Lightweight heat-conducting material with orientation structure as well as preparation method and application of lightweight heat-conducting material

Abstract

The invention provides a light heat conduction material with an orientation structure and a preparation method and application thereof, and the preparation method comprises the following steps: in a water bath, dropwise adding a sodium citrate solution into a PVA solution for salting-out flocculation, putting a flocculated sample into a long-strip-shaped polytetrafluoroethylene mold, freezing in a refrigerator, taking out, and drying to obtain the light heat conduction material with the orientation structure. And repeatedly extruding the frozen sample in a rolling device to form the FFR high polymer material with a layer-by-layer orientation structure. The prepared product has a lamellar orientation structure and excellent mechanical properties, the mechanical strength and elasticity of a high polymer material are improved, the toughness and tensile strength of the material are enhanced, the endurance capacity of the high polymer material under external stress is improved, high shape stability is kept, the tensile strength is 41.29 MPa, the strain is 500%, the Young modulus is 73.61 MPa, and the toughness is 159.37 MJ / m < 3 >. The preparation method is simple and rapid, and compared with a traditional freeze thawing method, the time is shortened to 30 min from the original 24 h or above, and the preparation efficiency is obviously improved; particularly, the prepared product is light in weight and has good heat-conducting property.

Description

Technical Field

[0001] This application belongs to the technical field of functional polymer materials, and particularly relates to a lightweight thermal conductive material with an oriented structure, its preparation method and application. Background Art

[0002] With the continuous development of electronic devices and the increasing requirements for lightweight and thermal conductivity in fields such as automobiles, aerospace, etc., the research and development of lightweight and highly efficient thermal conductive materials have become an important research direction in the field of materials science. Traditional thermal conductive materials, such as metal materials, although having good thermal conductivity, in many application scenarios, due to their high density and heavy mass, it is difficult to meet the requirements of lightweight design. Especially with high electrical conductivity, it is very likely to cause a short circuit in the circuit, thus affecting the entire device. In addition, some non-metallic materials such as ceramics, polymers, etc., although having good lightweight characteristics, their thermal conductivity is usually poor, which limits their application in high-efficiency heat dissipation and thermal management systems.

[0003] To overcome these limitations, in recent years, the research on lightweight thermal conductive materials has mainly focused on the design and development of materials with high thermal conductivity and low density. Especially polymer-based composites, due to their good processability and tunability, have become important research objects. However, most of the existing lightweight thermal conductive materials have problems such as poor thermal conductivity, difficulty in regulating the thermal conductivity, and uneven heat conduction.

[0004] In this context, the development of a lightweight thermal conductive material with an oriented structure has become a research hotspot. The oriented structure can improve the thermal conductivity of the material in a certain direction by adjusting its microstructure. Specifically, the oriented structure can effectively improve the arrangement of molecules or crystals in the material, enabling heat to propagate more efficiently along a specific direction within the material, thereby improving the overall thermal conductivity. Currently, the specific methods for achieving an anisotropic structure in polymer materials mainly include: directional freezing, composite fiber materials, mechanical training, pre-stretching, spinning, etc. However, the existing methods for achieving an anisotropic structure in synthetic polymer material systems are cumbersome and time-consuming, and are relatively poor in terms of anisotropic structure and mechanical properties. Therefore, the development of a lightweight material that not only has an oriented structure but also excellent thermal conductivity and mechanical properties can not only meet the requirements of lightweight and high-efficiency heat dissipation but also play an important role in fields such as electronic devices, automobiles, and aerospace. Summary of the Invention

[0005] This application is carried out in view of the above problems, and its purpose is to provide a preparation method for simply and quickly realizing a lightweight thermal conductive polymer material with an oriented structure. The present invention realizes the ordered arrangement of a polyvinyl alcohol (PVA) polymer network through a "flocculation - freezing - rolling" strategy, achieving an anisotropic structure and high-strength, high-toughness, and fracture-resistant mechanical properties.

