CN113929995A - Conductive filler and preparation method thereof, composite conductive material and preparation method of composite conductive rubber - Google Patents
Conductive filler and preparation method thereof, composite conductive material and preparation method of composite conductive rubber Download PDFInfo
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Abstract
The invention discloses a conductive filler and a preparation method thereof, a composite conductive material and a preparation method of composite conductive rubber, and relates to the technical field of conductive materials. The preparation method of the conductive filler comprises the following steps: mixing an aqueous solution of epoxidized natural rubber latex and aminated graphene under a first acidic condition for a crosslinking reaction to obtain a first mixture; and carrying out catalytic polymerization reaction on the first mixture, the aniline monomer and the initiator under a second acidic condition to obtain the aniline monomer. According to the preparation method, the epoxidized natural rubber latex particles and the aminated graphene are crosslinked, so that the graphene is coated on the surfaces of the epoxidized natural rubber latex particles, and then the graphene in the sheet layer is connected by utilizing an aniline monomer, so that a complete conductive path is ensured to be established.
Description
Technical Field
The invention relates to the technical field of conductive materials, in particular to a conductive filler and a preparation method thereof, a composite conductive material and a preparation method of composite conductive rubber.
Background
The electric rubber has great development potential and practical application value in the fields of static electricity resistance, electromagnetic shielding, corrosion prevention and the like as a functional material with the capabilities of conducting electricity and eliminating static charges. Conductive rubbers are generally classified into structural type and composite type. The structural conductive rubber with both rubber elasticity and conductive function is not applied in the laboratory, and the conductive rubber which is usually produced in an industrialized mode is composite conductive rubber, namely, the rubber is used as a matrix and is added with a conductive filler to enable the composite material to obtain the conductive function.
For composite conductive rubber, the type and performance of the filler are the most direct and main factors influencing the conductivity of the composite conductive rubber, and the conductive fillers for the conductive rubber are mainly carbon (mainly graphite, carbon black and carbon fiber), metal (mainly gold, silver, copper, nickel and the like) and metal plated on the particle surface at present. The carbon series is the main conductive filler for preparing the conductive composite rubber at present, but has pollution and is not suitable for preparing conductive materials with color requirements; the metal series and the metal plating on the particle surface have high specific gravity, are difficult to disperse in the polymer, and are not suitable for products with specific gravity requirements. In recent years, graphene is a representative high-dimensional novel carbon-based filler and has attracted extensive attention to the preparation of conductive materials, and great research results have been obtained. The direction of research is to use graphene as a filler to prepare elastic conductive composite materials.
In view of this, the invention is particularly proposed.
Disclosure of Invention
The invention aims to provide a conductive filler and a preparation method thereof, a composite conductive material and a preparation method of composite conductive rubber.
The invention is realized by the following steps:
in a first aspect, the present invention provides a method for preparing a conductive filler, comprising: mixing an aqueous solution of epoxidized natural rubber latex and aminated graphene under a first acidic condition for a crosslinking reaction to obtain a first mixture;
and carrying out catalytic polymerization reaction on the first mixture, the aniline monomer and the initiator under a second acidic condition to obtain the aniline monomer.
In an optional embodiment, water is added into epoxidized natural rubber latex to prepare a solution with the volume percentage concentration of 1-20%, and the aqueous solution of the epoxidized natural rubber latex is obtained after ultrasonic dispersion for 20-40 min;
preferably, the aqueous solution of epoxidized natural rubber latex has a volume percent concentration of 1% to 10%, preferably 1% to 5%;
preferably, the epoxidized natural rubber latex has an epoxidation degree of 10% to 80%, preferably 10% to 50%, more preferably 20% to 40%.
In an alternative embodiment, the mass ratio of the aqueous solution of epoxidized natural rubber latex to the aminated graphene is 1:1 to 100, preferably 1:1 to 50: more preferably 1: 5-15;
preferably, the first acidic condition has a pH of 1 to 5;
preferably, the reaction temperature of the crosslinking reaction is 40-80 ℃, and the reaction time is 1-10 h;
preferably, the reaction temperature of the crosslinking reaction is 50-70 ℃, and the reaction time is 2-4 h.
