WO2020034979A1 - Polymer-based conductive composite material and overcurrent protection element - Google Patents

Abstract

A polymer-based conductive composite material and an overcurrent protection element prepared therefrom. The polymer-based conductive composite material comprises an insulating polymer substrate and two conductive fillers dispersed in the polymer substrate. The polymer substrate accounts for 20% - 75% of the volume fraction of the polymer-based conductive composite material. The two conductive fillers account for 25% - 85% of the volume fraction of polymer-based conductive composite material. The two conductive fillers both have outstanding weather resistance and excellent conductivity. One of conductive fillers has self-lubricating properties and is easy to process and produce. The overcurrent protection element prepared by using said conductive composite material has a "sandwich" structure, a composite material being used as the core material, the upper and lower sides of the core material being covered with metal electrode foils, the conductive composite core material and the metal electrode foil being tightly bonded. Such kind of overcurrent protection element has low electrical resistance, excellent environmental resistance and reliability and good processability.

Description

Polymer-based conductive composite material and overcurrent protection element Technical field

The invention relates to a polymer-based conductive composite material and an overcurrent protection element, in particular to a polymer-based conductive composite material with low room temperature resistance, excellent environmental resistance and good processability, and a product prepared therefrom. Overcurrent protection element.

Background technique

An overcurrent protection element made of a polymer-based conductive composite material can maintain a low resistance value at room temperature or lower. Because the conductive composite material has a positive temperature coefficient effect, when an overcurrent or overtemperature phenomenon occurs in a circuit, Its resistance will instantly increase to a high resistance value, so that the circuit is in an open state to achieve the purpose of protecting circuit components. Therefore, the polymer-based conductive composite material can be connected to the circuit as the core material of an overcurrent or temperature sensing element. Such materials have been widely used in electronic circuit protection components.

The polymer-based conductive composite material is generally composed of a polymer and a conductive filler, and the conductive filler is uniformly distributed in the polymer substrate on a macroscopic basis. The polymers are generally crystalline polyolefins and copolymers thereof, such as polyethylene or ethylene-propylene copolymers. Carbon black, metal powder or conductive ceramic powder conductive fillers are generally used. Carbon black cannot meet the requirements of low resistance of electronic circuits because of its high specific resistance. The conductive composite material prepared with metal powder as the conductive filler has extremely low resistance, but because the metal powder is susceptible to oxidation, the conductive composite material needs to be encapsulated to prevent the resistance of the metal powder from being increased in the air due to oxidation. On the one hand, the size of the encapsulated overcurrent protection element cannot be effectively reduced, and it is difficult to meet the requirements for miniaturization of electronic components. On the other hand, higher requirements are placed on the encapsulation material and the encapsulation process. In order to achieve low resistance and high environmental reliability, metal carbide, metal nitride, or metal boride ceramic powder (such as titanium carbide) is gradually used as the conductive filler of low-resistance polymer-based conductive composite materials in the industry. Materials have come a long way. However, due to the high hardness of metal carbides, metal nitrides or metal borides, a series of problems (such as severe wear of mechanical parts and high processing costs) have occurred during the production and processing process. The area of the overcurrent protection element is further reduced (such as 1210, 1206, 0805, 0603 and other sizes), and it becomes more and more obvious. The new ternary Mn + 1AXn phase filler is found late, the molding process is complicated, the industrialization level is low, and its price is relatively expensive. Using it as a conductive filler will greatly increase the manufacturing cost of the enterprise. Therefore, it is necessary to develop a conductive composite material with low resistance, excellent environmental reliability, good processability and relatively low cost.

Summary of the Invention

An object of the present invention is to provide a polymer-based conductive composite material.

Yet another object of the present invention is to provide an overcurrent protection element prepared from the polymer-based conductive composite material. The overcurrent protection element has low cost, low resistance, excellent environmental reliability, and good processing performance.

To achieve the above object, the present invention discloses a polymer-based conductive composite material, including:

A polymer substrate, which accounts for 20% to 75% of the volume fraction of the polymer-based conductive composite material;

The first conductive filler is a solid solution, which accounts for 10% to 80% of the volume fraction of the conductive composite material, has a particle size of 0.1 μm to 10 μm, and has a volume resistivity not greater than 200 μΩ · cm. The conductive filler is dispersed Among the polymers, the solid solution is a combination of one or two or more of a metal boride, a metal nitride, a metal carbide, or a metal silicide.

The second conductive filler is a conductive filler having a layered structure, and has a particle diameter of 0.1 μm to 20 μm, a particle size distribution range of 0.01 μm to 100 μm, and a volume resistivity of less than 1 × 10-3 Ω · cm, which accounts for the high 2% to 50% of the volume fraction of the molecular-based conductive composite material is dispersed in the polymer substrate. The molecular formula of the conductive filler having a layered structure in Ω · cm is: Mn + 1AXn, where:

M element is one of transition metal elements Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta;

Element A is one of Group IIIA, Group IVA, Group VA or Group VIA elements Al, Si, P, S, Ga, Ge, As, Cd, In, Sn, Tl, Pb;

Element X is a carbon or nitrogen element; 1 ≦ n ≦ 3 and is an integer.

