Composite filler containing silicon oxide micropowder and preparation method thereof

Abstract

The invention provides a composite filler containing silicon oxide micro powder and a preparation method thereof, and belongs to the technical field of heat conduction material filling. The preparation process comprises the following steps: modifying the silicon oxide micro powder; preparing composite hybrid particles; modifying the composite hybrid particles; and preparing the composite filler. The polyquaternium-7 and the lauryl sodium sulfate cooperate to modify the silicon oxide micro powder, agglomeration is hindered, a heat conduction path is formed, the interfacial interaction with resin is enhanced, and the viscosity is low under high solid content; aluminum oxide is treated at high temperature to form a dendritic structure, graphene oxide is adsorbed to construct a heat-conducting framework, and agglomeration is prevented through electrostatic-hydrogen-bond interaction; meanwhile, p-phenylenediamine and ascorbic acid are used for double modification of composite particles, polarity is enhanced, graphene oxide is reduced, electrostatic repulsion and steric hindrance are synergistically dispersed, and therefore the prepared composite filler solves the multiple problems of dispersion stability, interface compatibility, heat-conducting network construction, processing fluidity under high filling and the like at the same time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat-conducting material filling, in particular to a composite filler containing silicon oxide powder and a preparation method thereof. BACKGROUND

[0002] With the development of electronic and electrical equipment towards miniaturization, integration and high performance, the thermal conductivity of epoxy resin-based composites as key materials in the fields of electronic packaging, heat dissipation components and the like has become a key factor restricting the performance improvement of products. Adding heat-conductive fillers to the epoxy resin matrix is the main means to improve the thermal conductivity of the composite material, but traditional fillers face many problems in practical application.

[0003] The fillers represented by silicon oxide powder are prone to agglomeration through hydrogen bonding due to the presence of a large number of silicon hydroxyl groups on their surfaces, which not only seriously affects the dispersion uniformity in the epoxy resin, but also forms a thermal resistance interface, hindering heat conduction, resulting in difficulty in improving the thermal conductivity of the composite material. At the same time, under high filler content, the agglomerated fillers can greatly increase the viscosity of the system, greatly reducing the processing fluidity of the material.

[0004] Although there have been studies to improve the performance of fillers through surface modification and the like, most of them only improve single defects of a single filler, and it is difficult to solve multiple problems such as dispersion stability, interface compatibility, thermal conductivity network construction and processing fluidity under high filling at the same time.

[0005] Therefore, it is urgent to develop an innovative composite filler containing silicon oxide powder and a preparation method thereof to significantly improve the thermal conductivity of epoxy resin-based composites, while overcoming the drawbacks of traditional fillers at high filling. SUMMARY

[0006] In view of the deficiencies of the prior art, the purpose of the present application is to provide a composite filler containing silicon oxide powder and a preparation method thereof.

[0007] A composite filler containing silicon oxide powder, consisting of: modified silicon oxide powder and double-modified composite hybrid particles; The modified silicon oxide powder is specifically obtained by adding polyquaternary ammonium salt-7 and sodium dodecyl sulfate to a silicon oxide powder slurry with a pH of 9.5-10.5, stirring to obtain a mixed slurry, and reacting the mixed slurry at 85-90℃ to obtain the modified silicon oxide powder, the addition amount of polyquaternary ammonium salt-7 being 0.2-0.3wt% of the mixed slurry, and the addition amount of sodium dodecyl sulfate being 0.3-0.5wt% of the mixed slurry; The double modification modified composite hybrid particles are prepared by adding p-phenylenediamine into the water dispersion of the composite hybrid particles to adjust the pH to 11, modifying at 90-92°C, and then adding ascorbic acid into the water dispersion of the p-phenylenediamine modified composite hybrid particles to modify at 80-82°C. The composite hybrid particles are prepared by calcining nanospherical alumina to prepare dendritic alumina, modifying the dendritic alumina with a silane coupling agent, and then mixing the modified dendritic alumina with a 2-3 mg / mL aqueous solution of graphene oxide, the weight ratio of the aqueous solution of graphene oxide to the modified dendritic alumina being 5-6:2-3.