In an alternative embodiment, catalytically polymerizing the first mixture, the aniline monomer, and the initiator under second acidic conditions comprises: firstly, mixing the first mixture with the aniline monomer, stirring for 2-3h, and then adding the initiator to perform catalytic polymerization reaction;
preferably, the reaction temperature of the catalytic polymerization reaction is 0-4 ℃, and the reaction time is 2-24 h;
preferably, prior to mixing the first mixture with the aniline monomer, mixing the first mixture with an anionic surfactant and adjusting the pH to 1-2 to form the second acidic condition;
preferably, the mass ratio of the added amount of the anionic surfactant to the aminated graphene is 1: 1-100;
preferably, the anionic surfactant comprises at least one of polyvinylpyrrolidone and sodium poly-p-styrenesulfonate;
preferably, the initiator comprises (NH)4)2S2O8、K2Cr2O7、KIO3、FeCl3、H2O2、Ce(SO4)2、MnO2And BPO.
In a second aspect, the present invention provides a conductive filler prepared by the method of preparing a conductive filler according to any one of the above embodiments.
In a third aspect, the present invention provides a composite conductive material, which includes a matrix and the conductive filler according to the foregoing embodiments, wherein the conductive filler is filled in the matrix;
preferably, the matrix comprises rubber, synthetic rubber or plastic.
In a fourth aspect, the present invention provides a method for preparing a composite conductive rubber, which comprises mixing a rubber solution with the conductive filler according to the foregoing embodiment, adding a vulcanizing agent, mixing and stirring to obtain a mixed solution, drying the mixed solution into powder, and hot-pressing the powder.
In an alternative embodiment, the rubber solution is added in an amount such that the mass ratio of the solid content in the rubber solution to the solid content in the conductive filler is 1: 1-10;
preferably, the vulcanizing agent is added in an amount such that the ratio of the solid content of the rubber solution to the solid content of the vulcanizing agent is 100: 1-4;
preferably, the rubber solution is prepared by dissolving natural rubber in a first organic solvent; or dissolving the epoxidized natural rubber in a second organic solvent to obtain the epoxidized natural rubber;
preferably, the first organic solvent comprises at least one of toluene, xylene, and cyclohexane;
preferably, the second organic solvent comprises at least one of chloroform, toluene, and dichloromethane;
preferably, the solids content of the rubber solution is 1 to 10%, preferably 4 to 6%.
In an alternative embodiment, the method of preparing the sulfiding agent comprises: mixing sulfur, zinc diethyldithiocarbamate and toluene to obtain the catalyst;
preferably, the mass ratio of the sulfur to the zinc diethyldithiocarbamate is 1-5: 1; preferably 1-3: 1;
preferably, the curing agent has a solids content of 1-3%.
In an alternative embodiment, the mixed liquor is dried using spray drying;
preferably, the inlet temperature of spray drying is 140-210 ℃, the outlet temperature is 115-150 ℃, the air flow rate is 35-55L/min, and the output power of the peristaltic pump is 5-15%;
preferably, the inlet temperature of spray drying is 170-190 ℃, the outlet temperature is 125-135 ℃, the air flow rate is 35-45L/min, and the output power of the peristaltic pump is 8% -12%;
preferably, the pressure when the powder is hot-pressed is 4-20MPa, the temperature is 125-170 ℃, and the hot-pressing time is 10-20 min;
preferably, the pressure when the powder is hot pressed is 8-12MPa, the temperature is 150-160 ℃, and the hot pressing time is 13-17 min.
