1. A preparation method of a graphene prepreg with a three-dimensional network structure is characterized by comprising the following steps: the graphene prepreg is prepared by continuously preparing a solution mixing, drying and hot melting composite process by taking semi-cured resin particles and graphene powder as raw materials.

2. The method of claim 1, wherein: the semi-cured resin is a semi-cured epoxy resin system or a semi-cured bismaleimide resin system which is insoluble or insoluble in a solvent.

3. The method of claim 2, wherein: the semi-cured epoxy resin system comprises epoxy resin and a curing agent and other fillers which are matched with the epoxy resin.

4. The method of claim 2, wherein: the semi-cured bismaleimide resin system comprises bismaleimide resin, a curing agent matched with the bismaleimide resin and other fillers.

5. The method of claim 1, wherein: the particle diameter of the semi-solidified resin particles is 500nm-20 um.

6. The method of claim 1, wherein: the graphene powder is one or more of reduced graphene oxide, graphene nanosheets and expanded graphene, and the diameter of the lamella is smaller than or equal to the particle size of the resin particles.

7. The method of claim 1, wherein: the preparation method comprises the following specific steps:

step one, slurry preparation: according to the requirements, a graphene prepreg formula is formulated, resin particles, graphene powder and auxiliary materials are weighed and poured into a container filled with a solvent, and the mixture is ultrasonically stirred and uniformly mixed to prepare graphene/resin particle slurry with the concentration of 50-200 mg/ml;

step two, coating: pouring the slurry into a glue groove, starting a conveying system, and scraping the slurry into a film with the thickness of 0.3-1.5mm by using a scraper and a baffle plate;

step three, drying to form a film: conveying the scraped film to a heating area through a conveying system, and drying at 50-110 ℃ to obtain a graphene/resin particle film;

when the solvent is ethanol, the heating temperature is 50-80 ℃, and when the solvent is deionized water, the heating temperature is 80-110 ℃;

the heating temperature of the bismaleimide resin system is higher than that of the epoxy resin system;

step four, hot melting and compounding: conveying the film to the front end of a compression roller platform of a pre-dipping machine through a conveying system, realizing hot melt compounding of graphene and resin particles through the action of a heating platform and a compression roller of the pre-dipping machine, and performing compression roller treatment with a roller gap of 0.25mm-1.00mm at the temperature of 60-120 ℃ to obtain graphene prepreg; compounding temperature is related to the resin used:

when preparing the graphene/epoxy resin prepreg, the compounding temperature is 60-120 ℃;

when the graphene/bismaleimide resin prepreg is prepared, the compounding temperature is 80-120 ℃.

8. The method of claim 7, wherein: in the first step, the auxiliary material is one or more of sodium dodecyl benzene sulfonate, polyvinyl alcohol, sodium polyoxyethylene alkyl ether sulfate and poly (N-acyl ethylene imine).

9. The method of claim 7, wherein: in the first step, the solvent is deionized water or/and ethanol.

10. The method of claim 7, wherein: the conveying speed of the conveying system is 0.2-2 m/min.

Background

The fiber resin matrix composite material has the advantages of good manufacturability, high specific strength and specific stiffness, light weight, small density, low cost and the like, so the fiber resin matrix composite material is widely applied to the aspects of aerospace, ships, automobiles, sports, daily life and the like. In the field of aeronautics in particular, resin-based composite materials have been replacing metal materials in the last 30 years, with a growing proportion of their use in aircraft. However, the existing resin-based composite materials have defects in certain aspects and cannot meet the requirements of certain specific places. For example, even the carbon fiber with the best conductivity cannot form a good conductive network in the resin matrix, so compared with a metal material, the resin matrix composite material has poor conductivity, and when the resin matrix composite material is used as an airplane body, a large amount of charges cannot be rapidly dispersed but gather near an initial attachment area to generate high temperature when the airplane body is struck by lightning, so that the composite material is delaminated and ablated, the composite material is seriously damaged, the performance is greatly reduced, and the flight safety is endangered. In addition, strong electromagnetic fields can be generated, so that electronic equipment on the airplane fails or is damaged, and normal flight of the airplane is affected; even the composite material is punctured, sparks are generated inside the airplane, and the danger of oil tank explosion and the like is caused.