[0008] A method for preparing a composite filler containing silica powder, comprising the following steps: S1: modification treatment of the silica powder The silica powder is added into deionized water, the pH is adjusted, polyquaternary ammonium salt-7 is added, and then sodium dodecyl sulfate is added after the reaction, and the modified silica powder is obtained after further reaction; S2: preparation of the composite hybrid particles Nanospherical alumina is calcined to prepare dendritic alumina, the dendritic alumina is modified with a silane coupling agent, the modified dendritic alumina is mixed with an aqueous solution of graphene oxide, and the composite hybrid particles are prepared after dispersion and stirring; S3: modification of the composite hybrid particles The composite hybrid particles are dispersed in deionized water, p-phenylenediamine is added, and ammonia water is added to adjust the pH, and then the p-phenylenediamine modified composite hybrid particles are obtained after centrifugation, washing, and drying. The p-phenylenediamine modified composite hybrid particles are further modified with ascorbic acid to obtain the double modification modified composite hybrid particles; S4: preparation of the composite filler The modified silica powder and the double modification modified composite hybrid particles are mixed and ball milled at a mass ratio of 10-12:8-10 to obtain the composite filler.

[0009] Further, the modification treatment of the silica powder in step S1 comprises the following steps: S1.1: 100-120 parts by weight of the silica powder are added into 100-120 parts by weight of deionized water, and then stirred at 300-500 rpm for 20-30 min. Sodium hydroxide solution is added to adjust the pH to 9.5-10.5, and then the mixture is continuously stirred for 20-30 min to obtain a slurry; S1.2: Sodium dodecyl sulfate is added to the slurry, and the mixture is stirred at 300-500 rpm for 20-30 min. Then, polyquaternary ammonium salt-7 is added, and the mixture is stirred at 300-500 rpm for 20-30 min to obtain a mixed slurry. The mixed slurry is stirred at 85-90°C and 300-500 rpm for 4-5 h, followed by centrifugation. The centrifugation precipitate is washed and dried, and then ground for 20-30 min to obtain modified silica micro powder.

[0010] Further, the preparation of the composite hybrid particles in step S2 specifically includes the following steps: S2.1: The nanometer spherical alumina is sieved through a 100-120 mesh sieve, and then dried at 60-80°C for 24-25 h. Then, it is placed in a muffle furnace and incubated at 1250-1300°C for 4.5-5 h at a heating rate of 5-6°C / min, and then naturally cooled to room temperature to obtain dendritic alumina; S2.2: 5-8 parts by weight of dendritic alumina is added to 90-100 parts by weight of 95wt% ethanol aqueous solution, and then ultrasonically dispersed for 20-30 min. Then, 0.5-0.8 parts by weight of silane coupling agent KH550 is added, and 2-3 parts by weight of formic acid is added. The mixture is stirred at 100-150 rpm in a reflux device at 90-92°C for 24-25 h. After the reaction is completed, the mixture is cooled, filtered, washed, and dried to obtain modified dendritic alumina; S2.3: 50-60 parts by weight of 2-3 mg / mL graphene oxide aqueous solution is added to 500-550 parts by weight of deionized water, and ultrasonically dispersed for 10-20 min. Then, 20-30 parts by weight of modified dendritic alumina is added, and the mixture is stirred at 200-300 rpm for 90-100 min. After stirring is completed, the mixture is centrifuged and dried to obtain composite hybrid particles.

[0011] Further, the modification of the composite hybrid particles in step S3 specifically includes the following steps: S3.1: 20-30 parts by weight of the composite hybrid particles is added to 250-280 parts by weight of deionized water, and then dispersed for 60-70 min. Then, p-phenylenediamine is added, and the amount of p-phenylenediamine is 3-5wt% of the composite hybrid particles. Ammonia is added to adjust the pH to 11. Then, the mixture is stirred at 90-92°C for 3-4 h. After that, the mixture is centrifuged, washed, and dried to obtain p-phenylenediamine modified composite hybrid particles; S3.2: The p-phenylenediamine modified composite hybrid particles are added to 100-120 parts by weight of deionized water, and dispersed for 20-30 min. Then, 3-5 parts by weight of ascorbic acid is added. The mixture is stirred in a water bath at 80-82°C, and condensation reflux is performed. The reaction is carried out for 8-10 h. Then, the mixture is suction filtered, washed, and freeze-dried to obtain double modified composite hybrid particles.

