CN104559183A - Preparation method of magnetic micro/nano composite filler/silicon rubber heat-conducting composite material - Google Patents

Abstract

The invention belongs to the field of polymer-based heat-conducting composite materials, and relates to a method for preparing a heat-conducting polymer composite material, in particular to a method for preparing a magnetic micro-nano composite filler/silicone rubber heat-conducting composite material. The invention disperses and composites the magnetic nanometer metal particles on the surface of the micron-scale heat-conducting filler to prepare the magnetic composite heat-conducting filler, utilizes the micro-nano composite to bring magnetic responsiveness, and arranges and aligns the micro-nano composite filler dispersed in the silicone rubber matrix through an external magnetic field Adjusting and controlling can realize the directional arrangement of composite thermally conductive fillers in the silicone rubber matrix, and then realize the preparation of high thermally conductive silicone rubber composites with anisotropic thermal conductivity at a low filling fraction of fillers. Filler Preparation of micro-nano composite filler can avoid the problem of difficult dispersion and agglomeration of nano-metal particles in the polymer matrix, and can indirectly realize the uniform dispersion of micro-nano particles in the polymer matrix.

Description

Preparation method of magnetic micro-nano composite filler/silicone rubber heat-conducting composite material

technical field

The invention belongs to the field of polymer-based heat-conducting composite materials, and relates to a method for preparing a heat-conducting polymer composite material, in particular to a method for preparing a magnetic micro-nano composite filler/silicone rubber heat-conducting composite material.

Background technique

In recent years, with the increasing integration and miniaturization of electronic components, the resulting heat accumulation and heat dissipation have become one of the key factors restricting the reliability and service life of electronic components; Thermally conductive materials have been extensively studied to solve such problems. Polymer materials have the advantages of good electrical insulation, light weight, corrosion resistance, and easy processing, but their thermal conductivity is poor. Fillers are filled into polymer materials to improve their thermal conductivity.

There are many factors that affect the thermal conductivity of polymer materials, such as different material preparation methods, the quality of filler thermal conductivity and the level of filling, different filler shapes and sizes, different filler component ratios, and physical and chemical properties of the filler surface, etc. Both will significantly affect the thermal conductivity of the material; existing research results have shown that increasing the proportion of high thermal conductivity fillers in the composite material is conducive to the formation of a thermal network, thereby significantly improving the thermal conductivity of the material, but at the same time this method will also affect the mechanical properties of the composite material. It leads to serious problems such as a serious decline in the machinability of materials; as we all know, the key to improving the thermal conductivity of composite materials is to form a heat conduction chain or network parallel to the direction of heat flow in the system. Related studies have found that under the condition of an external magnetic field, the magnetic The filler can form many chains along the direction of the magnetic field under the action of the external magnetic field, and the direction of the chain arrangement is consistent with the magnetic field; the commonly used thermal conductive fillers are mostly ceramic fillers, metal oxides, metal nitrides or carbides. However, these Fillers, especially when added in a low amount, are difficult to form a heat-conducting network chain. The developed heat-conducting rubber generally has the defect of low thermal conductivity. Although silicone rubber, as a special synthetic rubber, exhibits excellent physical and chemical properties, it is the same Like most polymer materials, thermal conductivity is very low.

Chinese patent 201210528511.1 discloses a method for preparing a micro-nano hybrid filler liquid silicone rubber heat-conducting composite material. In the patent, micron-sized heat-conducting particles and nano-fibrous heat-conducting fillers are respectively added to the silicone rubber matrix, and the nanometer Fibrous fillers are oriented as connecting lines, thus forming thermal chains; as we all know, the dispersion of nanofillers has always been the central problem of polymer-based nanocomposites, and it is also the bottleneck restricting the performance of composite materials. The fibrous nanofillers added in the patent are relatively For nanoparticles, the dispersion problem is more prominent, but the patent does not solve the dispersion problem of nanofibrous fillers.