The resin-based composite material is prepared by paving carbon fiber prepreg or other prepregs into a preformed body and curing and molding the preformed body by an autoclave. Therefore, development of a novel prepreg is one of effective solutions. The graphene is a two-dimensional material formed by arranging carbon atoms in a six-membered ring form, has the advantages of excellent conductivity, light weight, low density and the like, and the graphene prepreg prepared by hot-melting compounding the graphene and semi-cured resin can well make up the defect of poor conductivity of the traditional prepreg and the composite material thereof through surface modification. Particularly, the dispersion state of the graphene is accurately controlled, and the graphene is dispersed in the resin matrix in a three-dimensional network structure mode, so that a finished product (prepreg, composite material and the like) can obtain higher conductivity under the condition of lower graphene content, and meanwhile, negative effects on other performances are not caused.

CN201410459232.3 discloses a preparation method of a graphene prepreg, which comprises preparing graphene paper by a press-coating method with a flat-plate vulcanizing machine, and then compounding the graphene paper with a semi-cured epoxy resin adhesive film to obtain the graphene prepreg. The graphene prepreg prepared by the method is formed by stacking graphene and epoxy resin in a layered form, and the graphene and the epoxy resin are not mutually infiltrated. Meanwhile, the product is not in the form of a traditional coil but in the form of a sheet, so that the production efficiency is low, and the requirement of batch production is not met.

CN201810024685.1 discloses a method for preparing a graphene film prepreg, which comprises preparing a graphene film having a three-dimensional network structure or a porous structure from graphene, and then hot-melting and compounding the graphene film with a resin adhesive film to prepare the graphene film prepreg. In the method, the resin needs to be immersed into the graphene film with a three-dimensional network structure or a porous structure through high-temperature melting in the hot-melt compounding process. Although continuous preparation of the graphene film prepreg is realized, the hot-melt compounding time is short, and the graphene film is difficult to be fully infiltrated by the resin. Sometimes, there are areas of prepreg that are not wetted, which can have a significant effect on the quality of the product.

CN201510607806.1 discloses a method for preparing graphene paper prepreg, which comprises preparing a self-supporting graphene paper-like material by using ultrasound, microfiltration membrane vacuum filtration and heat treatment, then impregnating the material in a mixed solution of epoxy resin and a solvent, and heating to remove the solvent to obtain the resin-impregnated graphene paper prepreg. Graphene in the graphene paper prepreg prepared by the method is fully soaked by epoxy resin, but the graphene paper prepreg is not suitable for large-scale batch production.

Disclosure of Invention

The purpose of the invention is: the preparation method of the graphene prepreg with the three-dimensional network structure is designed and provided for solving the problems in the prior art.

In order to solve the technical problem, the technical scheme of the invention is as follows:

a preparation method of a graphene prepreg with a three-dimensional network structure is characterized in that the graphene prepreg is prepared by taking semi-cured resin particles and graphene powder as raw materials and continuously preparing the raw materials through solution mixing, drying and hot melting compounding processes.

Before use, the particle diameter of the semi-cured resin particles is 500nm to 20um by a method of pulverization, grinding, or the like.

In the solution mixing process, resin is dispersed in the solution in the form of particles with the particle size of 500nm-20um, and the graphene sheet layer wraps the resin particles; in the drying process, the solvent is gradually removed at a certain temperature, and the resin particles have certain viscosity to adhere the surrounding graphene sheet layers on the surface. During hot melt compounding, under the action of certain temperature and pressure, resin particles are molten, have certain fluidity, can partially infiltrate into or partially extrude from the graphene sheet layer wrapped outside, provide certain strength for the prepreg through bonding, and the graphene sheet layer wrapped outside efficiently constructs a three-dimensional conductive network.

The semi-cured resin is a semi-cured epoxy resin system or a semi-cured bismaleimide resin system which is insoluble or insoluble in a solvent;

semi-cured epoxy resin system: comprises epoxy resin and matched curing agent and other fillers.

Semi-cured bismaleimide resin system: comprises bismaleimide resin and a matched curing agent and other fillers.

The semi-cured epoxy resin system or the semi-cured bismaleimide resin system is an existing material system.