[0012] Further, the preparation of the composite filler in step S4 specifically comprises the following steps: The modified silica powder and the double-modified composite hybrid particles are mixed in a mass ratio of 10-12:8-10, and then placed in a planetary ball mill, followed by adding zirconia balls and ball milling for 30-40 min to obtain the composite filler.

[0013] Further, the amount of p-phenylenediamine added in step S3.1 is 3-5 wt% of the composite hybrid particles.

[0014] Further, the ball-to-material volume ratio in step S4 is 3-5:1.

[0015] Compared with the prior art, the present application has at least the following beneficial effects: 1. In the present application, the silica powder is modified by polyquaternary ammonium salt-7 and sodium dodecyl sulfate. After modification, the silica powder occupies the hydrogen bond sites of silicon hydroxyl by sodium dodecyl sulfate, preventing the agglomeration of particles through hydrogen bonds formed by silicon hydroxyl. At the same time, the steric hindrance effect of polyquaternary ammonium salt-7 further prevents particle aggregation. Uniformly dispersed silica powder forms a more dense "heat conduction path" in the epoxy resin, reduces the thermal resistance interface caused by agglomeration, and improves the efficiency of heat conduction through the filler particles. Polyquaternary ammonium salt-7 can form strong interactions with polar groups in the epoxy resin, reducing the voids and defects at the filler-resin interface, thereby improving the overall thermal conductivity of the composite material. The dispersion stability of the modified silica powder is improved, and it has the characteristics of high solid content and low viscosity. A higher proportion of filler can be added to the epoxy resin without affecting the processing fluidity, significantly improving the thermal conductivity.

[0016] 2. In the present application, the nanometer spherical alumina is converted into a dendritic structure through high-temperature treatment, and the specific surface area is increased. The "branches" of the dendritic structure can form a three-dimensional interpenetrating network, which is more easily constructed into a continuous "heat conduction skeleton" in the composite material, improving the thermal conductivity of the epoxy resin. The modified dendritic alumina adsorbs graphene oxide on its surface, and the composite hybrid particles formed can fill the thermal resistance interface between the alumina branches through the in-plane thermal conductivity of graphene oxide, thereby effectively improving the thermal conductivity. The carboxyl and hydroxyl groups on the surface of the graphene oxide form an electrostatic-hydrogen bond double action with the amino groups on the surface of the modified alumina, preventing particle agglomeration and maintaining a single dispersed state at a filling amount, thereby avoiding the problem of rapid increase in viscosity when traditional fillers are highly filled.

[0017] 3、The application is modified by p-phenylenediamine and ascorbic acid, the p-phenylenediamine modification makes the particle surface polarity enhanced, the chemical compatibility with the polar matrix such as epoxy resin is improved, the void and defect of the filler-resin interface is reduced, the interface thermal resistance is reduced, the ascorbic acid has reducibility, which can reduce the oxygen-containing groups on the surface of graphene oxide, restore the conjugated structure, and improve the intrinsic thermal conductivity of graphene oxide, and after the p-phenylenediamine modification, the particle surface is positively charged due to the protonation of the amino group, and the particle agglomeration is inhibited by electrostatic repulsion; the ascorbic acid modification further introduces hydroxyl groups to form a steric hindrance effect, and the dispersion uniformity is improved under the dual action, after the dual modification, the surface defects of the composite hybrid particles are reduced, the interface thermal resistance is reduced, and a higher proportion can be added in the epoxy resin to form a dense thermal conduction network, thereby improving the overall thermal conductivity.

[0018] 4、The composite filler prepared by mixing the composite hybrid particles with the modified silica powder and ball milling is added to the epoxy resin, the silica powder fills the voids, the composite hybrid particles construct a high thermal conductivity skeleton, a three-dimensional thermal conduction network combined by "point-line-plane" can be formed, and the surfaces of the two are both polar modified, the interface bonding force with the epoxy resin is consistent, the compatibility of the composite hybrid particles and the silica powder with the epoxy resin can be improved, the problem of inconsistent thermal resistance caused by the difference in interface properties can be avoided, thereby the thermal conductivity of the epoxy resin material can be significantly improved, and the problem of rapid increase in viscosity caused by high filling of the traditional filler can be avoided. BRIEF DESCRIPTION OF DRAWINGS

[0019] The accompanying drawings, which are incorporated herein and constitute part of the specification, illustrate embodiments of the application and, together with the description, further serve to explain the principles of the application and to enable a person skilled in the relevant art to implement and use the application.

