CN116313338A - PTC based on vertically oriented graphene as conductive material and preparation method thereof - Google Patents
PTC based on vertically oriented graphene as conductive material and preparation method thereof Download PDFInfo
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- H—ELECTRICITY
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- H01C—RESISTORS
- H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
- H01C7/02—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having positive temperature coefficient
- H01C7/021—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having positive temperature coefficient formed as one or more layers or coatings
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- H—ELECTRICITY
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- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
- H01B1/02—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of metals or alloys
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- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
- H01B1/04—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of carbon-silicon compounds, carbon or silicon
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
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- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
- H01B1/06—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of other non-metallic substances
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- H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
- H01C7/02—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having positive temperature coefficient
- H01C7/028—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having positive temperature coefficient consisting of organic substances
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Abstract
The invention provides a PTC based on vertically oriented graphene as a conductive material and a manufacturing method thereof, wherein a high polymer is used as a matrix, and graphene particles oriented in the direction perpendicular to an electrode plane are contained, and are dispersed in the polymer matrix along the direction perpendicular to an electrode plate, so that the resistance of the PTC can be greatly reduced by utilizing the high conductivity in the graphene plate layer. The method comprises the following four steps: firstly, preparing a thin sheet with the thickness of 0.1-5 mm by using methods such as casting, hot pressing and the like, wherein the graphene inside the thin sheet is oriented in parallel along the plane of the thin film under the action of a flowing field; secondly, stacking the thin sheets obtained in the first step, and performing hot pressing to obtain a polymer/graphene composite with a certain thickness and an orientation structure; thirdly, cutting the graphene into a film by mechanical force along the direction perpendicular to the orientation direction of the graphene, wherein the film retains the orientation structures of the first step and the second step; and fourthly, coating an electrode plate on the cutting surface to prepare the PTC product based on the graphene which is oriented vertically to the electrode plate as a conductive material. The method can orient the graphene in a direction favorable for conduction, fully utilize high conductivity in the graphene layer, greatly reduce the room temperature resistance of the PTC and reduce the loss of the PTC in a circuit.
Description
Technical Field
The invention mainly relates to a high polymer-based resistor device or device with positive temperature coefficient resistivity, in particular to a PTC based on vertically oriented graphene as a conductive material and a preparation method thereof.
Background
By dispersing the conductive particles in some crystalline or semi-crystalline polymers, nonlinear sudden increases in the composite resistance occur in a specific temperature range, and by utilizing the characteristic, a polymer-based high-molecular PTC material can be prepared. Since the discovery of this phenomenon in Frydman1945, polymeric PTC has become a hotspot for the development and research of self-limiting thermal fuses. The polymer matrix commonly used as the high molecular PTC is polyethylene, polyvinylidene fluoride, polypropylene, ethylene-vinyl acetate copolymer, etc., and the conductive filler is carbon black, graphite, carbon fiber, metal powder, conductive ceramic powder, etc.
Miniaturization and low power consumption are major trends in future development of electronic components, and PTC is also being developed toward this trend in electronic circuits as a circuit protection component. The common conductive materials for PTC include carbon black, graphite, conductive ceramic powder, metal powder and the like, wherein the carbon black PTC has the advantage of stable electrical property, but the resistance cannot be further reduced, the conductive properties of the conductive ceramic powder and the metal powder are better than those of the carbon black, and the prepared PTC material has lower resistance, but is easily influenced by oxygen, moisture and the like, and the electrical property is not as long-term stable as that of the carbon black PTC.
In order to reduce the loss of the PTC product in the circuit, the normal temperature resistance of the product needs to be reduced as much as possible, and the conventional scheme for filling conductive materials such as ceramic powder, metal powder and the like can achieve very low product resistance, but is easily influenced by moisture and the like, and the long-term performance is not outstanding.
Graphene is a material known to have the best conductivity at normal temperature, and is a two-dimensional planar structure at a microscopic level, which has extremely high conductivity in the layer and high conductivity between layers. Therefore, when graphene is used as a conductive filler for PTC, graphene has a problem of orientation direction in a polymer matrix.