The invention has the following beneficial effects:
the utility model provides a preparation method of conductive filler is through carrying out the cross-linking with amination graphite alkene epoxidizing natural rubber latex particle, make graphite alkene cladding in epoxidizing natural rubber latex particle's surface, utilize later aniline monomer to carry out normal position catalytic polymerization and make aniline molecule adsorb on graphite alkene surface, connect the graphite alkene of lamella, and then guarantee to establish complete conductive path, and spherical epoxidizing natural rubber latex particle has certain elasticity, still keep conductive path's integrality under tensile deformation, good electric conductivity has. According to the preparation method of the composite conductive rubber, the conductive filler is mixed with the matrix rubber solution, and the mixture enters the vulcanizing agent to change a non-crosslinking system into a crosslinking system, so that the subsequent hot press molding is easy, the prepared composite conductive rubber still keeps the integrity of a conductive path under the tensile deformation, and the composite conductive rubber has good conductivity.
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In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
Fig. 1 is a schematic structural diagram of each stage of a method for preparing a composite conductive rubber provided in embodiment 1 of the present application.
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. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
In a first aspect, the present invention provides a method for preparing a conductive filler, comprising the steps of:
s101, preparing an aqueous solution of epoxidized natural rubber latex.
And adding water into the epoxidized natural rubber latex to prepare a solution, and performing ultrasonic dispersion for 20-40min to obtain an aqueous solution of the epoxidized natural rubber latex. The epoxidized natural rubber latex has a structure in which rubber particles having a diameter of about 1 micron are suspended in water.
In the present application, the aqueous solution of epoxidized natural rubber latex has a concentration of 1% to 20% by volume, preferably 1% to 10% by volume, more preferably 1% to 5% by volume. The epoxidized natural rubber latex has an epoxidation degree of 10% to 80%, preferably 10% to 50%, more preferably 20% to 40%.
And S102, crosslinking reaction.
Mixing an aqueous solution of epoxidized natural rubber latex and aminated graphene under a first acidic condition to perform a crosslinking reaction to obtain a first mixture.
Wherein the mass ratio of the aqueous solution of the epoxidized natural rubber latex to the aminated graphene is 1:1-100, preferably 1: 1-50: more preferably 1: 5-15. In this example, the pH of the first acidic condition is 1 to 5; the first acidic condition may be adjusted by an acid solution including, but not limited to, hydrochloric acid, formic acid, acetic acid, and the like, preferably hydrochloric acid. The reaction temperature of the crosslinking reaction is 40-80 ℃, and preferably 50-70 ℃; the reaction time is 1-10h, preferably 2-4 h.
Under the first acidic condition, the epoxy groups in the epoxidized natural rubber latex are crosslinked with the amino groups in the aminated graphene, so that the graphene is immobilized on the surface of the epoxidized natural rubber latex particles.
S103, catalyzing polymerization reaction.
And carrying out catalytic polymerization reaction on the first mixture, the aniline monomer and the initiator under a second acidic condition to obtain the aniline monomer. Specifically, the first mixture and aniline monomer are mixed and stirred for 2-3h, and then initiator is added to carry out catalytic polymerization reaction for 2-24h at 0-4 ℃. According to the method, the first mixture and the aniline monomer are mixed and continuously stirred for 2-3 hours, so that the aniline monomer can be loaded on the surface of the epoxidized natural rubber latex particle fixed with graphene, then the initiator is added to carry out in-situ catalytic polymerization reaction, at the moment, the aniline monomer generates polyaniline in situ, and due to the fact that a main chain of the polyaniline is provided with a conjugated group, the polyaniline can generate static electricity, pi-pi conjugation and hydrogen bond interaction with the graphene, and aniline molecules tend to be adsorbed on the surface of the graphene. The polyaniline synthesized in situ connects graphene sheets coated on the surfaces of epoxidized natural rubber latex particles, thereby maintaining the integrity of the conductive path under the condition of tensile deformation.
Preferably, an anionic surfactant can be introduced into the system, so that polyaniline can be more easily adsorbed on the surface of graphene under the action of the anionic surfactant, and a complete conductive path is further ensured to be established. Specifically, prior to mixing the first mixture with aniline monomer, the first mixture is mixed with an anionic surfactant and the pH is adjusted to 1-2 to form second acidic conditions; wherein the mass ratio of the addition amount of the anionic surfactant to the aminated graphene is 1: 1-100; preferably 1:1 to 30; the anionic surfactant comprises at least one of polyvinylpyrrolidone and sodium poly (p-styrene sulfonate).
