Conductive gel material, heat-conducting nylon material and preparation methods of conductive gel material and heat-conducting nylon material

Abstract

The invention discloses a conductive gel material with a stable structure, a heat-conducting nylon material and a preparation method thereof. The conductive gel material is prepared by dispersing h-BN powder into a solvent to obtain a lamellar h-BN material with a stripped lamellar layer, and then adding a lignocellulose solution and dichloroisocyanuric acid for post-treatment. And preparing the heat-conducting nylon material from the caprolactam prepolymer and the cellulose-boron nitride gel material through an in-situ polymerization method. Under the condition that the addition amount of the conductive gel material is low, the thermal conductivity of the nylon material in the plane direction and the thickness direction can be remarkably improved. The heat conductivity coefficient of the final nylon material in the plane direction reaches 16.2-18.5 W / mK, and the heat conductivity coefficient in the thickness direction reaches 16.6-18.4 W / mK. The material can be widely applied to special fields of electronic appliances, household appliances, military industry and the like.

Description

Technical Field

[0001] The present invention relates to the field of material modification, and particularly to a conductive gel material, a thermally conductive nylon material and a preparation method thereof. Background Art

[0002] Heat dissipation is crucial for the performance and lifespan of integrated electronic devices, because the reliability of electronic devices has an exponential dependence on the operating temperature, and the lifespan of electronic devices with excellent heat dissipation can be greatly improved.

[0003] Due to its high mechanical properties and high temperature resistance, nylon materials are often used in electronic and electrical components. However, plastics themselves have poor thermal conductivity. Even if thermal conductive fillers such as silica are added to modify nylon materials, the final thermal conductivity of nylon materials cannot reach 0.5 W / mK. Other polymer composites filled with ceramic or metal fillers have high thermal conductivity, but require very high filler addition ratios, resulting in deteriorated processability and increased weight of the materials. So far, the lack of new thermal conductive materials has been one of the main challenges for future high-power density electronic products.

[0004] Hexagonal boron nitride (h-BN) is called "white graphene" because it has a hexagonal atomic structure similar to that of graphene. Different from carbon atoms in graphene, h-BN consists of alternating boron atoms and nitrogen atoms in a honeycomb structure. Hexagonal boron nitride nanosheets have an ultra-high thermal conductivity (about 2000 W / mK). However, when this material is used in the field of modified plastics, due to the poor dispersibility of h-BN in plastics, it will cause large thermal conductivity anisotropy in plastics, resulting in unstable thermal conductivity of the final material. In addition, in the current conventional twin-screw extrusion processing method, since the processing process is a simple physical blending, the dispersion effect of the twin-screw is limited, and for the parts made by injection molding, the fillers are easily arranged along the gate direction. Although the in-plane thermal conductivity of the material has been greatly improved, however, the improvement of the thermal conductivity through the thickness is mostly limited, which is mainly due to the orientation problem of the fillers, making it difficult to construct a thermal conduction channel in the thickness direction of the material. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a conductive gel material, a thermally conductive nylon 66 material and a preparation method thereof to solve various technical problems of existing nylon products.

[0006] The present invention can be realized by the following technical solutions: The first object of the present invention is to provide a preparation method of a conductive gel material with stable structure, which includes the following steps: (1) Adding h-BN powder into a solvent for ultrasonic dispersion to obtain a suspension, then performing centrifugal separation, and collecting the supernatant; (2) Redisperse the collected supernatant in the solvent by ultrasonic treatment again, and then perform centrifugation to collect the precipitate. (3) Dry the precipitate to obtain the exfoliated flaky h-BN material. (4) Add the dried lignocellulose to the alkaline solution and stir, then add dichloroisocyanuric acid and the flaky h-BN material and continue stirring. (5) After the lignocellulose is completely dissolved, pour it into a mold together, and dry and let it stand to obtain a gel. (6) Wash the gel with deionized water. After completely removing the residual solvent inside the gel, place it in a freeze dryer under nitrogen protection for treatment to obtain the cellulose-boron nitride gel material.