Generally, in the PTC core material with graphene prepared by tape casting and calendaring, the graphene is horizontally oriented along with a flow field, and the copper foil of the pole piece is also coated on two sides of the core material along the horizontal direction, so that the PTC prepared by the method cannot fully utilize the high conductivity of the graphene, and thus the prepared PTC initial resistance is still higher.
Disclosure of Invention
The invention aims at: provided is a vertically oriented graphene-based conductive film.
Still another object of the present invention is: the application of the conductive film based on the vertically oriented graphene in the PTC core material is provided, and the purpose of reducing the PTC resistance is achieved by utilizing the fact that the graphene has extremely high conductivity in the orientation direction and is oriented perpendicular to the direction of the electrode plate.
Another object of the present invention is to provide a method for manufacturing the PTC based on the vertically oriented graphene as a conductive material.
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
a conductive film based on vertically oriented graphene takes a high molecular polymer as a matrix, and conductive materials are added into the high molecular polymer to form a film, wherein the conductive materials comprise graphene particles with a two-dimensional structure and other conductive fillers, and the graphene particles are dispersed in the polymer matrix along the direction perpendicular to the plane of the film.
Further, the radial dimension of the graphene is 10 nm-1 mm.
Further, the conductive filler comprises one or more of graphite black, graphite, conductive ceramic powder and metal powder, and is dispersed into a conductive network in the high polymer, and the communication among the graphene particles is realized.
The composite film material is formed by graphene, conductive filler and high polymer, wherein at least part of the graphene is perpendicular to the surface of the film to form an oriented network, and the composite film material of the oriented graphene, conductive particles and high polymer is formed.
Further, the vertical-orientation graphene-based conductive film is characterized in that: comprising the following steps:
firstly, blending a high polymer with the content of 10-90 wt% and a conductive material containing 0.1-30 wt% of graphene particles, performing tape casting film forming, and performing hot pressing on a high polymer-based mixture to prepare a thin sheet with the thickness of 0.1-5 mm, wherein the graphene inside the thin sheet is parallel oriented along the plane of the thin film under the action of a flowing field;
secondly, stacking the thin sheets obtained in the first step, wherein the stacking number is 1-100, and hot pressing to obtain a polymer/graphene composite with a certain thickness and an orientation structure;
and thirdly, cutting the graphene into a film along a direction perpendicular to the orientation direction of the graphene, and obtaining the film with high conductivity in the orientation direction.
In the first step, the orientation treatment mode also comprises one or more modes of electrostatic spinning, melt spinning, twin-screw extrusion, tape casting film forming, open mill film forming, spin coating, solution blending, layer-by-layer self-assembly, vacuum auxiliary forming and the like.
The present invention provides the use of graphene/polymer composites with high conductivity in the vertical direction. In particular to application of a conductive film based on vertically oriented graphene to PTC resistor products.
The vertically oriented graphene, conductive particles and polymer composite material can be used as core materials of PTC known in the industry, including battery piece type PTC, plug-in type PTC and surface mounting type PTC, so as to meet various special requirements under different use conditions, and can be applied to the protection of electronic circuit systems such as lithium batteries, circuit boards, motors and the like.
The preparation method of the PTC product by the graphene, the conductive filler and the high polymer composite film comprises the following steps:
first, preparing graphene, conductive particles and polymer composite film materials, wherein the graphene is oriented along a plane direction.
The conductive filler is used as a main conductive network, and communication between the graphenes is realized. The conductive material comprises one or more of carbon black, graphite, conductive ceramic powder, metal powder and the like;
the orientation treatment mode comprises one or more modes of electrostatic spinning, melt spinning, twin-screw extrusion, casting film forming, open mill film forming, spin coating, solution blending, layer-by-layer self-assembly, vacuum auxiliary forming and the like;
wherein the thickness of the film is 0.1-5 mm.