[0006] The first aspect of the present application provides a method for preparing a lightweight heat-conducting material with an oriented structure, comprising the following steps: under a water bath condition, adding a sodium citrate solution dropwise to a PVA solution for salting-out flocculation, putting the flocculated sample into a long-strip-shaped polytetrafluoroethylene mold, freezing it in a refrigerator, and repeatedly extruding the frozen sample in a rolling device to form an FFR polymer material with a layer-by-layer oriented structure.

[0007] In any embodiment, the water bath temperature is 70-100 °C; the final water content of the FFR polymer material with a layer-by-layer oriented structure is controlled at 35-50%.

[0008] In any embodiment, the volume ratio of the PVA solution to the sodium citrate solution is 10:1-5, the concentration of sodium citrate is 1-1.7 mol / L, and the mass fraction of the PVA solution is 10-15 wt%.

[0009] In any embodiment, it is frozen in a -20 °C refrigerator for about 30 min.

[0010] In any embodiment, the rolling device is set at a temperature of 50-60 °C and a rotation speed of 5-20 r / min ； The roller spacing of the rolling device is 1-2.5 mm smaller than the thickness of the sample before rolling, and the final thickness of the sample is less than 2 mm.

[0011] In any embodiment, the preparation of a 15 wt% polyvinyl alcohol solution: Weigh 15 g of polyvinyl alcohol powder and place it in a beaker, add 85 g of deionized water, and stir and heat it at 90 °C in a water bath environment for 3 hours to obtain a 15 wt% polyvinyl alcohol solution.

[0012] The second aspect of the present application further provides a lightweight heat-conducting material with an oriented structure, which is an FFR polymer material obtained by the above preparation method.

[0013] The third aspect of the present application further provides an application of a lightweight heat-conducting material with an oriented structure in energy storage, tissue engineering, environmental engineering, and heat dissipation engineering.

[0014] In any embodiment, in the heat dissipation engineering, it is used in the preparation of radiators or temperature sensors for automobiles, photovoltaics, new energy batteries, and chips.

[0015] The fourth aspect of the present application further provides a chip radiator, and the heat dissipation fins of the chip radiator are prepared from the above FFR polymer material.

[0016] Advantages of the present invention:

[0017] 1) Excellent mechanical properties. The tensile strength of FFR is 41.29 MPa, the strain is 500%, the Young's modulus is 73.61 MPa, and the toughness is 159.37 MJ / m3. Compared with the FT polymer material formed by direct freeze-thaw, the tensile strength is increased by 1200 times, the Young's modulus is increased by 14000 times, and the toughness is increased by 1500 times. And it exceeds the mechanical properties of most polymer materials reported currently.

[0018] 2) The preparation method is simple and fast. Compared with forming a gel from PVA by the freeze-thaw method and then soaking it in a salt solution of a certain concentration, which usually takes more than 24 hours. This application adopts the method of salting-out flocculation first, then freezing and finally rolling and orienting. First, a sodium citrate solution of a certain concentration is dropped into a 15wt% PVA solution. Due to the Hofmeister effect, the PVA solution is salted out into flocs. Then the flocs are frozen for 30 minutes for shaping. Finally, they are repeatedly extruded in a rolling device to form a material with an oriented structure, and the preparation efficiency is significantly improved.

[0019] 3) It has a lamellar oriented structure. The lamellar oriented structure can improve the mechanical strength and elasticity of the polymer material by increasing the internal structural stability. The lamellar structure can enhance the toughness and tensile strength of the material like a laminated board, improve the tolerance of the polymer material under external stress, and help resist deformation caused by external forces, especially maintaining high shape stability when subjected to shear forces.