In response to the above problems, this patent disperses and composites magnetic nano-metal particles on the surface of micron-scale thermally conductive fillers to prepare magnetic composite thermally conductive fillers, and uses micro-nano composites to bring magnetic responsiveness. The arrangement and orientation of the composite fillers can be adjusted to realize the directional arrangement of the composite thermally conductive fillers in the silicone rubber matrix, and then realize the preparation of high thermally conductive silicone rubber composites with anisotropic thermal conductivity at a low filling fraction of the fillers. In addition, through magnetic nano-metal Micro-nano composite fillers are prepared by coating thermally conductive fillers with particles, which can avoid the difficulty of dispersion and agglomeration of nano-metal particles in the polymer matrix, and can indirectly realize the uniform dispersion of micro-nano particles in the polymer matrix.

Contents of the invention

The purpose of the present invention is to provide a method for preparing a two-component liquid silicone rubber composite material filled with magnetic micro-nano composite fillers with high thermal conductivity and excellent comprehensive performance for the shortcomings of the existing filled heat-conducting silicone rubber and its preparation method.

The specific steps of the preparation method of the present invention are as follows:

Step 1: Preparation of magnetic nanoparticle/microparticle composite thermally conductive filler:

Taking micron-sized particles and soluble metal salts as starting materials, weighing a certain number of soluble metal salts, adding ethylene glycol to dissolve; adding a certain number of parts by mass of micron-sized particles to the above solution under stirring conditions, Continue to stir to disperse the micron-sized particles evenly; add the prepared sodium hydroxide solution, and continue to stir until the metal ion hydroxide is fully formed; use the above sodium hydroxide solution to adjust the pH value of the solution to 10; finally add the reducing agent to carry out Reduction, that is, the ethylene glycol solution of the magnetic nanoparticle/microparticle composite thermally conductive filler; after filtering, washing and drying, the composite thermally conductive filler is obtained.

Step 2: After drying the composite thermally conductive filler obtained in step 1, weigh a certain amount of composite thermally conductive filler and add it to component A of the two-component liquid silicone rubber, and stir until uniform.

Step 3: Add an appropriate amount of component B of the two-component liquid silicone rubber to the mixture obtained in step 2, and stir quickly to make it evenly mixed.

Step 4: Inject the mixed liquid obtained in Step 3 into a mold with a magnetic field applied thereto and solidify at room temperature, and dry to prepare a magnetic micro-nano composite filler/silicone rubber heat-conducting composite material.

In step 1, the micron-sized particles are one of aluminum oxide, zinc oxide, magnesium oxide, silicon nitride, aluminum nitride, boron nitride and silicon carbide, and the particle size of the particles is 1-50 μm; The soluble metal salt is selected from one or more of chlorate, nitrate, acetate, sulfate and oxalate of iron, nickel or cobalt; the reducing agent is hydrazine hydrate or sodium borohydride A kind of; the generated magnetic nano-particles are the mixed particles of one or more kinds of nano-metal particles iron, nickel and cobalt, and the nano-sized particles account for 1% to 10% of the mass fraction of the composite thermally conductive filler.

In step 2, the stirring time is 10~24h.

In step 4, the magnetic field strength is 0.1-2.5T.

In step 4, the curing time is 10~20h.

The magnetic nanoparticle/microparticle composite heat-conducting filler accounts for 5% to 50% of the total mass of the magnetic micro-nano composite filler/silicone rubber heat-conducting composite material.

The silicone rubber is a commercially available two-component, room-temperature-curing liquid silicone rubber, wherein, the A component is a viscous silicone rubber fluid that is not cross-linked and vulcanized, and the B component is composed of a vulcanizing agent, a cross-linking agent and A liquid mixture composed of a tackifier; the amount of component B added accounts for 5% to 15% of the total mass of liquid silicone rubber.

Disperse and compound magnetic nano-metal particles on the surface of micron-scale thermally conductive fillers, and apply a magnetic field during the preparation of thermally conductive silicone rubber composites, so that the micron-scale thermally conductive fillers that do not have a magnetic field response are aligned in the polymer matrix to achieve low filling The thermal conductivity of the polymer-based composite material is greatly improved when the content is low; in addition, the micro-nano composite filler is prepared by coating the thermally conductive filler with magnetic nano-metal particles, which can avoid the problem that the nano-metal particles are not easy to disperse and agglomerate in the polymer matrix, and can be indirectly realized. Uniform dispersion of micro-nanoparticles in a polymer matrix.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings that need to be used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the following descriptions related to the present invention The accompanying drawings are only some embodiments of the present invention, and those skilled in the art can obtain other drawings according to these drawings without any creative effort.