[0020] Figure 1 A preparation method flowchart of a composite filler containing silica powder for the embodiments of the application; Figure 2 An SEM image of the dendritic aluminum oxide of embodiment 1 of the application. DETAILED DESCRIPTION

[0021] The composite filler containing silica powder and the preparation method thereof provided by the application will be described in detail below in combination with the drawings and specific embodiments. It should be noted that, in order to make the embodiments more detailed, the following embodiments are the best and preferred embodiments, and other alternative ways can also be used by those skilled in the art to implement them; and the drawings are only used to more specifically describe the embodiments, and are not intended to specifically limit the application.

[0022] Embodiment 1 A method for preparing a composite filler containing silica micropowder, such as... Figure 1 As shown, it includes the following steps: S1: Modification treatment of silica micro powder S1.1: Add 100 parts by weight of silica micro powder to 100 parts by weight of deionized water, then stir at 300 rpm for 20 min, then add sodium hydroxide solution to adjust the pH to 9.5, and then continue stirring and mixing for 20 min to obtain a slurry; S1.2: Add sodium dodecyl sulfate to the slurry and stir at 300 rpm for 20 min. Then add polyquaternium-7 and stir at 300 rpm for 20 min to obtain a mixed slurry. Stir the mixed slurry at 85℃ and 300 rpm for 4 h. Then centrifuge, wash and dry the centrifuged precipitate, and then grind it for 20 min to obtain the modified silica micro powder. The amount of polyquaternium-7 added is 0.2 wt% of the mixed slurry, and the amount of sodium dodecyl sulfate added is 0.3 wt% of the mixed slurry; S2: Preparation of composite hybrid particles S2.1: The nano-spherical alumina was passed through a 100-mesh sieve, dried at 60℃ for 24h, then placed in a muffle furnace and held at 1250℃ for 4.5h at a heating rate of 5℃ / min, and then naturally cooled to room temperature to obtain branched alumina. S2.2: 5 parts by weight of branched alumina were added to 90 parts by weight of 95 wt% ethanol aqueous solution, and then ultrasonically dispersed for 20 min. Then, 0.5 parts by weight of silane coupling agent KH550 and 2 parts by weight of formic acid were added. The mixture was stirred at 100 rpm for 24 h in a reflux apparatus at 90 °C. After the reaction was completed, the mixture was cooled, filtered, washed, and dried to obtain modified branched alumina. S2.3: Add 50 parts by weight of 2 mg / mL graphene oxide aqueous solution to 500 parts by weight of deionized water, ultrasonically disperse for 10 min, then add 20 parts by weight of modified branched alumina, stir and mix at 200 rpm for 90 min, centrifuge and dry after stirring to obtain composite hybrid particles. S3: Modification of composite hybrid particles S3.1: Add 20 parts by weight of the composite hybrid particles to 250 parts by weight of deionized water, disperse for 60 min, then add p-phenylenediamine at 3 wt% of the composite hybrid particles, and add ammonia to adjust the pH to 11. Then stir the reaction at 90 °C for 3 h, then centrifuge, wash and dry to obtain p-phenylenediamine modified composite hybrid particles. S3.2: The above p-phenylenediamine modified composite hybrid particles were added to 100 parts by weight of deionized water, dispersed for 20 min, then 3 parts by weight of ascorbic acid was added, then stirred under 80°C water bath and condensed reflux, reacted for 8h, then filtered, washed, freeze-dried to obtain double modified composite hybrid particles; S4: Preparation of composite filler The modified silica powder and the double modified composite hybrid particles were mixed in a mass ratio of 10:8, then placed in a planetary ball mill, then added zirconium oxide balls, the ball-to-material volume ratio was 3:1, ball milling for 30 min to obtain the composite filler.