[0007] Further, in step (1), the mass-volume ratio of the h-BN powder to the solvent is 2 g:(100 - 200) ml. The solvents in steps (1) and (2) are both isopropyl alcohol aqueous solutions, where the volume ratio of isopropyl alcohol to water is 1:0.5 - 1.5.

[0008] Further, in step (3), the drying of the precipitate is to place the precipitate in a vacuum oven at 50°C - 70°C for drying. Further, in step (4), the alkaline solution is prepared by mixing sodium hydroxide, urea and deionized water in a mass ratio of 6 - 9:10 - 14:77 - 84. The mass ratio of lignocellulose, flaky h-BN material, dichloroisocyanuric acid and alkaline solution is (2 - 5):(3 - 6):(2 - 4):100.

[0009] Further, in step (5), the drying and standing is to place the mold containing the solution in an oven at 45 - 60°C for 2 - 5 hours. In step (6), wash with deionized water 5 - 10 times. The temperature in the freeze dryer is -60 to -90°C, and the treatment time is 40 - 60 hours.

[0010] The second object of the present invention is to provide a conductive gel material, which is the cellulose-boron nitride gel material prepared above.

[0011] The third object of the present invention is to provide a thermally conductive nylon material, which is obtained by in-situ polymerization of the conductive gel material and caprolactam prepolymer. The conductive gel material is the cellulose-boron nitride gel material prepared above, and the addition amount of the conductive gel material accounts for 3 - 10% of the total mass of the thermally conductive nylon material.

[0012] It should be particularly noted that the caprolactam prepolymer in the present invention cannot be stored for a long time and needs to be injected into the cellulose-boron nitride gel material within 30 s after preparation for in-situ polymerization reaction.

[0013] In a further embodiment, the caprolactam prepolymer is prepared by the following steps: (1) Heating the solid powder of caprolactam to complete melting under nitrogen protection, maintaining the temperature, evacuating to negative pressure to remove all the moisture in the raw materials until the moisture content in the system < 500 ppm; (2) Adding a catalyst and an activator, and starting negative pressure evacuation to remove the moisture generated in the system until the moisture content < 500 ppm; (3) Reacting the solid to obtain the caprolactam prepolymer.

[0014] In a further embodiment, the catalyst is one of sodium hydroxide, magnesium bromide caprolactam or C10, and its addition amount is 0.1%-3% of the mass of the solid powder of caprolactam.

[0015] The activator is one of 2,4-toluene diisocyanate TDI, diphenylmethane diisocyanate MDI or C20, and its addition amount is 0.1-3% of the mass of the solid powder of caprolactam.

[0016] In a further embodiment, the cellulose-boron nitride gel material is placed in a mold, the caprolactam prepolymer is injected, and it is kept warm in an oven at 130 °C to 180 °C for 20-60 min, taken out and cooled to obtain the thermally conductive nylon material.

[0017] The cellulose-boron nitride gel material prepared in the present invention is a layered material obtained by exfoliating h-BN powder into flakes, making it have higher spatial freedom and dispersion effect. Then the flaky h-BN material and cellulose are prepared into a gel, and the three-dimensional spatial effect is supported by the network structure of cellulose, and the flaky h-BN is dispersed therein, so that the gel material has isotropic thermal conductivity. At the same time, dichloroisocyanuric acid is used as a cross-linking agent to cross-link the hydroxyl groups of cellulose with the hydroxyl and amino groups on the flaky h-BN to prepare a structurally stable conductive gel material.

[0018] The present invention in-situ polymerizes the structurally stable conductive gel material and the caprolactam prepolymer to obtain a nylon material, significantly improving the thermal conductivity of the nylon material.

[0019] The preparation of the present invention is a polymerization process, which is different from the traditional method of obtaining parts by twin-screw extrusion and injection molding. To ensure that the 3D structure of the gel material is not damaged, the present invention adopts an in-situ polymerization method, injecting the caprolactam prepolymer into the conductive gel material and then polymerizing it into a conductive nylon material.