In this embodiment, there are various initiators that can initiate the catalytic polymerization of aniline monomer, including but not limited to (NH)4)2S2O8、K2Cr2O7、KIO3、FeCl3、H2O2、Ce(SO4)2、MnO2And BPO (benzoyl peroxide)Preferably, the initiator in this application is ammonium persulfate.
The conductive filler prepared by the preparation method of the conductive filler provided by the application still has stable conductivity when the specific elongation is 200%.
In addition, the application also provides a composite conductive material, which comprises a base body and the conductive filler, wherein the conductive filler is filled in the base body; preferably, the matrix comprises rubber, synthetic rubber or plastic.
Specifically, the present application also provides a composite conductive material of a specific base (e.g., rubber), that is, a method for preparing a composite conductive rubber, which includes the steps of:
s201, covering a rubber outer layer.
In the application, the rubber solution is mixed with the conductive filler and stirred for 1-5 hours, so that the matrix rubber solution is fully wrapped on the outer side of the conductive filler.
The rubber solution is prepared by dissolving natural rubber in a first organic solvent; or dissolving the epoxidized natural rubber in a second organic solvent to obtain the epoxidized natural rubber; wherein the first organic solvent comprises at least one of toluene, xylene and cyclohexane, and preferably the first organic solvent is toluene; the second organic solvent comprises at least one of chloroform, toluene and dichloromethane, preferably the second organic solvent is chloroform. The solids content of the rubber solution obtained by the preparation is 1 to 10 percent, and the solid content is preferably 4 to 6 percent.
The adding amount of the rubber solution is calculated according to the solid content ratio of the rubber solution to the conductive filler, and the mass ratio of the solid content in the rubber solution to the solid content in the conductive filler is 1: 1-10.
S202, introducing a vulcanizing agent.
In the application, a vulcanizing agent is added into the system of the step S201 to be mixed and stirred to obtain a mixed solution, and the non-crosslinking system of the step S201 can be changed into a crosslinking system by introducing the vulcanizing agent, so that the subsequent hot press molding is easy.
Specifically, in the present application, the preparation method of the vulcanizing agent comprises the following steps: sulfur, zinc diethyl dithiocarbamate and toluene are mixed to prepare a vulcanizing agent with solid content of 1-3%. Wherein the mass ratio of the sulfur to the zinc diethyldithiocarbamate is 1-5: 1; preferably 1-3: 1.
In the application, the addition amount of the vulcanizing agent is calculated according to the ratio of the solid content of the rubber solution to the solid content of the vulcanizing agent, and the ratio of the solid content of the rubber solution to the solid content of the vulcanizing agent is 100: 1-4;
and S203, hot press molding.
This application is through drying into the powder with mixed liquid, carries out hot briquetting to the powder and can obtain the product that has certain shape. Specifically, the mixed solution is dried by spray drying; the inlet temperature of spray drying is 140-210 ℃, the outlet temperature is 115-150 ℃, the air flow rate is 35-55L/min, and the output power of the peristaltic pump is 5-15%; preferably, the inlet temperature of the spray drying is 170-190 ℃, the outlet temperature is 125-135 ℃, the air flow rate is 35-45L/min, and the output power of the peristaltic pump is 8% -12%. The pressure when the powder is hot-pressed is 4-20MPa, the temperature is 125-170 ℃, and the hot-pressing time is 10-20 min; preferably, the pressure when the powder is hot pressed is 8-12MPa, the temperature is 150-160 ℃, and the hot pressing time is 13-17 min.
The features and properties of the present invention are described in further detail below with reference to examples.
Example 1
The embodiment provides a composite conductive rubber, and a preparation method thereof comprises the following steps:
s1, preparing an aqueous solution of epoxidized natural rubber latex.
