide powders, etc. Among them, carbon materials are characterized by their excellent thermal properties, electrical properties, and chemical stability. , and the larger specific surface area and density relative to metals, it has become a widely used thermal and conductive filler. However, the current method of adding high thermal conductivity fillers such as carbon nanotubes to phase change materials is generally carried out by stirring, which has caused two major problems. On the one hand, the composite material needs to pass through the process of standing and cooling before it can be formed and removed. However, the material itself has a thickness, and the carbon material in it sinks under the action of gravity, and the continuous irregular movement of the carbon material will cause agglomeration and lead to synthesis. The stereotyped phase change material produces delamination and uneven distribution; on the other hand, the existing preparation method ignores the bubble removal problem, and the high thermal conductivity filler introduces a large number of bubbles into the interior during the high-speed stirring process, and the small pores left in the material are reduced. The thermal conductivity of the material.

Therefore, those skilled in the art are devoting themselves to developing a polymer shaped phase change material with uniform distribution of thermal conductive fillers and its preparation process. The preparation process produces uniform fillers inside the material, which can effectively reduce the gas content in the material.

Contents of the invention

In view of the above-mentioned defects in the prior art, the technical problem to be solved by the present invention is that the polymer shaped phase change material needs to pass through the process of standing and cooling before it can be molded and removed. Due to the thickness of the material itself, the high thermal conductivity filler in it is easily affected. Subsidence due to gravity, and the continuous irregular molecular movement of high thermal conductivity fillers will cause agglomeration, resulting in stratification and uneven distribution of thermal conductivity fillers in shaped phase change materials. The existing preparation method of blending high thermal conductivity fillers ignores the problem of defoaming. The high thermal conductivity fillers introduce a large number of bubbles into the interior during the high-speed stirring process, and the small pores left in the material will significantly affect the overall thermal conductivity of the material.

In order to achieve the above object, the present invention provides a polymer shaped phase change material with evenly distributed thermal conductive filler and its preparation process

The invention discloses a process for preparing a polymer shaped phase change material with uniform distribution of thermally conductive fillers, the preparation of which comprises the following steps:

(1) Take a certain amount of macromolecular monomer and initiator, add in the there-necked flask, mix and stir at a certain temperature and carry out prepolymerization;

(2) adding the organic phase change material into the flask and mixing and stirring until fully dissolved;

(3) Continue constant temperature polymerization at a certain temperature until the system reaches a certain viscosity;

(4) Add the thermally conductive filler into the flask, mix and stir under the above conditions until fully mixed;

(5) Pour the mixed solution in the three-necked flask into the mould, and keep it for a period of time with a certain degree of vacuum in a vacuum oven to fully remove the air bubbles;

(6) Place the mold containing the mixed solution in step (5) in a vacuum drying oven to subject the sample to a high-temperature curing reaction, and then demoulding after cooling at room temperature to obtain a polymer shaped phase change material with uniform distribution of thermally conductive fillers.

Preferably, the polymer monomer in step (1) is selected from MMA.

Preferably, the initiator in step (1) is selected from AIBN.

Preferably, the prepolymerization reaction temperature in step (1) is 70-80°C.

Preferably, the prepolymerization reaction time in step (1) is 30 minutes.

Preferably, the organic phase change material in step (2) is selected from polyethylene glycol (PEG), paraffin wax (PA), fatty acid.

Further, step (3) of the present invention is a process of constant temperature polymerization reaction for a period of time before adding the thermally conductive filler. The specific time length is adjusted in combination with the material properties of the specific application. The longer the step is carried out, the greater the in-situ polymerization reaction. The higher the conversion rate, the higher the viscosity of the solution, which can inhibit the agglomeration behavior of the carbon material under the random motion and the sinking behavior under the action of gravity after the step (5) after the stirring is completed, so as to realize the uniform dispersion of the carbon material in the whole system among. If the viscosity in step (3) is too high, it will lead to insufficient defoaming in step (5). Therefore, it is necessary to determine a reasonable viscosity in step (3) to ensure the uniform distribution of carbon materials and ensure the smooth completion of defoaming.

Preferably, the certain viscosity described in step (3) has a viscosity range of 65-190mPa·s.

Preferably, the thermally conductive filler in step (4) is selected from CNT, carbon nanofibers, carbon fibers, graphene, and expanded graphite.

Preferably, the temperature of the high-temperature curing reaction in step (6) is 80° C., and the reaction time is 4 hours.