[0020] In the present invention, the addition amount of the cellulose-boron nitride gel material is small, only 3-10% of the total mass of the thermally conductive nylon material, but it can significantly improve the thermal conductivity of the nylon material in the plane direction and the thickness direction. The thermal conductivity of the final nylon material in the plane direction reaches 16.2-18.5 W / mK, and the thermal conductivity in the thickness direction reaches 16.6-18.4 W / mK. Specific Embodiments

[0021] The following shows the embodiments of the present invention for specific description, but the present invention is not limited by these embodiments. Referring to the following embodiments and combining the description of the preparation and testing techniques and the materials used, the present invention can be better understood.

[0022] In the following embodiments, the following various raw materials are preferably used: Caprolactam, Grodno Azot h-BN powder, Shanghai Zhuzi New Materials Co., Ltd. Sodium hydroxide, TDI, MDI, isopropanol, dichloroisocyanuric acid, Shanghai Chemical Reagent Company, China National Pharmaceutical Corporation Magnesium bromide caprolactam, C10, C20, Bruggemann Wood cellulose, Sigma-Aldrich Example 1: Put 3 parts of the prepared cellulose-boron nitride gel material into a mold, inject 97 parts of caprolactam prepolymer, keep it warm in an oven at 160 °C for 40 min, take it out and cool it to obtain a thermally conductive nylon material.

[0023] Among them, the cellulose-boron nitride gel material is prepared by the following steps: (1) Take 2 g of commercially available h-BN powder and add it to 150 ml of an isopropanol aqueous solution (composed of isopropanol and distilled water in a volume ratio of 1:1), and ultrasonically treat it for 20 h; (2) Centrifuge the above suspension to remove the precipitate and collect the supernatant; the supernatant contains the exfoliated flaky h-BN material; (3) Disperse the collected supernatant again in a mixed solution of 150 ml of isopropanol and distilled water, and ultrasonically disperse it for 20 h, where the volume ratio of isopropanol to distilled water is 1:1; (4) Centrifuge the above suspension, collect the precipitate, and dry the precipitate in a vacuum oven at 60 °C. The obtained product is the exfoliated flaky h-BN material; (5) Cut the wood cellulose raw material into small pieces and dry it in an oven at 80 °C for 24 h; (6) Prepare a solution by mixing sodium hydroxide, urea, and deionized water in a certain ratio, where the mass ratio of sodium hydroxide, urea, and deionized water is 8:12:80; add the treated lignocellulose, flaky h-BN material, and dichloroisocyanuric acid to this solution, with the mass ratio of lignocellulose:solution = 4:100, flaky h-BN material:solution = 5:100, and dichloroisocyanuric acid:solution mass ratio = 3:100; (7) After the lignocellulose in the above step is completely dissolved, place it in a stainless-steel mold, and place the solution in an oven at 50 °C for 4 hours to obtain a gel; (8) Wash the gel 6 times with deionized water to completely remove the residual solvent inside the gel. Under nitrogen protection, place it in a freeze dryer and treat it at -80 °C for 50 hours to obtain a cellulose-boron nitride gel material.

[0024] Among them, the caprolactam prepolymer is prepared by the following steps: (1) Heat a certain amount of solid caprolactam powder to 120 °C under nitrogen protection until it is completely melted. Maintain this temperature, apply a vacuum negative pressure to remove all the moisture in the raw materials until the moisture content in the system < 500 ppm; (2) Add 0.2% of the catalyst sodium hydroxide by mass of the solid caprolactam powder to the above system; turn on the negative pressure to remove the moisture generated in the system until the content < 500 ppm; (3) Continue to add 0.3% of the activator 2,4-toluene diisocyanate TDI by mass of the solid caprolactam powder to the above system; (4) React the solid to obtain a caprolactam prepolymer.

[0025] Example 2: Put 5 parts of the prepared cellulose-boron nitride gel material into a mold, inject 95 parts of the caprolactam prepolymer, keep it warm in an oven at 150 °C for 30 min, take it out and cool it to obtain a thermally conductive nylon material.