Adding water into epoxidized natural rubber latex (with the epoxidation degree of 30%) to prepare a solution with the volume percentage concentration of 5%, and performing ultrasonic dispersion for 20-40min to obtain an aqueous solution of the epoxidized natural rubber latex.
S2, crosslinking reaction.
Mixing an aqueous solution of epoxidized natural rubber latex with aminated graphene under a first acidic condition (pH value of 2), and heating to 60 ℃ to perform a crosslinking reaction for 3 hours to obtain a first mixture. Wherein the mass ratio of the aqueous solution of the epoxidized natural rubber latex to the aminated graphene is 1: 10.
S3, catalyzing polymerization reaction.
Mixing the first mixture with an anionic surfactant (polyvinylpyrrolidone), wherein the mass ratio of the addition amount of the anionic surfactant to the aminated graphene is 1: 20; adjusting the pH value of the system to 1 by using hydrochloric acid, adding aniline monomer, mixing, stirring for 2 hours, and then adding an initiator (ammonium persulfate) to perform catalytic polymerization reaction for 6 hours at the temperature of 2 ℃.
And S4, coating the rubber outer layer.
Mixing a rubber solution (chloroform solution of epoxidized natural rubber, solid content is 5%) with a conductive filler, and stirring for 1-5h, wherein the mass ratio of the solid content in the rubber solution to the solid content in the conductive filler is 1: 8.
s5, introducing a vulcanizing agent.
Mixing sulfur, zinc diethyldithiocarbamate and toluene to prepare a vulcanizing agent with the solid content of 2%, wherein the mass ratio of the sulfur to the zinc diethyldithiocarbamate is 2: 1. Adding a vulcanizing agent into the system of the step S4, mixing and stirring to obtain a mixed solution. The ratio of the solid content of the rubber solution to the solid content of the vulcanizing agent is 100: 2.5.
and S6, hot-press forming.
And (3) drying the mixed solution by spray drying (the inlet temperature is 180 ℃, the outlet temperature is 130 ℃, the air flow rate is 40L/min, and the output power of a peristaltic pump is 10%) to obtain powder, and performing hot press molding on the powder (the pressure is 10MPa, the temperature is 155 ℃, and the hot press time is 15min) to obtain a final sample.
Referring to fig. 1, it can be seen from fig. 1 that the epoxidized natural rubber latex particles provided in the present application are crosslinked with aminated graphene through a crosslinking reaction, so that the graphene is coated on the surface of the epoxidized natural rubber latex particles, and then aniline molecules are adsorbed on the surface of the graphene by using an aniline monomer to perform in-situ catalytic polymerization, so as to connect the graphene in the sheet layer, thereby ensuring that a complete conductive path is established.
Example 2
The embodiment provides a composite conductive rubber, and a preparation method thereof comprises the following steps:
s1, preparing an aqueous solution of epoxidized natural rubber latex.
And adding water into the epoxidized natural rubber latex (the epoxidation degree is 50%) to prepare a solution with the volume percentage concentration of 10%, and performing ultrasonic dispersion for 40min to obtain an aqueous solution of the epoxidized natural rubber latex.
S2, crosslinking reaction.
Mixing an aqueous solution of epoxidized natural rubber latex with aminated graphene under a first acidic condition (pH value of 2), and heating to 80 ℃ to perform a crosslinking reaction for 2h to obtain a first mixture. Wherein the mass ratio of the aqueous solution of the epoxidized natural rubber latex to the aminated graphene is 1: 50.
S3, catalyzing polymerization reaction.
Mixing the first mixture with an anionic surfactant (sodium poly-p-styrene sulfonate) in a mass ratio of 1: 40; adjusting the pH value of the system to 1 by using hydrochloric acid, adding aniline monomer, mixing, stirring for 2 hours, and then adding an initiator (ammonium persulfate) to perform catalytic polymerization reaction for 12 hours at the temperature of 2 ℃.
And S4, coating the rubber outer layer.