[0020] 4) The product has low weight and good heat dissipation. The prepared product has a density as low as 1.428 g / cm 3 3, and has good heat conduction and dissipation effects. It is especially suitable for preparing heat conduction and dissipation structures such as radiators, temperature sensors or chip heat dissipation, and is expected to be widely used in industries such as automobiles, photovoltaics, and new energy batteries. Description of the Drawings

[0021] Figure 1 is the process flow chart of the preparation method of a lightweight heat-conducting material with an oriented structure in this application;

[0022] Figure 2 is the microscopic morphology diagram of the FFR polymer material prepared in an embodiment of this application under a scanning tunneling microscope;

[0023] Figure 3 is the tensile property test diagram of the FFR polymer material prepared in this application and the FF polymer material prepared by flocculation and freezing with different orientations;

[0024] Figure 4 is the tensile fracture test diagram of the PVA polymer materials FT, FF, and FFR obtained by the preparation methods of Example 1, Comparative Example 1, and Comparative Example 2;

[0025] Figure 5 It is a performance comparison chart of the tensile strength, Young's modulus and toughness of the present application and the initial FF polymer material;

[0026] Figure 6 It is a heat transfer efficiency test chart of PVA polymer materials FT, FF and FFR obtained by the preparation methods of Example 1, Comparative Example 1 and Comparative Example 2;

[0027] Figure 7 It is an effect test chart of PVA polymer materials FT, FF and FFR obtained by the preparation methods of Example 1, Comparative Example 1 and Comparative Example 2 after being used in a chip radiator.

[0028] Figure 8 It is an application diagram of a chip radiator of the present application. Detailed implementation manners

[0029] Hereinafter, embodiments of a lightweight heat-conducting material having an oriented structure, a preparation method thereof, and an application thereof, which specifically disclose the present application, will be described in detail with reference to the drawings as appropriate. However, there may be cases where unnecessary details are omitted. For example, there may be cases where details of well-known matters are omitted and repeated descriptions of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0030] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The ranges defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, ranges of 60-110 and 80-120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "a-b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been fully listed herein, and "0-5" is only an abbreviated representation of these numerical combinations. In addition, when it is stated that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0031] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0032] Unless otherwise specified, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0033] Unless otherwise specified, all steps of the present application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out sequentially, or may also include steps (b) and (a) carried out sequentially. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may also include steps (a), (c) and (b), or may also include steps (c), (a) and (b), etc.

[0034] Unless otherwise specified, the terms "comprising" and "including" mentioned in the present application mean open-ended or may also be closed-ended. For example, the "comprising" and "including" may mean that other components not listed may also be included or comprised, or may only include or comprise the listed components.

[0035] Unless otherwise specified, in the present application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) while B is true (or exists); or both A and B are true (or exist).

[0036] A method for preparing a lightweight heat-conducting material with an oriented structure, comprising the following steps: under water bath conditions, adding a sodium citrate solution to a PVA solution for salting-out flocculation, putting the flocculated sample into a long strip-shaped polytetrafluoroethylene mold, freezing it in a refrigerator, and repeatedly extruding the frozen sample in a rolling device to form an FFR polymer material with a layer-by-layer oriented structure.

[0037] The structure of the molecular chains of a polymer determines its thermal conductivity. In a non-oriented polymer, the arrangement of the molecular chains is random, and the transfer of thermal energy mainly depends on intermolecular collisions and thermal vibrations, which results in a low thermal conductivity. By orienting the polymer molecular chains, the molecular chains can be arranged in a certain direction. This ordered structure enables heat to be propagated more efficiently along the direction of the molecular chains, thereby increasing the thermal conductivity.

[0038] Obtaining an FFR polymer material with an oriented structure layer by layer has a great influence on the thermal conductivity. Most of the moisture in the structure is removed during the rolling process, further improving the thermal conductivity and reducing the material density, making it lightweight. For example, Figure 6 It can be seen that the temperature rises significantly faster along the orientation direction.

[0039] The salting-out process is completed by dropwise adding sodium citrate, and the fluidity of the PVA solution is better in the water bath state, which is conducive to making the salting-out process more uniform.

[0040] In any embodiment, the water bath temperature is 70-100°C; the final water content of the FFR polymer material with a layer-by-layer oriented structure is controlled at 35-50%. The higher the temperature, the faster the PVA dissolves, and the PVA solution can be obtained faster.