[0026] Among them, the boron nitride gel material is prepared by the following steps: (1) Take 2 g of commercially available h-BN powder and add it to a mixed solution of 180 ml of isopropanol and distilled water, and ultrasonically treat it for 15 h, where the volume ratio of isopropanol to distilled water is 1:1.2; (2) Centrifuge the above suspension to remove the precipitate and collect the supernatant; the supernatant contains the flaky h-BN material with exfoliated layers; (3) Redisperse the collected supernatant in a mixed solution of 180 ml of isopropanol and distilled water, and ultrasonically disperse it for 18 h, where the volume ratio of isopropanol to distilled water is 1:1.2; (4) Centrifuge the above suspension, collect the precipitate, and dry the precipitate in a vacuum oven at 60 °C. The obtained product is the exfoliated flaky h-BN material; (5) Cut the lignocellulosic raw material into small pieces and dry it in an oven at 80 °C for 28 h; (6) Prepare a solution with sodium hydroxide, urea, and deionized water in a certain ratio, where the mass ratio of sodium hydroxide, urea, and deionized water is 7:13:80 to obtain solution a; add the lignocellulose and flaky h-BN material treated in step (4) to this solution, with the mass ratio of lignocellulose: solution a = 4:100; with the mass ratio of flaky h-BN material: solution = 5:100; add dichloroisocyanuric acid to the above solution, where the mass ratio of dichloroisocyanuric acid: solution a = 3:100; (7) After the lignocellulose in the above step is completely dissolved, place it in a stainless-steel mold and put the solution in an oven at 50 °C for 4 hours to obtain a gel; (8) Wash the gel 8 times with deionized water to completely remove the residual solvent inside the gel. Under nitrogen protection, put it into a freeze dryer and treat it at -70 °C for 50 hours to obtain a cellulose-boron nitride gel material.

[0027] Among them, the caprolactam prepolymer is prepared by the following steps: (1) Heat a certain amount of solid caprolactam powder to 130 °C under nitrogen protection until it is completely melted. Keep this temperature, apply a vacuum negative pressure to remove all the moisture in the raw materials until the moisture content in the system < 500 ppm; (2) Add magnesium bromide caprolactam accounting for 1.5% of the mass of the solid caprolactam powder to the above system; turn on the negative pressure to pump out the moisture generated in the system until the content < 500 ppm; (3) Continue to add 2% of activator C20 by mass to the above system, turn on the negative pressure to pump out the moisture generated in the system until the content < 500 ppm; (4) React solidly to obtain the caprolactam prepolymer.

[0028] Example 3: Put 6 parts of the prepared cellulose-boron nitride gel material into a mold, inject 94 parts of the caprolactam prepolymer, keep it warm in an oven at 140 °C for 30 min, take it out and cool it to obtain a thermally conductive nylon material.

[0029] Among them, the boron nitride gel material is prepared by the following steps and ratios: (1) Take 2 g of commercially available h-BN powder and add it to a mixed solution of 120 ml of isopropanol and distilled water, and ultrasonically treat it for 10 - 24 h, where the volume ratio of isopropanol to distilled water is 1:0.8; (2) Centrifuge the above suspension to remove the precipitate and collect the supernatant; the supernatant contains the exfoliated flaky h-BN material. (3) Redisperse the collected supernatant in a mixed solution of 120 ml of isopropanol and distilled water, and ultrasonically disperse for 12 h, where the volume ratio of isopropanol to distilled water is 1:0.8. (4) Centrifuge the above suspension to collect the precipitate, and dry the precipitate in a vacuum oven at 60 °C. The product is the exfoliated flaky h-BN material. (5) Cut the lignocellulose raw material into small pieces and dry it in an oven at 75 °C for 24 h. (6) Prepare a solution with sodium hydroxide, urea and deionized water in a certain proportion, where the mass ratio of sodium hydroxide, urea and deionized water is 7:12:81; add the treated lignocellulose, flaky h-BN material and dichloroisocyanuric acid to this solution, with the mass ratio of lignocellulose: solution = 3:100; flaky h-BN material: solution = 4:100, and the mass ratio of dichloroisocyanuric acid: solution = 3:100. (7) After the lignocellulose in the above step is completely dissolved, put it into a stainless steel mold, and place the solution in an oven at 45 °C for 3 hours to obtain a gel. (8) Wash the gel 6 times with deionized water to completely remove the residual solvent inside the gel. Under nitrogen protection, put it into a freeze dryer and treat it at -70 °C for 45 hours to obtain a cellulose-boron nitride gel material.