Mixing a rubber solution (chloroform solution of epoxidized natural rubber, solid content of 10%) with a conductive filler, and stirring for 3 hours, wherein the mass ratio of the solid content in the rubber solution to the solid content in the conductive filler is 1: 8.
s5, introducing a vulcanizing agent.
Mixing sulfur, zinc diethyldithiocarbamate and toluene to prepare a vulcanizing agent with the solid content of 3%, wherein the mass ratio of the sulfur to the zinc diethyldithiocarbamate is 3: 1. Adding a vulcanizing agent into the system of the step S4, mixing and stirring to obtain a mixed solution. The ratio of the solid content of the rubber solution to the solid content of the vulcanizing agent is 100: 4.
and S6, hot-press forming.
Drying the mixed solution by spray drying (inlet temperature is 210 ℃, outlet temperature is 150 ℃, air flow rate is 55L/min, output power of a peristaltic pump is 15%) into powder, and carrying out hot press molding on the powder (pressure is 20MPa, temperature is 170 ℃, hot press time is 10min) to obtain a product with a certain shape.
Example 3
The embodiment provides a composite conductive rubber, and a preparation method thereof comprises the following steps:
s1, preparing an aqueous solution of epoxidized natural rubber latex.
And adding water into the epoxidized natural rubber latex (the epoxidation degree is 75%) to prepare a solution with the volume percentage concentration of 8%, and performing ultrasonic dispersion for 20min to obtain an aqueous solution of the epoxidized natural rubber latex.
S2, crosslinking reaction.
Mixing an aqueous solution of epoxidized natural rubber latex with aminated graphene under a first acidic condition (pH value of 2), and heating to 50 ℃ to perform a crosslinking reaction for 4 hours to obtain a first mixture. Wherein the mass ratio of the aqueous solution of the epoxidized natural rubber latex to the aminated graphene is 1: 30.
S3, catalyzing polymerization reaction.
Mixing the first mixture with an anionic surfactant (polyvinylpyrrolidone and sodium poly-p-styrene sulfonate) at a mass ratio of 1: 40; adjusting the pH value of the system to 1 by using hydrochloric acid, adding aniline monomer, mixing, stirring for 2 hours, and then adding an initiator (ammonium persulfate) to perform catalytic polymerization reaction for 24 hours at the temperature of 1 ℃.
And S4, coating the rubber outer layer.
Mixing a rubber solution (chloroform solution of epoxidized natural rubber, solid content of 7%) with a conductive filler, and stirring for 2 hours, wherein the mass ratio of the solid content in the rubber solution to the solid content in the conductive filler is 1: 8.
s5, introducing a vulcanizing agent.
Mixing sulfur, zinc diethyldithiocarbamate and toluene to prepare a vulcanizing agent with the solid content of 3%, wherein the mass ratio of the sulfur to the zinc diethyldithiocarbamate is 3: 1. Adding a vulcanizing agent into the system of the step S4, mixing and stirring to obtain a mixed solution. The ratio of the solid content of the rubber solution to the solid content of the vulcanizing agent is 100: 1;
and S6, hot-press forming.
Drying the mixed solution by spray drying (inlet temperature is 140 ℃, outlet temperature is 115 ℃, air flow rate is 35L/min, output power of a peristaltic pump is 5%) into powder, and carrying out hot press molding on the powder (pressure is 8MPa, temperature is 130 ℃, hot press time is 20min) to obtain a product with a certain shape.
Example 4
The difference from example 1 is that "the mass ratio of the solid content in the rubber solution to the solid content in the conductive filler in S4 is 1: 1".
Comparative example 1
The epoxidized natural rubber latex in step S1 of example 1 was replaced with natural rubber latex.
Comparative example 2
The aminated graphene in step S1 of example 1 was replaced with graphene.
Comparative example 3
Step S3 of embodiment 1 is omitted.