[0023] Example 2 A preparation method of a composite filler containing silica powder, as shown in Figure 1 , comprising the following steps: S1: Modification treatment of silica powder S1.1: 120 parts by weight of silica powder was added to 120 parts by weight of deionized water, then stirred at 300 rpm for 20 min, then sodium hydroxide solution was added to adjust the pH to 10.5, then continue to stir and mix for 20 min to obtain the slurry; S1.2: Sodium dodecyl sulfate was added to the slurry, stirred and mixed at 300 rpm for 20 min, then polyquaternary ammonium salt-7 was added, stirred and mixed at 300 rpm for 20 min to obtain the mixed slurry, then the mixed slurry was stirred and mixed at 85°C and 300 rpm for 4h, then centrifuged, the centrifugal precipitate was washed and dried, then ground for 20 min to obtain the modified silica powder; The addition amount of polyquaternary ammonium salt-7 was 0.3wt% of the mixed slurry, and the addition amount of sodium dodecyl sulfate was 0.5wt% of the mixed slurry; S2: Preparation of composite hybrid particles S2.1: The nanometer spherical alumina was passed through a 100 mesh sieve, then dried at 60°C for 24h, then placed in a muffle furnace, heated at 1250°C for 4.5h, the heating rate was 5°C / min, then naturally cooled to room temperature to obtain the dendritic alumina; S2.2: 8 parts by weight of dendritic alumina was added to 100 parts by weight of 95wt% ethanol aqueous solution, then ultrasonic dispersed for 20 min, then 0.8 parts by weight of silane coupling agent KH550 was added, and 3 parts by weight of formic acid was added, then stirred at 100 rpm in a reflux device at 90°C for 24h, after the reaction was completed, cooled, filtered, washed, dried to obtain the modified dendritic alumina; S2.3: 60 parts by weight of 3 mg / mL graphene oxide aqueous solution was added to 550 parts by weight of deionized water, ultrasonic dispersion was carried out for 10 min, then 30 parts by weight of modified dendritic aluminum oxide was added, the mixture was stirred at 200 rpm for 90 min, after stirring was completed, centrifugation was carried out, drying was carried out, and the composite hybrid particles were obtained; S3: Modification of the composite hybrid particles S3.1: 30 parts by weight of the composite hybrid particles was added to 280 parts by weight of deionized water, then dispersed for 60 min, then p-phenylenediamine was added, the addition amount of p-phenylenediamine was 5 wt% of the composite hybrid particles, and ammonia water was added to adjust the pH to 11, then the stirring reaction was carried out at 90°C for 3 h, then centrifugation, washing, and drying were carried out, and the p-phenylenediamine modified composite hybrid particles were obtained; S3.2: The above p-phenylenediamine modified composite hybrid particles were added to 120 parts by weight of deionized water, dispersed for 20 min, then 5 parts by weight of ascorbic acid was added, then stirring was carried out in a water bath at 80°C, and condensation reflux was carried out, the reaction was carried out for 8 h, then filtration, washing, and freeze-drying were carried out, and the double modification modified composite hybrid particles were obtained; S4: Preparation of the composite filler The modified silicon oxide powder and the double modification modified composite hybrid particles were mixed in a mass ratio of 12:10, then zirconium oxide balls were added, the ball-to-material volume ratio was 5:1, ball milling was carried out for 30 min, and the composite filler was obtained.