[0030] The caprolactam prepolymer is prepared by the following steps: (1) Heat a certain amount of solid caprolactam powder to 100 °C under nitrogen protection until it is completely melted. Keep this temperature, apply a vacuum negative pressure to remove all the moisture in the raw material until the moisture content in the system < 500 ppm. (2) Add 1.5% of catalyst C10 by mass of the solid caprolactam powder in the above system; turn on the negative pressure to remove the moisture generated in the system until the content < 500 ppm. (3) Continue to add 0.3% of the activator diphenylmethane diisocyanate MDI by mass of the solid caprolactam powder in the above system, and control the moisture < 500 ppm. (4) React solid to obtain the caprolactam prepolymer.

[0031] Example 4: Put 4 parts of the prepared cellulose-boron nitride gel material into a stainless steel mold, inject 96 parts of the caprolactam prepolymer, keep it warm in an oven at 130 °C for 20 min, take it out and cool it to obtain a thermally conductive nylon material.

[0032] Among them, the boron nitride gel material is prepared by the following steps: (1) Take 2 g of commercially available h-BN powder and add it to a mixed solution of 100 ml of isopropyl alcohol and distilled water, and ultrasonically treat it for 10 h, where the volume ratio of isopropyl alcohol to distilled water is 1:0.5; (2) Centrifuge the above suspension to remove the precipitate and collect the supernatant; the supernatant contains flaky h-BN materials with exfoliated layers; (3) Disperse the collected supernatant again in a mixed solution of 100 ml of isopropyl alcohol and distilled water, and ultrasonically disperse it for 10 h, where the volume ratio of isopropyl alcohol to distilled water is 1:0.5; (4) Centrifuge the above suspension to collect the precipitate, and dry the precipitate in a vacuum oven at 50 °C. The obtained product is the flaky h-BN material with exfoliated layers; (5) Cut the lignocellulose raw material into small pieces and dry it in an oven at 70 °C for 20 h; (6) Prepare a solution with sodium hydroxide, urea and deionized water according to a ratio, where the mass ratio of sodium hydroxide, urea and deionized water is 6:10:84 to obtain solution a; add the lignocellulose and flaky h-BN materials treated in step (4) to this solution, with the mass ratio of lignocellulose: solution a = 2:100; with the mass ratio of flaky h-BN material: solution = 3:100, add dichloroisocyanuric acid to the above solution, where the mass ratio of dichloroisocyanuric acid: solution a = 2:100; (7) After the lignocellulose in the above step is completely dissolved, put it into a mold, and place the solution in an oven at 45 °C for 2 hours to obtain a gel; (8) Wash the gel 5 times with deionized water to completely remove the residual solvent inside the gel. Under nitrogen protection, put it into a freeze dryer and treat it at -60 °C for 40 hours to obtain the cellulose-boron nitride gel material.

[0033] Among them, the caprolactam prepolymer is prepared by the following steps: (1) Heat a certain amount of solid caprolactam powder to 80 °C under nitrogen protection until it is completely melted. Keep this temperature, apply a vacuum negative pressure to remove all the moisture in the raw materials until the moisture content in the system < 500 ppm; (2) Add 0.1% of the catalyst sodium hydroxide by mass of the solid caprolactam powder to the above system; turn on the negative pressure to pump out the moisture generated in the system until the content < 500 ppm; (3) Continue to add 0.1 of the activator 2,4-toluene diisocyanate TDI by mass of the solid caprolactam powder to the above system, and control the moisture < 500 ppm; (4) React solidly to obtain the caprolactam prepolymer.