Comparative example 4
Instead of preparing polyaniline and then performing catalytic polymerization in step S3 in example 1, the method specifically includes: firstly, carrying out catalytic polymerization reaction on an aniline monomer and an initiator (ammonium persulfate) at the temperature of 2 ℃ for 6 hours to obtain polyaniline; mixing the first mixture with an anionic surfactant (polyvinylpyrrolidone), wherein the mass ratio of the addition amount of the anionic surfactant to the aminated graphene is 1: 20; adjusting the pH value of the system to 1 by using hydrochloric acid, adding polyaniline and stirring for 2 hours.
The samples prepared in examples 1 to 4 and comparative examples 1 to 4 were subjected to a test for conductivity under tensile deformation, and the test results were as follows:
as can be seen from the data of comparative examples 1 and 2, when the epoxidized natural rubber latex was changed to natural rubber latex or the aminated graphene was changed to graphene, crosslinking could not be performed due to lack of epoxy group or amino group, and further the graphene could not be immobilized on the surface of the epoxidized natural rubber latex particles, resulting in a significant decrease in conductivity as the tensile deformation rate was increased.
As can be seen from the data of comparative example 3, when step S3 of example 1 is omitted, i.e., the catalytic polymerization reaction is omitted, the graphene sheets coated on the surfaces of the epoxidized natural rubber latex particles lack the linking effect of polyaniline, and thus the conductivity thereof is significantly reduced under the condition of tensile deformation.
As can be seen from the data of comparative example 4, the polyaniline prepared in advance is directly adsorbed on the surface of graphene, and at this time, the aniline monomer has reacted to generate polyaniline, which cannot be loaded on the surface of the epoxidized natural rubber latex particles on which graphene is fixed, and thus polyaniline cannot be generated in situ to form a conductive path, and further the conductivity is significantly reduced under the condition of tensile deformation.
According to the preparation method, the epoxidized natural rubber particles are fixed by the amino graphene, the polyaniline is used for fixing the conductive network, and finally the vulcanizing agent and the organic solution of the rubber are used for establishing the stable shell for the composite material, but the shell layer is not too thick, so that the preparation of the conductive material in a stretching state is realized.
To sum up, the preparation method of the conductive filler provided by the application comprises the steps of crosslinking the epoxidized natural rubber latex particles with the aminated graphene, coating the graphene on the surfaces of the epoxidized natural rubber latex particles, then carrying out in-situ catalytic polymerization by using an aniline monomer to enable aniline molecules to be adsorbed on the surfaces of the graphene, and connecting the graphene in the sheet layer, so that a complete conductive path is established, and the spherical epoxidized natural rubber latex particles have certain elasticity, so that the completeness of the conductive path is still kept under tensile deformation, and the conductive filler has good conductivity. According to the preparation method of the composite conductive rubber, the conductive filler is mixed with the matrix rubber solution, and the mixture enters the vulcanizing agent to change a non-crosslinking system into a crosslinking system, so that the subsequent hot press molding is easy, the prepared composite conductive rubber still keeps the integrity of a conductive path under the tensile deformation, and the composite conductive rubber has good conductivity.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A method for preparing a conductive filler, comprising: mixing an aqueous solution of epoxidized natural rubber latex and aminated graphene under a first acidic condition for a crosslinking reaction to obtain a first mixture;
and carrying out catalytic polymerization reaction on the first mixture, the aniline monomer and the initiator under a second acidic condition to obtain the aniline monomer.
2. The method for preparing the conductive filler according to claim 1, wherein the epoxidized natural rubber latex is added with water to prepare a solution with a volume percentage concentration of 1-20%, and the aqueous solution of the epoxidized natural rubber latex is obtained after ultrasonic dispersion for 20-40 min;
preferably, the aqueous solution of epoxidized natural rubber latex has a volume percent concentration of 1% to 10%, preferably 1% to 5%;
preferably, the epoxidized natural rubber latex has an epoxidation degree of 10% to 80%, preferably 10% to 50%, more preferably 20% to 40%.