[0024] Example 3 A preparation method of a composite filler containing silicon oxide powder, as shown in Figure 1 , comprises the following steps: S1: Modification treatment of the silicon oxide powder S1.1: 100 parts by weight of silicon oxide powder was added to 100 parts by weight of deionized water, then stirring was carried out at 500 rpm for 30 min, then sodium hydroxide solution was added to adjust the pH to 9.5, then stirring was continued for 30 min, and the slurry was obtained; S1.2: Sodium dodecyl sulfate was added to the slurry, stirring was carried out at 500 rpm for 30 min, then polyquaternary ammonium salt-7 was added, stirring was carried out at 500 rpm for 30 min, the mixed slurry was obtained, the mixed slurry was stirred at 90°C and 500 rpm for 5 h, then centrifugation was carried out, the centrifugation precipitate was washed and dried, then grinding was carried out for 30 min, and the modified silicon oxide powder was obtained; The addition amount of polyquaternary ammonium salt-7 was 0.2 wt% of the mixed slurry, and the addition amount of sodium dodecyl sulfate was 0.3 wt% of the mixed slurry; S2: Preparation of the composite hybrid particles S2.1: The nanometer spherical alumina is sieved through a 120 mesh sieve, then dried at 80℃ for 25h, then placed in a muffle furnace, incubated at 1300℃ for 5h, the heating rate is 6℃ / min, then naturally cooled to room temperature, to obtain dendritic alumina; S2.2: 5 parts by weight of dendritic alumina is added to 90 parts by weight of 95wt% ethanol aqueous solution, then ultrasonic dispersion for 30min, then 0.5 parts by weight of silane coupling agent KH550 is added, and 2 parts by weight of formic acid is added, and the reaction is carried out at 92℃ in a reflux device with stirring at 150rpm for 25h, after the reaction is completed, cooling, filtration, washing, drying, to obtain modified dendritic alumina; S2.3: 50 parts by weight of 2mg / mL graphene oxide aqueous solution is added to 500 parts by weight of deionized water, ultrasonic dispersion for 20min, then 20 parts by weight of modified dendritic alumina is added, and the mixture is stirred at 300rpm for 100min, after stirring is completed, centrifugation, drying, to obtain composite hybrid particles; S3: Modification of composite hybrid particles S3.1: 20 parts by weight of composite hybrid particles is added to 250 parts by weight of deionized water, then dispersed for 70min, then p-phenylenediamine is added, the amount of p-phenylenediamine added is 3wt% of the composite hybrid particles, and ammonia water is added to adjust the pH to 11, then stirred at 92℃ for 4h, then centrifuged, washed, dried, to obtain p-phenylenediamine modified composite hybrid particles; S3.2: The above p-phenylenediamine modified composite hybrid particles are added to 100 parts by weight of deionized water, dispersed for 30min, then 3 parts by weight of ascorbic acid is added, then stirred in a water bath at 82℃, and condensation reflux is carried out, the reaction is carried out for 10h, then suction filtration, washing, freeze-drying, to obtain double modified composite hybrid particles; S4: Preparation of composite filler The modified silica powder and the double modified composite hybrid particles are mixed in a mass ratio of 10:8, then placed in a planetary ball mill, then zirconia balls are added, the ball-to-material volume ratio is 3:1, ball milling for 40min, to obtain a composite filler.

[0025] Comparative Example 1 Comparative Example 1 is different from Example 1 in that it removes sodium dodecyl sulfate in step S1.2, and the rest of the steps remain unchanged to prepare a composite filler, which is denoted as Comparative Example 1.

[0026] Comparative Example 2 Comparative Example 2 is different from Example 1 in that it removes polyquaternary ammonium salt-7 in step S1.2, and the rest of the steps remain unchanged to prepare a composite filler, which is denoted as Comparative Example 2.

[0027] Comparative Example 3 Comparative Example 3 is different from Example 1 in that Comparative Example 3 is prepared by removing step S2.1, replacing the branched alumina in step S2.2 with spherical alumina, and the rest of the steps remain unchanged.

[0028] Comparative Example 4 Comparative Example 4 is different from Example 1 in that Comparative Example 4 is prepared by removing step S3.2, replacing the double-modified modified composite hybrid particles in step S4 with p-phenylenediamine modified composite hybrid particles, and the rest of the steps remain unchanged.

[0029] Comparative Example 5 Comparative Example 5 is different from Example 1 in that Comparative Example 5 is prepared by removing step S3, replacing the double-modified modified composite hybrid particles in step S4 with composite hybrid particles, and the rest of the steps remain unchanged.

[0030] Comparative Example 6 Comparative Example 6 is different from Example 1 in that Comparative Example 6 is prepared by removing step S1, replacing the modified silica powder in step S4 with silica powder, and the rest of the steps remain unchanged.

[0031] The composite fillers prepared in Examples 1-3 and Comparative Examples 1-6 are added to a bisphenol A type epoxy resin at a total filler content of 50wt%, after stirring and mixing uniformly, an acid anhydride curing agent is added, and a curing treatment is performed to obtain an epoxy resin composite material.