[0034] Example 5: Put 7 parts of the prepared cellulose-boron nitride gel material into a stainless steel mold, inject 93 parts of the caprolactam prepolymer, keep it warm in an oven at 180 °C for 60 min, take it out and cool it to obtain a thermally conductive nylon material.

[0035] Among them, the boron nitride gel material is prepared by the following steps: (1) Take 2 g of commercially available h-BN powder and add it to a mixed solution of 200 ml of isopropanol and distilled water, and ultrasonically treat it for 24 h, where the volume ratio of isopropanol to distilled water is 1:1.5; (2) Centrifuge the above suspension to remove the precipitate and collect the supernatant; the supernatant contains the exfoliated flaky h-BN material; (3) Disperse the collected supernatant again in a mixed solution of 200 ml of isopropanol and distilled water, and ultrasonically disperse it for 24 h, where the volume ratio of isopropanol to distilled water is 1:1.5; (4) Centrifuge the above suspension, collect the precipitate, and dry the precipitate in a vacuum oven at 50 °C - 70 °C. The product is the exfoliated flaky h-BN material; (5) Cut the lignocellulose raw material into small pieces and dry it in an oven at 85 °C for 30 h; (6) Prepare a solution with sodium hydroxide, urea and deionized water according to a ratio, where the mass ratio of sodium hydroxide, urea and deionized water is 9:14:77; Add the treated lignocellulose, flaky h-BN material and dichloroisocyanuric acid to this solution, according to the mass ratio of lignocellulose:solution = 5:100; flaky h-BN material:solution = 6:100, and the mass ratio of dichloroisocyanuric acid:solution is = 4:100; (7) After the lignocellulose in the above step is completely dissolved, put it into a mold, and place the solution in an oven at 60 °C for 5 hours to obtain a gel; (8) Wash the gel 10 times with deionized water to completely remove the residual solvent inside the gel. Under nitrogen protection, put it into a freeze dryer and treat it at -90 °C for 60 hours to obtain the cellulose-boron nitride gel material.

[0036] Among them, the caprolactam prepolymer is prepared by the following steps and ratios: (1) Heat a certain amount of caprolactam solid powder to 150 °C under nitrogen protection until it is completely melted. Keep this temperature, apply a vacuum negative pressure to remove all the moisture in the raw materials until the moisture content in the system < 500 ppm; (2) Add one of the catalysts C10, which is 3% of the mass fraction of the caprolactam solid powder, to the above system; turn on the negative pressure to remove the water generated in the system until the content is <500 ppm; (3) Continue to add the activator C20, which is 3% of the mass fraction of the caprolactam solid powder, to the above system, and control the water content <500 ppm; (4) Obtain the caprolactam prepolymer through solid-state reaction.

[0037] Comparative Example 1: Mix 3 parts of the prepared cellulose-boron nitride gel material and 97 parts of nylon 6 evenly through a high-speed mixer, then process through a twin-screw extruder, extrude and granulate, and then inject the modified particles into samples.

[0038] Among them, the cellulose-boron nitride gel material is the cellulose-boron nitride gel material prepared in Example 1.

[0039] Comparative Example 2: Inject 100 parts of the caprolactam prepolymer into the mold, keep it warm in an oven at 160 °C for 40 min, take it out and cool it to obtain a thermally conductive nylon material.

[0040] Among them, the caprolactam prepolymer is the caprolactam prepolymer prepared in Example 1.

[0041] Comparative Example 3: Similar to Example 1, put 3 parts of the prepared cellulose-boron nitride gel material into the mold, inject 97 parts of the caprolactam prepolymer, keep it warm in an oven at 160 °C for 40 min, take it out and cool it to obtain a thermally conductive nylon material.