Fig. 1 is a schematic diagram of the preparation process of the magnetic micro-nano composite filler/silicone rubber heat-conducting composite material in the present invention, as shown in the figure, the magnetic nano-metal particles are dispersed and compounded on the surface of the micron-scale heat-conducting filler, during the preparation process of the heat-conducting silicone rubber composite material A magnetic field is applied to align the micron-sized thermally conductive fillers that do not have a magnetic field response in the polymer matrix, so that the filler can greatly improve the thermal conductivity of the polymer matrix composite at a low filling content.

Fig. 2 is the scanning electron microscope picture of the magnetic nano-scale metallic nickel particle/micron-sized aluminum oxide heat-conducting composite filler prepared in the embodiment 1 of the present invention, as can be seen from the figure that the nano-sized metallic nickel particle is uniformly dispersed in the surface of the alumina particle surface, forming a nano-layer on the surface of alumina.

Fig. 3 is an XRD pattern of the micron-sized alumina filler used in the embodiment of the present invention, the prepared nano-sized metallic nickel particles and the metallic nickel particle/alumina composite filler.

Detailed ways

The invention will be described below with reference to its implementation.

Example 1:

Weigh 1.18g (5mmol) of nickel chloride hexahydrate (NiCl ₂ 6H ₂ O), add 50ml of ethylene glycol under stirring conditions until completely dissolved; weigh 2.5g of alumina micro-particles with an average particle size of 3μm , added to the ethylene glycol solution of nickel chloride, and continued to stir to disperse the alumina particles evenly; during the stirring process, dropwise added sodium hydroxide solution until nickel hydroxide was fully formed; adjusted the pH value of the solution to 10 to generate nickel hydroxide /alumina composite particles, continue to stir for 30min; add the aqueous solution of hydrazine hydrate dropwise until the reaction is complete, then separate the reaction mixture solution, wash 5 times with deionized water, and dry at 80°C for 10 hours to obtain 2.74g of Nano-nickel/alumina composite thermally conductive filler, wherein the mass fraction of nano-nickel particles in the composite thermally conductive filler is 9%.

Weigh 1g of the composite thermally conductive filler prepared above, add it to 8.1g of component A of two-component liquid silicone rubber and stir for 12 hours to make it evenly mixed; add 0.9g of component B of two-component liquid silicone rubber to the above mixed solution Components, stir quickly to make them evenly mixed, and the mass fraction of the composite heat-conducting filler in the heat-conducting composite material is 10%.

Inject the mixed solution into a mold with a 0.5T magnetic field and cure it at room temperature for 12 hours. After drying, a silicone rubber thermally conductive composite material is obtained. Use a thermal conductivity tester to test the thermal conductivity of pure silicone rubber and sample 1, and the test temperature is room temperature; The measured thermal conductivity of the pure silicone rubber sample is 0.19 W/(m.k), and the thermal conductivity of the sample in this embodiment is 0.28 W/(m.k).

Fig. 2 is a scanning electron micrograph of the nano-nickel/alumina composite filler prepared for this example. It can be seen from the figure that nano-scale metallic nickel particles are uniformly dispersed on the surface of the alumina particles, forming a nano-layer on the surface of the alumina.

Figure 3 is the X-ray diffraction pattern of this sample and pure nano-nickel particles and pure alumina particles, as can be seen from the figure, compared with pure nano-nickel particles and pure alumina particles, the spectrogram of the composite filler can be indexed as The phase of nickel and alumina, without the existence of other impurity phases.

Example 2:

Weigh 2.11g (5mmol) of ferric nitrate nonahydrate (Fe(NO ₃ ) ₃ 9H ₂ O), add 50ml of ethylene glycol under stirring conditions until completely dissolved; weigh 4.5g of nitrogen with an average particle size of 1μm Add boron nitride microparticles into the ethylene glycol solution of ferric nitrate, and continue stirring to disperse the boron nitride particles evenly; add sodium hydroxide solution dropwise during stirring until ferric hydroxide is fully formed; adjust the pH value of the solution to 10, Ferric hydroxide/boron nitride composite particles were generated, and the stirring was continued for 30 min; an aqueous solution of sodium borohydride was added dropwise until the reaction was complete. Then the reaction mixture solution was separated, washed 5 times with deionized water, and dried at 80°C for 10 hours to obtain 4.73g of nano-iron/boron nitride composite filler, wherein the mass fraction of nano-iron particles in the composite thermally conductive filler was 5%. .