3. The method for producing the conductive filler according to claim 1, wherein the mass ratio of the aqueous solution of the epoxidized natural rubber latex to the aminated graphene is 1:1 to 100, preferably 1:1 to 50: more preferably 1: 5-15;
preferably, the first acidic condition has a pH of 1 to 5;
preferably, the reaction temperature of the crosslinking reaction is 40-80 ℃, and the reaction time is 1-10 h;
preferably, the reaction temperature of the crosslinking reaction is 50-70 ℃, and the reaction time is 2-4 h.
4. The method of preparing the conductive filler according to claim 1, wherein catalytically polymerizing the first mixture, the aniline monomer, and the initiator under the second acidic condition comprises: firstly, mixing the first mixture with the aniline monomer, stirring for 2-3h, and then adding the initiator to perform catalytic polymerization reaction;
preferably, the reaction temperature of the catalytic polymerization reaction is 0-4 ℃, and the reaction time is 2-24 h;
preferably, prior to mixing the first mixture with the aniline monomer, mixing the first mixture with an anionic surfactant and adjusting the pH to 1-2 to form the second acidic condition;
preferably, the mass ratio of the added amount of the anionic surfactant to the aminated graphene is 1: 1-100;
preferably, the anionic surfactant comprises at least one of polyvinylpyrrolidone and sodium poly-p-styrenesulfonate;
preferably, the initiator comprises (NH)4)2S2O8、K2Cr2O7、KIO3、FeCl3、H2O2、Ce(SO4)2、MnO2And BPO.
5. A conductive filler, characterized in that it is produced by the method for producing a conductive filler according to any one of claims 1 to 4.
6. A composite conductive material comprising a matrix and the conductive filler according to claim 5, wherein the conductive filler is filled in the matrix;
preferably, the matrix comprises rubber, synthetic rubber or plastic.
7. A preparation method of composite conductive rubber is characterized in that a rubber solution is mixed with the conductive filler according to claim 5, then a vulcanizing agent is added to be mixed and stirred to obtain a mixed solution, the mixed solution is dried into powder, and the powder is subjected to hot pressing to obtain the composite conductive rubber.
8. The method for preparing the composite conductive rubber according to claim 7, wherein the rubber solution is added in an amount such that the mass ratio of the solid content in the rubber solution to the solid content in the conductive filler is 1: 1-10;
preferably, the vulcanizing agent is added in an amount such that the ratio of the solid content of the rubber solution to the solid content of the vulcanizing agent is 100: 1-4;
preferably, the rubber solution is prepared by dissolving natural rubber in a first organic solvent; or dissolving the epoxidized natural rubber in a second organic solvent to obtain the epoxidized natural rubber;
preferably, the first organic solvent comprises at least one of toluene, xylene, and cyclohexane;
preferably, the second organic solvent comprises at least one of chloroform, toluene, and dichloromethane;
preferably, the solids content of the rubber solution is 1 to 10%, preferably 4 to 6%.
9. The method for producing a composite conductive rubber according to claim 7, wherein the vulcanizing agent is produced by: mixing sulfur, zinc diethyldithiocarbamate and toluene to obtain the catalyst;
preferably, the mass ratio of the sulfur to the zinc diethyldithiocarbamate is 1-5: 1; preferably 1-3: 1;
preferably, the curing agent has a solids content of 1-3%.
10. The method for preparing the composite conductive rubber according to claim 7, wherein the mixed solution is dried by spray drying;
preferably, the inlet temperature of spray drying is 140-210 ℃, the outlet temperature is 115-150 ℃, the air flow rate is 35-55L/min, and the output power of the peristaltic pump is 5-15%;
preferably, the inlet temperature of spray drying is 170-190 ℃, the outlet temperature is 125-135 ℃, the air flow rate is 35-45L/min, and the output power of the peristaltic pump is 8% -12%;
preferably, the pressure when the powder is hot-pressed is 4-20MPa, the temperature is 125-170 ℃, and the hot-pressing time is 10-20 min;
preferably, the pressure when the powder is hot pressed is 8-12MPa, the temperature is 150-160 ℃, and the hot pressing time is 13-17 min.
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