Wherein the graphene material comprises one or more of single-layer graphene, multi-layer graphene, oxidized graphene, redox graphene, expanded exfoliated graphene, liquid-phase dissociated graphene, N-doped graphene and three-dimensional graphene.
Further, the radial dimension of the graphene is 10 nm-1 mm, the thickness is 0.34 nm-1 mm, and the number of layers is 1-100.
The content of the graphene is 0.1-30wt%, the content of the conductive particles is 0-60wt%, and the content of the polymer matrix is 10-90wt%.
And secondly, stacking the graphene, the conductive particles and the polymer composite film material, which are oriented along the plane direction, of the graphene prepared in the first step layer by layer, placing the stacked graphene, the conductive particles and the polymer composite film material in a die cavity for fixation, heating and melting, cooling, and cutting the stacked graphene into films along the stacking direction.
The cutting method comprises one or more of common mechanical cutting, diamond wire cutting, machine tool cutting, polishing and thinning and the like.
Wherein the thickness of the cut film is 0.1-5 mm.
According to the invention, the graphene can be vertically oriented along the copper foil and dispersed in the polymer and the carbon black, so that the inner high conductivity of the graphene can be fully utilized to prepare the PTC material with low resistance, and meanwhile, the damage to long-term performance caused by oxygen and moisture is avoided.
A PTC core material containing vertically oriented graphene, wherein the graphene is perpendicular to the direction in which the plane of an electrode is located, and has extremely high conductivity in the direction, so that the resistance of the PTC core material can be greatly reduced. The manufacturing method of the PTC core material comprises the following steps:
and coating conductive metal foils on two sides of the graphene, conductive particles and polymer composite film material which are oriented in the direction perpendicular to the plane as electrode plates, so as to realize the function of double-sided conduction.
Methods in which electrode sheets are coated include, but are not limited to: one or more of metal foil hot pressing, electroplating, electroless plating and vacuum spraying. In order to minimize damage to the alignment structure, one or more of electroplating, electroless plating, and vacuum plating are preferred.
If metal foil hot-pressing is selected as the electrode plate, the hot-pressing temperature is 130-190 ℃, preferably 160-180 ℃; the pressure of the hot pressing is 5-100 MPa, preferably 10-30 MPa.
Advantages of the PTC core of the present invention compared to existing polymer-based PTC core materials include:
(1) According to the invention, the graphene is dispersed into the polymer, and the horizontal orientation of the graphene in the composite system is realized by utilizing the orientation property of the graphene along with the flowing field. And then carrying out lamination hot pressing and cutting from a specific direction to realize the vertical orientation of the graphene in the composite system. The PTC chip manufactured by the method has the characteristic of ultralow resistance by utilizing ultrahigh conductivity in the graphene layer and conductivity in the orientation direction being far higher than that in other directions. Has wide application prospect in the aspect of realizing PTC miniaturization and large current.
(2) The PTC core material containing the vertical graphene can realize high conductivity of metal powder and conductive ceramic powder series, long-term stability of carbon black series and outstanding comprehensive performance.
(3) The PTC core material of the graphene with the vertical orientation can reduce the resistance of the PTC and improve the long-term reliability, and the preparation method has the characteristics of simplicity, high efficiency and low cost.
Drawings
Fig. 1 is a schematic flow diagram of a process for preparing a PTC core with vertically oriented graphene in an exemplary embodiment of the present invention;
fig. 2 is a photograph of a PTC core with graphene oriented parallel to the film plane, wherein fig. 2A is a front view and fig. 2B is a side view, illustrating that a majority of graphene is oriented parallel to the film plane;
fig. 3 is a photograph of a PTC core with graphene oriented vertically along the plane of the film, fig. 3A is a front view and fig. 3B is a side view to illustrate that a majority of graphene is oriented perpendicular to the plane of the film;
fig. 4 is a graph showing the resistance-temperature characteristics of PTC products prepared in example 1 and comparative examples 1 and 2.