Weigh 2g of the composite thermally conductive filler prepared above, add it to 7.2g of component A of two-component liquid silicone rubber and stir for 12 hours to make it evenly mixed; add 0.8g of component B of two-component liquid silicone rubber to the above mixed solution Components, stir quickly to make them evenly mixed, and the mass fraction of the composite heat-conducting filler in the heat-conducting composite material is 20%.

The mixed solution was injected into a mold with a 1T magnetic field and cured at room temperature for 14 hours. After drying, a silicone rubber thermally conductive composite material was obtained. The thermal conductivity of sample 2 was tested with a thermal conductivity tester. The test temperature was room temperature. The thermal conductivity of the sample is 0.37 W/(m.k).

The scanning electron microscope photo of the nano-iron/boron nitride composite filler is similar to that in Figure 2. The nano-scale metallic iron particles are uniformly dispersed on the surface of the boron nitride particles, forming a nano-layer on the surface of the boron nitride.

Example 3:

Weigh 1.3g (5mmol) of nickel sulfate hexahydrate (NiSO ₄ 6H ₂ O), add 50ml of ethylene glycol under stirring conditions until completely dissolved; weigh 4g of aluminum nitride micro-particles with an average particle size of 20μm, Add it into the ethylene glycol solution of nickel sulfate, and continue to stir to disperse the alumina particles evenly; add sodium hydroxide solution dropwise during the stirring process until nickel hydroxide is fully formed; adjust the pH value of the solution to 10, and generate nickel hydroxide/nitrogen Aluminum composite particles, continue to stir for 30min; add sodium borohydride aqueous solution dropwise until the reaction is complete. Then the reaction mixture solution was separated, washed 5 times with deionized water, and dried at 80°C for 10 hours to obtain 4.23g of nano-nickel/aluminum nitride composite filler, wherein the mass fraction of nano-nickel particles in the composite thermally conductive filler was 5%. .

Weigh 1g of the above-prepared composite filler, add it to 8.1g of component A of two-component liquid silicone rubber and stir for 12 hours to make it evenly mixed; add 0.9g of component B of two-component liquid silicone rubber to the above mixture parts, stir quickly to make it evenly mixed, and the mass fraction of the composite filler in the heat-conducting composite material is 10%.

The mixed solution was injected into a mold with a 0.5T magnetic field applied to it and cured at room temperature for 14 hours. After drying, a silicone rubber thermally conductive composite material was obtained. The thermal conductivity of sample 3 was tested with a thermal conductivity tester. The test temperature was room temperature. The thermal conductivity of the medium sample is 0.25 W/(m.k).

The scanning electron microscope photo of the nano-nickel/aluminum nitride composite filler is similar to that shown in Figure 2. Nano-scale metallic nickel particles are uniformly dispersed on the surface of the aluminum nitride particles, forming a nano-layer on the surface of the aluminum nitride.

Example 4:

Weigh 1.25g (5mmol) of cobalt acetate tetrahydrate (Co·C ₄ H ₆ O ₄ 4H ₂ O), add 50ml of ethylene glycol under stirring conditions until completely dissolved; weigh 3.5g with an average particle size of 3μm Add silicon carbide micron particles into the ethylene glycol solution of cobalt acetate, continue to stir to disperse the silicon carbide particles evenly; add dropwise sodium hydroxide solution until the cobalt hydroxide is fully formed during stirring; adjust the pH value of the solution to 10, Generate cobalt hydroxide/silicon carbide composite particles, continue to stir for 30 minutes; add the aqueous solution of hydrazine hydrate dropwise until the reaction is complete, then separate the reaction mixture solution, wash with deionized water 5 times, and dry at 80°C for 10 hours 3.74g of nano-cobalt/silicon carbide composite filler was obtained, wherein the mass fraction of nano-cobalt particles in the composite thermally conductive filler was 6%.

Weigh 3g of the above-prepared composite filler, add it to 6.3g of component A of two-component liquid silicone rubber and stir for 12 hours to make it evenly mixed; add 0.7g of component B of two-component liquid silicone rubber to the above mixture parts, stir quickly to make it evenly mixed, and the mass fraction of the composite filler in the heat-conducting composite material is 30%.