[0041] The water content in the FFR polymer material will affect both the quality and the thermal conductivity. The less the water content, the lighter the quality and the higher the thermal conductivity. With the scheme we set, the final water content is 35-50%, preferably 46.4%. The water content should be controlled below 50% as much as possible. If it is too high, the quality will increase and the thermal conductivity will also deteriorate. To achieve a lower water content, the preparation time and difficulty will increase significantly.

[0042] In any embodiment, the volume ratio of the PVA solution to the sodium citrate solution is 10:1-5, the concentration of sodium citrate is 1-1.7 mol / L, and the mass fraction of the PVA solution is 10-15 wt%.

[0043] If the salt content is too low, flocculation cannot be formed. If the content is too high, the PVA solution will be uneven during the salting-out process, and subsequent steps cannot be carried out.

[0044] The concentration of sodium citrate is controlled at 1-1.7 mol / L. If the concentration is too low, the salt content is too low and the flocculation process cannot be completed in a short time. If the concentration is too high, the PVA solution will be uneven during the salting-out process, and subsequent steps cannot be carried out.

[0045] The PVA concentration is controlled at 10-15 wt%. If the concentration is too low, the mechanical properties of the prepared sample are poor. If the concentration is too high, the PVA cannot be dissolved.

[0046] When the concentration of sodium citrate is selected as 1.5 mol / L and the PVA concentration is 15 wt%, the finally obtained sample has both softness while maintaining strength and toughness.

[0047] In any embodiment, the sample is frozen in a -20°C refrigerator for about 30 minutes, and the sample size is 10 cm * 1.5 cm * 1 cm.

[0048] It can ensure the shaping of the sample. At a lower temperature, the corresponding freezing time is longer. If the time is too short, the sample cannot be shaped, which will affect subsequent operations. If it is too long, the sample will be completely frozen, which will also affect subsequent operations. Freezing the sample in a -20°C refrigerator for 30 minutes can make the sample completely shaped while having a suitable hardness for subsequent rolling operations. If it is too hard, the sample will be frozen into a solid state, increasing the difficulty of rolling and affecting the product quality. If the hardness is too low, it will be difficult to form during rolling. The freezing temperature can be controlled between -20°C and -5°C. According to the freezing temperature, the freezing time is controlled to make a sample with a size of 10 cm * 1.5 cm * 1 cm reach the hardness effect of being frozen in a -20°C refrigerator for about 30 minutes.

[0049] In any implementation manner, the temperature of the rolling device is set to 50 - 60°C, and the rotation speed is 5 - 20 r / min.

[0050] When the temperature is 50 - 60°C, if it is too low, the sample preparation time will increase. If it is too high, the sample will melt quickly and its shape cannot be maintained, so it cannot be rolled repeatedly. If the rotation speed is too fast, it may affect the sample, and the final orientation effect of the sample is also not good.

[0051] In any implementation manner, the distance between the rollers of the rolling device is 1 - 2.5 mm smaller than the thickness of the sample before rolling, and the final thickness of the sample is less than 2 mm.

[0052] The distance gradually decreases during rolling. Each time the sample is fed, the distance should always be less than the thickness of the sample by about 2 mm. If the distance is too large, the sample will discharge moisture under the action of heating and become completely hardened before a complete orientation is formed. If it is too small, the sample cannot enter the rolling shaft; after rolling, the sample reaches a thickness equal to the distance between the two rollers, and the distance for the next sample feeding is set to be less than the thickness of the sample by 2 mm; rolling continues until the distance between the rollers is 0 - 2 mm.

[0053] Taking the initial sample thickness of 1 cm as an example, the final distance between the two shafts is 1 mm, that is, the final thickness of the sample is 1 mm.

[0054] In any implementation manner, the preparation of a 15 wt% polyvinyl alcohol solution: Weigh 15 g of polyvinyl alcohol powder and place it in a beaker, add 85 g of deionized water, and stir and heat it in a water bath environment at 90°C for 3 hours to obtain a 15 wt% polyvinyl alcohol solution.

[0055] The second aspect of the present application also provides a lightweight heat-conducting material with an oriented structure, which is an FFR polymer material obtained by the above preparation method.