Detailed Description
The composite film of the graphene particles, the conductive filler and the high polymer material provided by the invention comprises oriented conductive networks formed by the graphene particles and the conductive filler, and is uniformly dispersed in a matrix material. The orientation network is realized by oriented graphene, and the graphene is connected through conductive particles.
Furthermore, the oriented graphene is perpendicular to the direction of the film, graphene, conductive particles and polymer composites with the graphene parallel to the direction of the film are required to be prepared, and sheets formed by the vertically oriented graphene, the conductive particles and the polymer composites with the graphene perpendicular to the direction of the film are prepared after stacking, melting and cutting.
The graphene, the conductive particles and the polymer material may be selected from, but not limited to, various materials described above, and will not be described here again.
Example 1
Referring to fig. 1, a PTC core material with vertically oriented graphene is prepared according to the following steps:
1 preparation of a composite Material of Vertically oriented graphene, carbon Black and polyethylene
1) Mixing 200 parts of polyethylene, 180 parts of carbon black and 20 parts of graphene in an internal mixer, setting the temperature to 200 ℃, mixing for 12min at the rotating speed of 80 r/min, and preparing a film with the thickness of 0.24-0.27 mm by an open mill, wherein the graphene is mostly oriented in parallel along the film plane;
2) Stacking a plurality of films in a metal die cavity with the thickness of 100 mm by 80mm, heating the films for 2 hours at 190 ℃ by a flat vulcanizing instrument, keeping the pressure at about 30Mpa, and then cooling the films to room temperature to take out the materials from the die cavity to obtain a blocky material with a graphene orientation structure;
3) Cutting the material into films with the thickness of 0.24-0.27 mm along the direction perpendicular to the stacked films by using diamond wires, wherein the orientation direction of graphene in the films is perpendicular to the film plane;
2, coating electrode plates on two surfaces of the film with the vertically oriented graphene through electroless copper plating and electrolytic copper plating, and punching the film into chips with the size of 5mm or 8mm by a sheet punching machine after 160kgy irradiation.
The ingredients and the electrical properties of the prepared PTC chip with the vertical orientation graphene structure are shown in Table 1, and the resistance is 0.1-0.2 omega. As shown by microscopic observation, a picture of the PTC core material with graphene oriented vertically along the film plane is shown in fig. 3, where fig. 3A is a front view and fig. 3B is a side view, illustrating that most of the graphene is oriented vertically to the film plane direction.
Comparative example 1
PTC chip of carbon black and polyethylene composite material:
unlike example 1, no graphene was added, and other materials and processing steps were the same as example 1, as a control group. The ingredients and the electrical properties of the prepared common PTC chip are shown in Table 1, and the resistance is 0.4-0.5 omega.
Comparative example 2
A PTC chip containing graphene has the same formula as that of the embodiment 1, but different preparation process, and comprises the following steps:
1) Mixing all the ingredients, and drawing the mixture into a graphene film which is oriented in parallel along the film through an open mill;
2) Directly plating copper and electroplating copper, coating electrode plates on two sides of the film, irradiating by 160kgy, and punching into chips with the size of 5mm or 8mm by a sheet punching machine.
The PTC ingredients and the electrical properties of the prepared graphene-based composite material with the parallel orientation are shown in Table 1, the resistance is 1.3-1.4 omega, and the vast majority of graphene is parallel oriented in the matrix along the plane of the film through observation of a microscope.
A picture of a PTC core with graphene oriented parallel to the film plane is shown in fig. 2, where fig. 2A is a front view and fig. 2B is a side view, illustrating that most of the graphene is oriented parallel to the film plane direction.
As can be seen from fig. 4, the PTC prepared in example 1 with vertically oriented graphene had the lowest initial resistance, the PTC prepared in comparative example 1 without added graphene had the next highest initial resistance, and the phenomenon explained by this was: the graphene belongs to a two-dimensional material, and the conductivity in a plane is far higher than that between planes, so that the graphene composite material oriented perpendicular to the film has high conductivity, and the prepared PTC initial resistance is low; however, when graphene is oriented in parallel along the composite sheet film, conduction of current along the upper and lower electrodes is hindered, so that the PTC initial resistance is higher than that without graphene.