The graphene powder is one or more of reduced graphene oxide, graphene nanosheets and expanded graphene, and the diameter of a lamella of the graphene powder is smaller than or equal to the particle size of the resin particles;

the preparation method comprises the following specific steps:

step one, slurry preparation: according to the requirements, a graphene prepreg formula is formulated, resin particles, graphene powder and auxiliary materials are weighed and poured into a container filled with a solvent, and the mixture is ultrasonically stirred and uniformly mixed to prepare graphene/resin particle slurry with the concentration of 50-200 mg/ml;

step two, coating: pouring the slurry into a glue groove, starting a conveying system, and scraping the slurry into a film with the thickness of 0.3-1.5mm by using a scraper and a baffle plate;

step three, drying to form a film: conveying the scraped film to a heating area through a conveying system, and drying at 50-110 ℃ to obtain a graphene/resin particle film; the heating temperature is related to the melting point and viscosity of the solvent, resin used; when the solvent is ethanol, the heating temperature is 50-80 ℃, and when the solvent is deionized water, the heating temperature is 80-110 ℃; the heating temperature of the bismaleimide resin system is higher than that of the epoxy resin system;

step four, hot melting and compounding: conveying the film to the front end of a compression roller platform of a pre-dipping machine through a conveying system, realizing hot melt compounding of graphene and resin particles through the action of a heating platform and a compression roller of the pre-dipping machine, and performing compression roller treatment with a roller gap of 0.25mm-1.00mm at the temperature of 60-120 ℃ to obtain graphene prepreg; compounding temperature is related to the resin used:

when preparing the graphene/epoxy resin prepreg, the compounding temperature is 60-120 ℃;

when preparing the graphene/bismaleimide resin prepreg, the compounding temperature is 80-120 ℃;

the conveying speed in the conveying system is 0.2-2 m/min.

In the first step, the auxiliary material is one or more of sodium dodecyl benzene sulfonate, polyvinyl alcohol, sodium polyoxyethylene alkyl ether sulfate and poly (N-acyl ethylene imine);

in the first step, the solvent is deionized water or/and ethanol.

The invention has the advantages and beneficial effects that:

the graphene prepreg provided by the invention has the following advantages and excellent effects:

firstly, the continuous preparation determines that the graphene prepreg has the capacity of mass production, and can well meet the requirement of large-scale application. The processes of coating, film forming, hot melting, compounding and the like of the graphene prepreg are all completed on one production line, and the graphene prepreg can be continuously produced under the condition of continuous supplement of slurry.

Secondly, the resin is wrapped by graphene in the form of particles, so that graphene sheets can be efficiently utilized to construct a three-dimensional conductive network.

Compared with a direct mixing mode of resin fluid and graphene powder, the use amount of graphene is greatly reduced, so that the conductivity of the material is remarkably improved;

compared with a resin adhesive film hot-melt impregnated graphene film, the resin particles are wrapped in the graphene sheet layer in advance, so that the resin can better infiltrate the graphene sheet layer, and the defects of glue shortage and the like are reduced.

And thirdly, the graphene prepreg is used as a functional prepreg and is paved on the surface of a preformed body formed by other structural prepregs to play an auxiliary role, so that the required functions are provided for the composite material. According to the components of other structural prepregs, the same resin system is selected to prepare the graphene prepreg, so that the graphene prepreg and other structural prepregs can be co-cured to prepare the composite material, the preparation process is simple and efficient, and the manufacturing cost is obviously reduced.

Fourthly, meanwhile, the prepared composite material has good lightning stroke resistance and great application value.

Drawings

In order to more clearly illustrate the technical solution of the present invention, the drawings used in the embodiment of the present invention will be briefly explained. It is obvious that the drawings described below are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be obtained from these drawings without inventive effort.

Fig. 1 is a schematic diagram of a preparation principle of a graphene prepreg, in which a small short line is graphene powder, and a circle represents a semi-cured resin particle;

fig. 2 is a photograph of the front and back sides of (a, b) the carbon fiber resin-based composite material and (c, d) the graphene-modified carbon fiber resin-based composite material after lightning strike.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Features of various aspects of embodiments of the invention will be described in detail below. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without these specific details. The following description of the embodiments is merely intended to better understand the present invention by illustrating examples thereof. The present invention is not limited to any particular arrangement or method provided below, but rather covers all product structures, any modifications, alterations, etc. of the method covered without departing from the spirit of the invention.