[0056] The third aspect of the present application also provides an application of a lightweight heat-conducting material with an oriented structure in energy storage, tissue engineering, environmental engineering, and heat dissipation engineering.

[0057] In any implementation, in the heat dissipation project, it is used in the preparation of radiators or temperature sensors for automobiles, photovoltaics, new energy batteries, and chips.

[0058] For example, in heat dissipation and heat conduction components for radiators or temperature sensors, it can be attached or laminated on the heat dissipation and heat conduction components, or directly prepared into heat dissipation and heat conduction components to improve heat dissipation and heat conduction effects.

[0059] The fourth aspect of the present application also provides a chip radiator, and the heat dissipation fins of the chip radiator are prepared from the above-mentioned FFR polymer material.

[0060] For example, the heat dissipation fins of the chip are directly prepared from the FFR polymer material of the present application (such as Figure 8 ), or the surface of the heat dissipation fins is attached with the FFR polymer material of the present application. While ensuring the heat dissipation effect, the overall weight of the radiator is reduced, making the product lightweight, and it can also avoid the short circuit of the circuit caused by the existing metal heat dissipation fins, thus affecting the entire device.

[0061] Examples

[0062] Hereinafter, the examples of the present application will be described. The examples described below are exemplary and are only used to explain the present application and should not be construed as a limitation to the present application. For those not specified in the examples regarding specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in the field or according to the product specifications. For the reagents or instruments not specified in the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0063] Example 1

[0064] A preparation method of a lightweight heat-conducting material with an oriented structure. Under the condition of a water bath at 95 °C, 6 mL of 1.5 mol / L sodium citrate solution was dropped into 20 mL of 15 wt% PVA solution. The PVA solution was salted out and flocculated. The flocculated sample was put into a long strip-shaped polytetrafluoroethylene mold and frozen in a -20 °C refrigerator for 30 min. The frozen sample was repeatedly extruded in a rolling device to form an FFR polymer material with a layer-by-layer oriented structure. The temperature of the rolling device was set at 60 °C, the rotation speed was 7 r / min, and the distance between the two rollers was finally controlled to be less than 2 mm.

[0065] Example 2

[0066] A preparation method of a lightweight heat-conducting material with an oriented structure. Stir 40 mL of a 15 wt% polyvinyl alcohol solution under the condition of heating in a water bath at 85 °C, and take 12 mL of a 1.5 M sodium citrate solution. Then, add the sodium citrate solution dropwise to the polyvinyl alcohol solution. Put the flocculated sample into a long strip-shaped polytetrafluoroethylene mold, freeze it in a refrigerator at -20 °C for 30 min, and repeatedly extrude the frozen sample in a rolling device to form an FFR polymer material with a layer-by-layer oriented structure. The rolling device is set at a temperature of 55 °C and a rotation speed of 5 r / min, and the distance between the two rollers is finally controlled to be less than 2 mm.

[0067] Example 3

[0068] A preparation method of a lightweight heat-conducting material with an oriented structure. Stir 10 mL of a 10 wt% polyvinyl alcohol solution under the condition of heating in a water bath at 85 °C, and take 5 mL of a 1.2 M sodium citrate solution. Then, add the sodium citrate solution dropwise to the polyvinyl alcohol solution. Put the flocculated sample into a long strip-shaped polytetrafluoroethylene mold, freeze it in a refrigerator at -20 °C for 30 min, and repeatedly extrude the frozen sample in a rolling device to form an FFR polymer material with a layer-by-layer oriented structure. The rolling device is set at a temperature of 60 °C and a rotation speed of 10 r / min, and the distance between the two rollers is finally controlled to be less than 1 mm.

[0069] Example 4

[0070] A preparation method of a lightweight heat-conducting material with an oriented structure. Stir 40 mL of a 15 wt% polyvinyl alcohol solution under the condition of heating in a water bath at 100 °C, and take 12 mL of a 1.7 M sodium citrate solution. Then, add the sodium citrate solution dropwise to the polyvinyl alcohol solution. Put the flocculated sample into a long strip-shaped polytetrafluoroethylene mold, freeze it in a refrigerator at -20 °C for 30 min, and repeatedly extrude the frozen sample in a rolling device to form an FFR polymer material with a layer-by-layer oriented structure. The rolling device is set at a temperature of 55 °C and a rotation speed of 15 r / min, and the distance between the two rollers is finally controlled to be less than 1.5 mm.