The above description, illustration and examples are not intended to limit the design concept of the present invention, and the same person in the knowledge field of the present invention can modify the technical concept of the present invention in various forms, and such modifications and changes should also fall within the scope of the present invention.
Claims (10)
1. The conductive film based on the vertically oriented graphene takes a high molecular polymer as a matrix, and a conductive material is added into the high molecular polymer to form a film.
2. The vertically oriented graphene-based conductive film of claim 1, wherein: the radial dimension of the graphene is 10 nm-1 mm.
3. The vertically oriented graphene-based conductive film of claim 1, wherein: the conductive filler comprises one or more of graphite, conductive ceramic powder and metal powder, and is dispersed into a conductive network in the high polymer, and the communication among the graphene particles is realized.
4. A vertically oriented graphene-based conductive film according to any one of claims 1 to 3, wherein: comprising the following steps:
firstly, blending a high polymer with the content of 10-90 wt% and a conductive material containing 0.1-30 wt% of graphene particles, performing tape casting film forming, and performing hot pressing on a high polymer-based mixture to prepare a thin sheet with the thickness of 0.1-5 mm, wherein the graphene inside the thin sheet is parallel oriented along the plane of the thin film under the action of a flowing field;
secondly, stacking the thin sheets obtained in the first step, wherein the stacking number is 1-100, and hot pressing to obtain a polymer/graphene composite with a certain thickness and an orientation structure;
and thirdly, cutting the graphene into a film along a direction perpendicular to the orientation direction of the graphene, and obtaining the film with high conductivity in the orientation direction.
5. The vertically oriented graphene-based conductive film of claim 4, wherein: the orientation treatment mode in the first step also comprises one or more modes of electrostatic spinning, melt spinning, twin-screw extrusion, tape casting film forming, open mill film forming, spin coating, solution blending, layer-by-layer self-assembly and vacuum auxiliary forming.
6. Use of a vertically oriented graphene-based conductive film according to any one of claims 1 to 5 in PTC resistive products.
7. The use according to claim 6, characterized in that: the conductive film based on the vertical orientation graphene is used as a PTC core material, and the graphene particles are arranged in a specified direction to form an orientation network; the conductivity of the PTC polymer material core material in the specified direction is larger than that in other directions.
8. A PTC device of low resistance, characterized in that it is prepared by using the PTC polymeric material core material as claimed in claim 5 or 6, comprising the steps of: and (3) carrying out melt solidification on the core material obtained by stacking and carrying out tape casting or calendaring treatment, slicing from the vertical direction to form a graphene-based PTC core material which is vertically oriented along a plane, and coating electrode plates on two sides of the PTC core material.
9. A low resistance PTC element according to claim 8, wherein it is prepared by the steps of:
firstly, preparing a polymer-based mixture containing graphene particles into a thin sheet with the thickness of 0.1-5 mm through tape casting and hot pressing, wherein the graphene inside the thin sheet is parallel oriented along the plane of the thin film under the action of a flow field;
secondly, stacking the thin sheets obtained in the first step, and performing hot pressing to obtain a polymer/graphene composite with a certain thickness and an orientation structure;
thirdly, slicing along the direction perpendicular to the orientation direction of the graphene, wherein the film is used as a PTC high polymer material core material, and the orientation structures of the first step and the second step are reserved;
and fourthly, coating a metal foil electrode on the cutting surface to prepare the PTC product based on the graphene which is oriented vertically to the electrode plate as a conductive material.
10. A low resistance PTC element according to claim 8 or 9 wherein the slicing method comprises, but is not limited to, one or more of conventional mechanical cutting, diamond wire cutting, machine tool cutting, grinding and thinning.
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