The present invention also provides a polymer shaped phase-change material with evenly distributed heat-conducting fillers, which is characterized in that it is prepared by the above-mentioned preparation process.

technical effect

(1) The present invention introduces a high thermal conductivity filler blending process on the basis of the in-situ polymerization process of the three major links of pre-polymerization, constant temperature polymerization, and high-temperature curing of polymer shaped phase change materials. The main feature is that by controlling the time of constant temperature polymerization, the regulation The viscosity of the solution system, when the viscosity rises to a certain value, introduce high thermal conductivity fillers for mixing.

By adjusting the viscosity of the system during the in-situ polymerization of the polymer monomer, the mixed high thermal conductivity filler is subjected to the viscous resistance of the system, and its microscopic movement is suppressed, thereby avoiding the sedimentation under the action of gravity and the agglomeration between the fillers.

By introducing a constant temperature polymerization reaction before mixing the high thermal conductivity filler, the viscosity of the solution system is increased, the gravity sedimentation and agglomeration behavior of the thermal conductivity filler are suppressed, and the thermal conductivity filler is evenly dispersed in the system, which is conducive to the formation of the thermal conduction path and strengthens the synthesis of materials. thermal conductivity.

(2) Vacuum defoaming treatment is carried out after the high thermal conductivity filler blending process, and finally it is cooled and shaped after high temperature curing. The gas introduced in the high thermal conductivity filler blending stage can be drawn out of the system under the action of negative pressure by vacuuming, effectively reducing the gas content in the composite material.

The high thermal conductivity filler is introduced into the solution system and then fully stirred, then vacuumized to discharge the bubbles inside the solution, which is beneficial to eliminate the heat transfer resistance caused by the gas and strengthen the comprehensive thermal conductivity of the material.

The idea, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings, so as to fully understand the purpose, features and effects of the present invention.

Description of drawings

Fig. 1 is a flow chart of the preparation process of a polymer shaped phase-change material with evenly distributed heat-conducting fillers of the present invention;

Fig. 2 is the top view of the polymer shaped phase change material sample with PEG/PMMA/CNT thermally conductive filler evenly distributed;

Fig. 3 is a cross-sectional view of a polymer shaped phase change material sample in which PEG/PMMA/CNT thermally conductive fillers are evenly distributed.

Detailed ways

The following describes the preferred embodiments of the present invention with reference to the accompanying drawings to make the technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the protection scope of the present invention is not limited to the embodiments mentioned herein.

Example 1:

(1) Weigh 5ml of polymer monomer (MMA) and 10mg of initiator (AIBN), add them into a three-necked flask, mix and stir at 70°C and 150rpm, and perform a prepolymerization reaction for 30 minutes;

(2) Add the organic phase change material polyethylene glycol (PEG) into the flask and mix and stir for 15 minutes until fully dissolved;

(3) Continue the constant temperature polymerization reaction at 60°C for 60 minutes until the system reaches a certain viscosity; the viscosity here in this embodiment is that the viscosity is 100mPa·s

(4) Add the thermally conductive filler CNT into the flask, mix and stir at 60°C and 400rpm for 15 minutes until fully mixed;

(5) Pour the mixed solution in the three-necked flask into a square mold with a size of 40mm×40mm, and keep it in a vacuum drying oven for 20 minutes at a vacuum of 1 bar to fully remove air bubbles;

(6) The sample was subjected to a high-temperature curing reaction for 4 hours in a vacuum oven at 80° C., and then demolded after cooling at room temperature to obtain a polymer shaped phase change material with uniform distribution of thermally conductive fillers.

in,

Step (3) is a process of performing a constant temperature polymerization reaction for a period of time before adding the thermally conductive filler. The specific length of time is adjusted in conjunction with the material properties of the specific application. The longer the step is carried out, the higher the conversion rate of the in-situ polymerization reaction. The higher the viscosity of the solution, the agglomeration behavior of the carbon material under random motion and the sinking behavior under the action of gravity can be suppressed after the step (5) after the stirring is completed, so that the carbon material can be uniformly dispersed in the whole system.

If the viscosity in step (3) is too high, it will lead to insufficient defoaming in step (5). Therefore, it is necessary to determine a reasonable viscosity in step (3) to ensure the uniform distribution of carbon materials and ensure the smooth completion of defoaming. Among them, the suitable viscosity range is 65-190mPa·s

The final material has no delamination phenomenon, and the CNT thermal conductive filler presents a good uniform distribution shape, and the surface is smooth, which fully eliminates air bubbles, which is conducive to strengthening the comprehensive thermal conductivity of the material; at the same time, according to the actual energy storage requirements, the material is demoulded. Finally, it is easy to assemble and simplifies the production process.