[0032] The thermal conductivity of the epoxy resin composite materials prepared in Examples 1-3 and Comparative Examples 1-5 is measured, and the results are shown in Table 1.

[0033] Table 1. Thermal conductivity measurement results of Examples 1-3 and Comparative Examples 1-5

[0034] As can be seen from the data in Table 1, the composite filler prepared by the present application can significantly improve the thermal conductivity of the epoxy resin composite material. As can be seen from the data of Comparative Examples 1-2, the thermal conductivity decreases compared to the examples, because the polyquaternary ammonium salt-7 and sodium dodecyl sulfate modified silica powder can not only improve the dispersibility of the composite filler, but also reduce the voids and defects at the interface between the composite filler and the resin, thereby improving the overall thermal conductivity of the composite material. As can be seen from the data of Comparative Example 3, branched alumina is more effective than spherical alumina in improving the thermal conductivity of the epoxy resin. As can be seen from the data of Comparative Examples 4-5, the overall thermal conductivity of the composite material can be significantly improved by double-modified modified composite hybrid particles with p-phenylenediamine and ascorbic acid.

[0035] The viscosity of the epoxy resin composites prepared in Examples 1-3 and Comparative Example 6 was measured at 30°C before curing, and the results are shown in Table 2.

[0036] Table 2. Viscosity measurement results of Examples 1-3 and Comparative Example 6

[0037] As can be seen from the data in Table 2, the composite filler prepared by this invention still has a low viscosity before curing even with a high filling amount of 50 wt%. This can reduce the viscosity of epoxy resin composite materials while effectively improving the thermal conductivity of the composite system. As can be seen from the data in Comparative Example 6, the synergistic modification of silica micropowder by polyquaternium-7 and sodium dodecyl sulfate can achieve high solid content and low viscosity characteristics, thereby solving the problem of sudden viscosity increase when traditional fillers are filled with high amounts.

[0038] from Figure 2 It can be seen that branched alumina can be prepared by high-temperature sintering.

[0039] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A composite filler containing silica micropowder, characterized in that, Composed of the following components Composition: Modified silica micro powder and dual-modified composite hybrid particles; The modified silica micropowder is specifically obtained by adding polyquaternium-7 and sodium dodecyl sulfate to a silica micropowder slurry with a pH of 9.5-10.5 and stirring to obtain a mixed slurry. The mixed slurry is then reacted at 85-90℃ to obtain the modified silica micropowder. The amount of polyquaternium-7 added is 0.2-0.3 wt% of the mixed slurry, and the amount of sodium dodecyl sulfate added is 0.3-0.5 wt% of the mixed slurry. The double-modified composite hybrid particles are specifically modified by adding p-phenylenediamine to the aqueous dispersion of the composite hybrid particles, adjusting the pH to 11, and performing modification treatment at 90-92℃. Then, ascorbic acid is added to the aqueous dispersion of the p-phenylenediamine-modified composite hybrid particles and modified at 80-82℃. The composite hybrid particles are prepared by high-temperature calcination to prepare branched alumina, which is then modified with a silane coupling agent and mixed with a 2-3 mg / mL aqueous solution of graphene oxide. The weight ratio of the aqueous solution of graphene oxide to the modified branched alumina is 5-6:2-3.

2. A method for preparing the composite filler containing silica micropowder as described in claim 1, characterized in that, Includes the following steps: S1: Modification treatment of silica micro powder Silica powder was added to deionized water, the pH was adjusted, polyquaternium-7 was added, sodium dodecyl sulfate was added after the reaction, and the reaction was continued to obtain modified silica powder. S2: Preparation of composite hybrid particles Branched alumina was prepared by calcining nano-spherical alumina, and then modified with a silane coupling agent. The modified branched alumina was then mixed, dispersed, and stirred with an aqueous solution of graphene oxide to prepare composite hybrid particles. S3: Modification of composite hybrid particles The composite hybrid particles were dispersed in deionized water, then p-phenylenediamine was added, and ammonia was added to adjust the pH. After the reaction, the particles were centrifuged, washed, and dried to obtain p-phenylenediamine-modified composite hybrid particles. The p-phenylenediamine-modified composite hybrid particles were then modified again with ascorbic acid to obtain double-modified composite hybrid particles. S4: Preparation of composite fillers The modified silica micro powder and the double-modified composite hybrid particles were mixed and ball-milled at a mass ratio of 10-12:8-10 to obtain the composite filler.