The mixed solution was injected into a mold with a 1.5T magnetic field and cured at room temperature for 14 hours. After drying, a silicone rubber thermally conductive composite material was obtained. The thermal conductivity of sample 4 was tested with a thermal conductivity tester. The thermal conductivity of the medium sample is 0.42 W/(m.k).

The scanning electron microscope photo of the nano-cobalt/silicon carbide composite filler is similar to that in Figure 2. Nano-scale metal cobalt particles are uniformly dispersed on the surface of the silicon carbide particles, forming a nano-layer on the surface of the silicon carbide.

Claims (7)

1. The preparation method of magnetic micro-nano composite filler/silicone rubber heat-conducting composite material is characterized in that the specific steps are as follows: Step 1: Preparation of Magnetic Nanoparticle/Microparticle Composite Thermally Conductive Filler Taking micron-sized particles and soluble metal salts as starting materials, weighing a certain number of soluble metal salts, adding ethylene glycol to dissolve; adding a certain number of parts by mass of micron-sized particles to the above solution under stirring conditions, Continue to stir to disperse the micron-sized particles evenly; add the prepared sodium hydroxide solution, and continue to stir until the metal ion hydroxide is fully formed; use the above sodium hydroxide solution to adjust the pH value of the solution to 10; finally add the reducing agent to carry out Reduction, that is, the ethylene glycol solution of the magnetic nanoparticle/microparticle composite thermally conductive filler; after filtering, washing and drying, the composite thermally conductive filler is obtained; Step 2: After drying the composite thermally conductive filler obtained in step 1, weigh a certain mass of composite thermally conductive filler and add it to component A of the two-component liquid silicone rubber, and stir until uniform; Step 3: Add an appropriate amount of component B of the two-component liquid silicone rubber to the mixture obtained in step 2, and stir quickly to make it evenly mixed; Step 4: Inject the mixed liquid obtained in Step 3 into a mold with a magnetic field applied thereto and solidify at room temperature, and dry to prepare a magnetic micro-nano composite filler/silicone rubber heat-conducting composite material. 2. The preparation method of magnetic micro-nano composite filler/silicone rubber heat-conducting composite material as claimed in claim 1, characterized in that: in step 1, the micron-sized particles are aluminum oxide, zinc oxide, magnesium oxide, nitride One of silicon, aluminum nitride, boron nitride and silicon carbide, the particle size of the particles is 1-50 μm; the soluble metal salt is selected from iron, nickel or cobalt chlorate, nitrate, acetate One or more of , sulfate and oxalate; the reducing agent is one of hydrazine hydrate or sodium borohydride; the magnetic nano-scale particles generated are one of nano-metal particles iron, nickel and cobalt Or more than two kinds of mixed particles, nano-sized particles account for 1% to 10% of the mass fraction of the composite thermally conductive filler. 3. The method for preparing magnetic micro-nano composite filler/silicone rubber heat-conducting composite material according to claim 1, characterized in that: in step 2, the stirring time is 10-24 hours. 4 . The method for preparing magnetic micro-nano composite filler/silicone rubber heat-conducting composite material according to claim 1 , characterized in that: in step 4, the magnetic field strength is 0.1-2.5T. 5. The method for preparing magnetic micro-nano composite filler/silicone rubber heat-conducting composite material according to claim 1, characterized in that: in step 4, the curing time is 10-20 hours. 6. The preparation method of magnetic micro-nano composite filler/silicone rubber heat-conducting composite material as claimed in claim 1, characterized in that: the magnetic nano-particle/micron-particle composite heat-conducting filler accounts for 5%~50% of the total mass of composite materials. 7. The preparation method of magnetic micro-nano composite filler/silicone rubber heat-conducting composite material as claimed in claim 1, characterized in that: said silicone rubber is a commercially available two-component, room-temperature-curing liquid silicone rubber, wherein, Component A is uncrosslinked and vulcanized viscous silicone rubber fluid, and component B is a liquid mixture composed of vulcanizing agent, crosslinking agent and tackifier; the amount of component B added accounts for the total amount of liquid silicone rubber. 5%~15% of the mass.