As shown in Figure 1, a preparation process of a polymer shaped phase change material with uniform distribution of thermally conductive fillers is carried out by prepolymerizing the polymer monomer and the initiator, then adding the organic phase change material to stir and dissolve, and then carrying out constant temperature Polymerize until the system reaches a certain viscosity, then add thermally conductive filler and stir evenly, then pour the mixed solution into the mold and place it in a vacuum drying oven to remove air bubbles, and then make the sample undergo high-temperature curing reaction, cool and demould.

As shown in Figure 2, the top view of the polymer shaped phase change material sample with PEG/PMMA/CNT thermally conductive filler uniformly distributed. As shown in Figure 3, a cross-sectional view of a polymer shaped phase change material sample with PEG/PMMA/CNT thermally conductive filler uniformly distributed. It can be seen from the figure that the final material obtained has no delamination phenomenon, and the CNT thermal conductive filler presents a good uniform distribution shape and a smooth surface.

The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make many modifications and changes according to the concept of the present invention without creative efforts. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art shall be within the scope of protection defined by the claims.

Claims (10)

1. A preparation process for polymer shaped phase-change materials with uniform distribution of thermally conductive fillers, characterized in that its preparation comprises the following steps: (1) Take a certain amount of macromolecular monomer and initiator, add in the there-necked flask, mix and stir at a certain temperature and carry out prepolymerization; (2) adding the organic phase change material into the flask and mixing and stirring until fully dissolved; (3) Continue constant temperature polymerization at a certain temperature until the system reaches a certain viscosity; (4) Add the thermally conductive filler into the flask, mix and stir under the above conditions until fully mixed; (5) Pour the mixed solution in the three-necked flask into the mould, and keep it for a period of time with a certain degree of vacuum in a vacuum oven to fully remove the air bubbles; (6) Place the mold containing the mixed solution in step (5) in a vacuum drying oven to subject the sample to a high-temperature curing reaction, and then demoulding after cooling at room temperature to obtain a polymer shaped phase change material with uniform distribution of thermally conductive fillers. 2. The process for preparing a polymer shaped phase-change material with evenly distributed thermally conductive fillers according to claim 1, wherein the polymer monomer in step (1) is selected from MMA. 3 . The process for preparing a polymer shaped phase-change material with evenly distributed thermally conductive fillers according to claim 1 , wherein the initiator in step (1) is selected from AIBN. 4 . 4 . The process for preparing polymer shaped phase change materials with evenly distributed thermally conductive fillers according to claim 1 , wherein the prepolymerization reaction temperature in step (1) is 70-80° C. 5 . The process for preparing a polymer shaped phase change material with evenly distributed thermally conductive fillers according to claim 1 , wherein the prepolymerization reaction time in step (1) is 30 minutes. 6 . 6. The preparation process of a polymer shaped phase-change material with evenly distributed heat-conducting fillers according to claim 1, wherein the organic phase-change material in step (2) is selected from polyethylene glycol (PEG), paraffin wax (PA), fatty acids. 7. The preparation process of a polymer shaped phase change material with uniform distribution of thermally conductive fillers according to claim 1, characterized in that step (3) is a process of constant temperature polymerization reaction for a period of time before adding thermally conductive fillers, the specific time The length is adjusted in combination with the material properties of the specific application. The longer the step is carried out, the higher the conversion rate of the in-situ polymerization reaction is, and the higher the solution viscosity is, this can inhibit the step (5) after the completion of stirring and the carbon material in the absence of The agglomeration behavior under regular motion and the sinking behavior under the action of gravity can realize the uniform dispersion of carbon materials in the whole system. If the viscosity in step (3) is too high, it will lead to insufficient defoaming in step (5). Therefore, it is necessary to determine a reasonable viscosity in step (3) to ensure the uniform distribution of carbon materials and ensure the smooth completion of defoaming. 8. The preparation process of a polymer shaped phase change material with uniform distribution of thermally conductive fillers according to claim 1, wherein the thermally conductive fillers are selected from the group consisting of CNT, carbon nanofibers, carbon fibers, graphene, expanded graphite. 9. The preparation process of a polymer shaped phase change material with uniform distribution of thermally conductive fillers according to claim 1, characterized in that the temperature of the high-temperature curing reaction in step (6) is 80° C., and the reaction time is 4 hours. 10. A polymer shaped phase-change material with uniform distribution of thermally conductive fillers, characterized in that it is produced by the preparation process as claimed in claim 1.