[0042] Among them, the caprolactam prepolymer is the caprolactam prepolymer prepared in Example 1; The preparation process of the cellulose-boron nitride gel material is different from that in Example 1. Specifically: (1) Take 2 g of commercially available h-BN powder and add it to a mixed solution of 150 ml of isopropanol and distilled water, and ultrasonically treat it for 20 h, where the volume ratio of isopropanol to distilled water is 1:1; (2) Centrifuge the above suspension to remove the precipitate and collect the supernatant; the supernatant contains the exfoliated flaky h-BN material; (3) Disperse the collected supernatant again in a mixed solution of 150 ml of isopropanol and distilled water, and ultrasonically disperse it for 20 h, where the volume ratio of isopropanol to distilled water is 1:1; (4) Centrifuge the above suspension to collect the precipitate, and dry the precipitate in a vacuum oven at 60 °C. The obtained product is the exfoliated flaky h-BN material; (5) Cut the lignocellulosic raw material into small pieces and dry it in an oven at 80 °C for 24 h; (6) Prepare a solution with sodium hydroxide, urea, and deionized water in a certain ratio, where the mass ratio of sodium hydroxide, urea, and deionized water is 8:12:80; add the treated lignocellulosic raw material and flaky h-BN material to this solution, with the mass ratio of lignocellulosic raw material: solution a = 4:100 and flaky h-BN material: solution = 5:100; (7) After the lignocellulosic raw material in the above step is completely dissolved, place it in a stainless-steel mold and put the solution in an oven at 50 °C for 4 hours to obtain a gel; (8) Wash the gel 6 times with deionized water to completely remove the residual solvent inside the gel. Under nitrogen protection, put it into a freeze dryer and treat it at -80 °C for 50 hours to obtain a cellulose-boron nitride gel material.

[0043] Test example: Test the thermal conductivity of the samples prepared in the above examples and comparative examples. The thermal conductivity K (W / mK) is calculated by the formula κ = α∙ρ∙Cp, where κ is the thermal conductivity, α is the thermal diffusivity (mm 2 / s), which is measured by a laser flash analyzer (LFA, Netzsch 457 micro flash), ρ is the sample density (g / cm3), and Cp is the specific heat (J / g∙K) measured by differential scanning calorimetry (TAQ200 DSC). The test environment temperature is 23 °C.

[0044]

[0045] It can be seen from the performance detected in the above table that the thermally conductive nylon materials prepared in Examples 1-5 of the present invention have excellent thermal conductivity and good thermal conductivity in both the plane direction and the thickness direction. Specifically, by comparing Example 1 with Comparative Example 1, it is found that due to the addition of the caprolactam prepolymer in Example 1, and the in-situ polymerization of the conductive gel material and the caprolactam prepolymer to obtain the nylon material, the 3D structure of the conductive gel material is ensured not to be damaged, thereby improving the thermal conductivity of the nylon material, and it has good thermal conductivity in both the plane direction and the thickness direction. For the parts obtained by twin-screw extrusion and injection molding in Comparative Example 1, it is mainly physical blending, and the dispersion effect of the twin-screw is limited. Moreover, for the parts obtained by injection molding, the fillers are easily arranged along the gate direction. Although the in-plane thermal conductivity of the material has been greatly improved, however, the improvement of the thermal conductivity through the thickness is mostly limited, mainly due to the orientation problem of the fillers, which makes it difficult to construct a thermal conduction channel in the thickness direction of the material.

[0046] Comparing Example 1 with Comparative Example 2, since no conductive gel material was added in Comparative Example 2, the thermal conductivity of the nylon material is poor, especially in the thickness direction of the material.

[0047] Comparing Example 1 with Comparative Example 3, although the cellulose-boron nitride gel material was also added in Comparative Example 3, the cross-linking agent dichloroisocyanuric acid was not added during the preparation of the cellulose-boron nitride gel material, resulting in an unstable structure of the prepared conductive gel material and unable to form a continuous three-dimensional network structure, which affects its electrical and thermal conductivity. As a result, the thermal conductivity of the final nylon material becomes poor.