3. The method for preparing a composite filler containing silica micropowder according to claim 2, characterized in that, Step S1, the modification treatment of silica micro powder, specifically includes the following steps: S1.1: Add 100-120 parts by weight of silica micro powder to 100-120 parts by weight of deionized water, then stir at 300-500 rpm for 20-30 min, then add sodium hydroxide solution to adjust the pH to 9.5-10.5, and continue stirring and mixing for 20-30 min to obtain a slurry; S1.2: Add sodium dodecyl sulfate to the slurry and stir at 300-500 rpm for 20-30 min. Then add polyquaternium-7 and stir at 300-500 rpm for 20-30 min to obtain a mixed slurry. Stir the mixed slurry at 85-90℃ and 300-500 rpm for 4-5 h. Then centrifuge, wash and dry the centrifuged precipitate, and then grind it for 20-30 min to obtain modified silica micro powder.

4. The method for preparing a composite filler containing silica micropowder according to claim 3, characterized in that, The preparation of the composite hybrid particles in step S2 specifically includes the following steps: S2.1: The nano-spherical alumina is passed through a 100-120 mesh sieve, then dried at 60-80℃ for 24-25h, then placed in a muffle furnace and held at 1250-1300℃ for 4.5-5h at a heating rate of 5-6℃ / min, and then naturally cooled to room temperature to obtain branched alumina. S2.2: Add 5-8 parts by weight of branched alumina to 90-100 parts by weight of 95wt% ethanol aqueous solution, then ultrasonically disperse for 20-30 min, then add 0.5-0.8 parts by weight of silane coupling agent KH550 and 2-3 parts by weight of formic acid, and stir the reaction in a reflux device at 90-92℃ at 100-150 rpm for 24-25 h. After the reaction is completed, cool, filter, wash and dry to obtain modified branched alumina. S2.3: Add 50-60 parts by weight of 2-3 mg / mL graphene oxide aqueous solution to 500-550 parts by weight of deionized water, and ultrasonically disperse for 10-20 min. Then add 20-30 parts by weight of modified branched alumina, and stir and mix at 200-300 rpm for 90-100 min. After stirring, centrifuge and dry to obtain composite hybrid particles.

5. The method for preparing a composite filler containing silica micropowder according to claim 4, characterized in that, Step S3, the modification of the composite hybrid particles, specifically includes the following steps: S3.1: Add 20-30 parts by weight of the composite hybrid particles to 250-280 parts by weight of deionized water, disperse for 60-70 min, then add p-phenylenediamine, the amount of p-phenylenediamine added is 3-5 wt% of the composite hybrid particles, and add ammonia water to adjust the pH to 11. Then stir and react at 90-92℃ for 3-4 h, then centrifuge, wash and dry to obtain p-phenylenediamine modified composite hybrid particles; S3.2: Add the above p-phenylenediamine modified composite hybrid particles to 100-120 parts by weight of deionized water and disperse for 20-30 min. Then add 3-5 parts by weight of ascorbic acid, stir in a water bath at 80-82℃ and reflux for 8-10 h. After that, filter, wash and freeze dry to obtain the double-modified composite hybrid particles.

6. The method for preparing a composite filler containing silica micropowder according to claim 5, characterized in that, Step S4, the preparation of the composite filler, specifically includes the following steps: The modified silica micro powder and the double-modified composite hybrid particles were mixed in a mass ratio of 10-12:8-10 and placed in a planetary ball mill. Zirconia balls were then added and the mixture was ball-milled for 30-40 minutes to obtain the composite filler.

7. The method for preparing a composite filler containing silica micropowder according to claim 5, characterized in that, The amount of p-phenylenediamine added in step S3.1 is 3-5 wt% of the composite hybrid particles.

8. The method for preparing a composite filler containing silica micropowder according to claim 6, characterized in that, In step S4, the volume ratio of the balls is 3-5:1.

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