[0071] Comparative Example 1

[0072] Prepare a polyvinyl alcohol polymer material by the freeze-thaw method: Pour 20 mL of a 15 wt% polyvinyl alcohol solution into a polytetrafluoroethylene mold, freeze it in a refrigerator at -20 °C for 24 h, then take out the frozen sample and thaw it at room temperature for 3 h to obtain a (Freezing-thawing, FT) polymer material.

[0073] Comparative Example 1

[0074] Preparation of polyvinyl alcohol polymer materials by flocculation and freezing method: Stir 40 mL of 15 wt% polyvinyl alcohol solution in a water bath at 95 °C, and take 12 mL of 1.5 M sodium citrate solution. Then, add the sodium citrate solution dropwise to the polyvinyl alcohol solution. Put the flocculated sample into a polytetrafluoroethylene mold, freeze it in a refrigerator at -20 °C for 24 h, and then take out the frozen sample and thaw it at room temperature for 3 h to obtain the (Flocculation-freezing, FF) polymer material.

[0075] As Figure 1 For the preparation process flow, dissolve PVA to obtain a clear solution (Figure i); drop the transparent sodium citrate solution into the PVA aqueous solution and stir continuously until flocculation occurs, forming a white, soft polymer material in the shape of plasticine (Figure ii); this is because the Hofmeister effect is utilized. After the salt solution is dropped into the polymer solution, the polymer concentration increases and additional chain entanglements occur, promoting the formation of a large number of hydrogen bonds between PVA chains, thereby forming rich crystalline domains.

[0076] Then, shape, freeze the polymer material and apply rolling pressure to gradually orient each layer under the action of shear force (Figure iii). During the initial shear process, the water in the outermost layer of the frozen PVA gel block in contact with the heating roller axis evaporates, and at this time, the outermost dense honeycomb-like pore wall composed of closely arranged polymer chains is formed. This process results in the formation of a hard layer with an oriented structure on the upper and lower outer surfaces of the polymer material, while the middle part remains unoriented and soft. Subsequently, during the next rolling process, the hard outer layer applies a shear force to the softer inner layer in the middle, thereby inducing a new oriented structure in the inner layer. This process is repeated until the entire polymer material becomes an anisotropic FFR polymer material with a lamellar oriented structure.

[0077] As Figure 2 , The scanning electron microscope (SEM) image of the FFR polymer material prepared in this application shows a compact lamellar structure with obvious anisotropy. The cross-section parallel to the L direction (L view) highlights the highly arranged microstructure (Figures i and ii). In addition, the R view (ii-vi) cut along the R direction shows a strong hydrogen bond interaction between the stacked layers. When stretching with a pre-crack along the orientation direction, it can be seen that the lamellar structure is pulled out, which can prove the tight stacking between the lamellae.

[0078] Tensile tests were performed on two samples of FF and FFR along the orientation direction (FF|| and FFR||) and perpendicular to the orientation direction (FF⊥ and FFR⊥). The results show that there are significant differences in the mechanical properties of FFR in the two directions, indicating that FFR has a highly ordered hierarchical structure. Since the FF sample has an isotropic structure, there is no difference between the orientation direction and the perpendicular orientation direction.

[0079] Mechanical property tests were performed on the three products of Example 1, Comparative Example 1, and Comparative Example 2. The FT and FF polymer materials were used as control groups for testing. The results show that FFR has good mechanical properties. Tensile fracture tests were carried out on FT, FF, and FFR ( Figure 4 ), and it can be seen that the FT polymer material prepared by freeze-thaw has good strain properties but low strength. After flocculation treatment of FF, the mechanical properties are improved, and both strain and stress increase. This shows that both salting-out and freezing methods increase the crystallization of PVA molecular chains. After being repeatedly extruded by a rolling device, the tensile strength of the FFR polymer material is 41.29 MPa, the Young's modulus is 73.61 MPa, and the toughness is 159.37 MJ / m3. Compared with the initial FF polymer material, the tensile strength, Young's modulus, and toughness are increased by 1200 times, 14000 times, and 1500 times respectively ( Figure 5 ).