[0048] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0049] The above-described embodiments merely represent several implementation manners of the present invention, and the description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A preparation method of a conductive gel material with stable structure, characterized in that: It includes the following steps: (1) Add h-BN powder into a solvent, perform ultrasonic dispersion to obtain a suspension, then conduct centrifugal separation, and collect the supernatant; (2) Redisperse the collected supernatant into the solvent by ultrasonic again, then conduct centrifugal separation, and collect the precipitate; (3) Dry the precipitate to obtain flaky h-BN material with exfoliated layers; (4) Add the dried lignocellulose into an alkaline solution and stir, then add dichloroisocyanuric acid and the flaky h-BN material and continue stirring; (5) After the lignocellulose is completely dissolved, pour it into a mold together, dry and stand still to obtain a gel; (6) Wash the gel with deionized water, completely remove the residual solvent inside the gel, then under nitrogen protection, place it in a freeze dryer for treatment to obtain a cellulose-boron nitride gel material.

2. The preparation method according to claim 1, characterized in that: In step (1), the mass-volume ratio of the h-BN powder to the solvent is 2 g:(100 - 200) ml; The solvents in steps (1) and (2) are both isopropyl alcohol aqueous solutions, and the volume ratio of isopropyl alcohol to water is 1:0.5 - 1.

5.

3. The preparation method according to claim 1, characterized in that: In step (3), the drying of the precipitate is to place the precipitate in a vacuum oven at 50°C - 70°C for drying.

4. The preparation method according to claim 1, characterized in that: In step (4), the alkaline solution is prepared by mixing sodium hydroxide, urea and deionized water according to a mass ratio of 6 - 9:10 - 14:77 - 84; The mass ratio of lignocellulose, flaky h-BN material, dichloroisocyanuric acid and the alkaline solution is (2 - 5):(3 - 6):(2 - 4):

100.

5. The preparation method according to claim 1, characterized in that: In step (5), the drying and standing still is to place the mold containing the solution in an oven at 45 - 60°C for 2 - 5 hours; In step (6), wash with deionized water 5 - 10 times, the temperature in the freeze dryer is -60°C to -90°C, and the treatment time is 40 - 60 hours.

6. A conductive gel material, characterized in that: It is the cellulose-boron nitride gel material prepared according to any one of claims 1 - 5.

7. A thermally conductive nylon material, characterized in that: It is obtained by in-situ polymerization of a conductive gel material and a caprolactam prepolymer, wherein the conductive gel material is the cellulose-boron nitride gel material prepared according to any one of claims 1 - 5, and the addition amount of the conductive gel material accounts for 3 - 10% of the total mass of the thermally conductive nylon material.

8. A thermally conductive nylon material according to claim 7, characterized in that: The caprolactam prepolymer is prepared by the following steps: (1) Heat the solid powder of caprolactam to complete melting under nitrogen protection, maintain the temperature, evacuate to negative pressure to remove all the moisture in the raw materials until the moisture content in the system < 500 ppm; (2) Add a catalyst and an activator, start evacuating the moisture generated in the system under negative pressure until the moisture content < 500 ppm; (3) React solidly to obtain the caprolactam prepolymer.

9. The thermally conductive nylon material according to claim 8, characterized in that: The catalyst is one of sodium hydroxide, magnesium bromide caprolactamate or C10, and its addition amount is 0.1% - 3% of the mass of the solid powder of caprolactam; The activator is one of 2,4-toluene diisocyanate TDI, diphenylmethane diisocyanate MDI or C20, and its addition amount is 0.1 - 3% of the mass of the solid powder of caprolactam.

10. The preparation method of a heat-conducting nylon material according to any one of claims 7-9, characterized in that: Put the cellulose-boron nitride gel material into a mold, inject the caprolactam prepolymer, keep it warm in an oven at 130°C to 180°C for 20 - 60 minutes, take it out and cool it to obtain the thermally conductive nylon material.

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