In the drawings and the following description, well-known structures and techniques are not shown to avoid unnecessarily obscuring the present invention.

The schematic diagram of the preparation method of the prepreg is shown in fig. 1, and in the solution mixing process, the resin particles, the graphene powder and the auxiliary material are poured into a container containing a solvent, and the resin particles, the graphene powder and the auxiliary material are stirred and mixed uniformly by ultrasound. Wherein the resin is dispersed in the solution in the form of particles with the particle diameter of 500nm-20um, and the graphene sheet layer wraps the resin particles. In the drying process, the solvent is gradually removed at a certain temperature, and the resin particles have certain viscosity to adhere the surrounding graphene sheet layers on the surface. During hot melt compounding, under the action of certain temperature and pressure, resin particles are molten, have certain fluidity, can partially infiltrate into or partially extrude from the graphene sheet layer wrapped outside, provide certain strength for the prepreg through bonding, and the graphene sheet layer wrapped outside efficiently constructs a three-dimensional conductive network.

The detailed procedures of the present invention will be further described with reference to the following examples:

example one (bismaleimide resin/water):

slurry preparation: weighing 40g of bismaleimide resin particles, 20g of graphene powder and 0.40g of polyvinyl alcohol, pouring into a container filled with 300ml of deionized water, and performing ultrasonic stirring and uniform mixing to prepare graphene/bismaleimide resin particle slurry with the concentration of about 200 mg/ml;

coating: pouring the slurry into a glue tank, starting a conveying system, and scraping the slurry into a film with the thickness of 1.2mm by using a scraper and a baffle plate, wherein the conveying speed is 1 m/min;

thirdly, drying and film forming: conveying the scraped film to a heating area through a conveying system, and drying at 90 ℃ to obtain a graphene/bismaleimide resin microparticle film;

fourthly, hot melting and compounding: the film is conveyed to the front end of a compression roller platform of a pre-dipping machine through a conveying system, the hot melting compounding of graphene and resin particles is realized through the action of a heating platform and a compression roller of the pre-dipping machine, and the graphene prepreg is obtained through the treatment of 1-3 groups of compression rollers (the roller gaps are 0.75mm, 0.50mm and 0.25mm respectively) at the temperature of 110 ℃.

Example two (epoxy/ethanol):

slurry preparation: weighing 30g of epoxy resin particles, 15g of graphene powder and 0.45g of sodium dodecyl benzene sulfonate, pouring into a container filled with 300ml of ethanol, and ultrasonically stirring and uniformly mixing to prepare graphene/epoxy resin particle slurry with the concentration of about 150 mg/ml;

coating: pouring the slurry into a glue groove, starting a conveying system, and scraping the slurry into a film with the thickness of 0.8mm by using a scraper and a baffle plate, wherein the conveying speed is 2 m/min;

thirdly, drying and film forming: conveying the scraped film to a heating area through a conveying system, and drying at 60 ℃ to obtain a graphene/epoxy resin particle film;

fourthly, hot melting and compounding: the film is conveyed to the front end of a compression roller platform of a pre-dipping machine through a conveying system, the hot melting compounding of graphene and resin particles is realized through the action of a heating platform and a compression roller of the pre-dipping machine, and the graphene prepreg is obtained through the treatment of 1-3 groups of compression rollers (the roller gaps are 0.50mm, 0.35mm and 0.25mm respectively) at the temperature of 80 ℃.

For example 2, lightning strike resistance tests are compared, and as shown in fig. 2, (a) and b) are photos of the front side and the back side of the carbon fiber resin-based composite material after lightning strike, and (c) and d) are photos of the front side and the back side of the graphene-modified carbon fiber resin-based composite material after lightning strike, it can be seen that the carbon fiber resin-based composite material is directly punctured, but the carbon fiber resin-based composite material with the surface modified by the graphene prepreg is not punctured, and the damage condition is obviously better than that of the former.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive various equivalent modifications or substitutions within the technical scope of the present invention, and these modifications or substitutions should be covered within the scope of the present invention.