[0080] As Figure 6 , the products prepared in Example 1, Comparative Example 1, and Comparative Example 2 were placed on the same heating table, and the temperature change at the top of the sample was observed within the same time. The temperature at the top of the FFR of this application rises the fastest along the orientation direction, indicating that the heat conduction efficiency of FFR along the orientation direction is the highest.

[0081] For practical applications, the different materials of Example 1, Comparative Example 1, and Comparative Example 2 were used as chip radiators. The radiator made of FFR of this application has the most obvious cooling effect, and the temperature reduction of the chip exceeds that of commercially available radiators.

[0082] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and embodiments with the same structure and the same function and effect as the technical idea within the technical solution scope of this application are all included in the technical scope of this application. In addition, within the scope of not departing from the main idea of this application, various deformations that those skilled in the art can think of for the embodiments, and other ways constructed by combining some constituent elements of the embodiments are also included in the scope of this application.

Claims

1. A method for preparing a lightweight thermally conductive material with an oriented structure, characterized in that: The following steps are involved: Under water bath conditions, sodium citrate solution is added to the PVA solution for salting out and flocculation. The flocculated sample is placed in a long polytetrafluoroethylene mold and frozen in a refrigerator. The frozen sample is repeatedly extruded in a roller pressing device to form a FFR polymer material with a layer-by-layer oriented structure.

2. The method for preparing a lightweight thermally conductive material with an oriented structure according to claim 1, characterized in that: The water bath temperature is 70-100° C.; the final water content of the FFR polymer material with layer-by-layer orientation structure is controlled at 35-50%.

3. The method for preparing a lightweight thermally conductive material with an oriented structure according to claim 1, characterized in that: The volume ratio of the PVA solution to the sodium citrate solution is 10:1-5, the concentration of sodium citrate is 1-1.7 mol / L, and the mass fraction of the PVA solution is 10-15 wt %.

4. The method for preparing a lightweight thermally conductive material with an oriented structure according to claim 1, characterized in that: The freezing is carried out in a -20°C refrigerator for about 30 minutes; the roller pressing device is set at a temperature of 50-60°C and a rotation speed of 5-20 r / min.

5. The method for preparing a lightweight thermally conductive material with an oriented structure according to claim 1 or 4, characterized in that: The roller spacing of the rolling device is 1-2.5 mm smaller than the thickness of the sample before rolling, and the final thickness of the sample is less than 2 mm.

6. The method for preparing a lightweight thermally conductive material with an oriented structure according to claim 3, characterized in that: Preparation of the 15 wt % polyvinyl alcohol solution: weigh 15 g of polyvinyl alcohol powder and put it in a beaker, add 85 g of deionized water, and heat at 90° C. in a water bath with stirring for 3 hours to obtain a 15 wt % polyvinyl alcohol solution.

7. A light thermal conductive material with an oriented structure, an FFR polymer material obtained by the method for preparing a light thermal conductive material with an oriented structure as claimed in any one of claims 1 to 7.

8. A method for preparing a lightweight thermally conductive material with an oriented structure as described in any one of claims 1 to 6 or an application of the FFR polymer material as described in claim 7 in energy storage, tissue engineering, environmental engineering and heat dissipation engineering.

9. The use of a lightweight thermally conductive material with an oriented structure as claimed in claim 8, wherein the heat dissipation project is used in the preparation of heat sinks or temperature sensors for automobiles, photovoltaics, new energy batteries, and chips.

10. A chip heat sink, wherein the heat dissipation fins of the chip heat sink are prepared by the preparation method of a lightweight thermal conductive material with an oriented structure as described in any one of claims 1 to 6 or the FFR polymer material as described in claim 7.

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