The polymer substrate is: polyethylene, chlorinated polyethylene, oxidized polyethylene, polyvinyl chloride, butadiene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer, polystyrene, Polycarbonate, polyamide, polyethylene terephthalate, polybutylene terephthalate, polyphenylene ether, polyphenylene sulfide, polyformaldehyde, phenolic resin, polytetrafluoroethylene, tetrafluoroethylene -Hexafluoropropylene copolymer, polytrifluoroethylene, polyvinyl fluoride, maleic anhydride grafted polyethylene, polypropylene, polyvinylidene fluoride, epoxy resin, ethylene-vinyl acetate copolymer, polymethyl methacrylate, One of ethylene-acrylic acid copolymers and mixtures thereof. Among them, polyethylene includes: high density polyethylene, low density polyethylene, ultra low density polyethylene, linear low density polyethylene, ultra high molecular weight polyethylene, and the like.

The volume fraction of the polymer substrate in the conductive composite material is between 20% and 75%, preferably between 25% and 70%, and more preferably between 30% and 65%.

The conductive filler having a layered structure of _{Sc 2 InC, Ti 2 AlC,} Ti 2 GaC, Ti 2 InC, Ti 2 TlC, V 2 AlC, V 2 GaC, Cr 2 GaC, Ti 2 AlN, Ti 2 GaN, Ti ₂ InN, V ₂ GaN, Cr ₂ GaN, Ti ₂ GeC, Ti ₂ SnC, Ti ₂ PbC, V ₂ GeC, Cr ₂ SiC, Cr ₂ GeC, V ₂ PC, V ₂ AsC, Ti ₂ SC, Zr _{2 InC, Zr 2 TlC, Nb 2} AlC, Nb 2 GaC, Nb 2 InC, Mo 2 GaC, Zr 2 InN, Zr 2 TlN, Zr 2 SnC, Zr 2 PbC, Nb 2 SnC, Nb 2 PC, Nb 2 AsC, Zr ₂ SC, Nb ₂ SC, Hf ₂ SC, Hf ₂ InC, Hf ₂ TlC, Ta ₂ AlC, Ta ₂ GaC, Hf ₂ SnC, Hf ₂ PbC, Hf ₂ SnN, Ti ₃ AlC ₂ , V ₃ AlC ₂ , Ta ₃ AlC ₂ , Ti ₃ SiC ₂ , Ti ₃ GeC ₂ , Ti ₃ SnC ₂ , Ti ₄ AlN ₃ , V ₄ AlC ₃ , Ti ₄ GaC ₃ , Nb ₄ AlN ₃ , Ta ₄ AlC ₃ , Ti ₄ SiC ₃ , One or a mixture of two or more of Ti ₄ GeC ₃ .

The average particle diameter of the conductive filler having a layered structure is 0.01 μm to 100 μm, preferably 0.05 μm to 50 μm, and more preferably 0.1 μm to 20 μm.

The volume resistivity of the conductive filler having a layered structure is less than 1 × 10 ^-3 Ω · cm, more preferably less than 5 × 10 ^-3 Ω · cm, and most preferably less than 1 × 10 ^-2 Ω · cm.

The volume fraction of the conductive filler having a layered structure in the polymer-based conductive composite material is between 2% and 50%, preferably between 4% and 45%, and more preferably between 6% and 40%. between.

The metal boride is tantalum boride, tantalum diboride, vanadium boride, vanadium diboride, zirconium diboride, titanium diboride, niobium boride, niobium diboride, dimolybdenum boride, pentaboron At least one of dimolybdenum disulfide, hafnium diboride, ditungsten boride, tungsten boride, dichromium boride, chromium boride, chromium diboride, or pentachrome triboride.

The metal nitride is at least one of tantalum nitride, vanadium nitride, zirconium nitride, titanium nitride, niobium nitride, or hafnium nitride.

The carbide is one of tantalum carbide, vanadium carbide, zirconium carbide, titanium carbide, niobium carbide, dimolybdenum carbide, hafnium carbide, tungsten carbide, ditungsten carbide, or trichromium dicarbonide.

The metal silicides are tantalum disilicide, pentatan trisilicide, trivanadium silicide, vanadium disilicide, zirconium disilicide, titanium disilicide, pentasilium trisiliconide, niobium disilicide, molybdenum disilicide, hafnium disilicide, disilicide At least one of tungsten, trichrome silicide or chromium disilicide.

The polymer-based conductive composite material may contain other additive components, such as an antioxidant, a radiation crosslinking agent (commonly referred to as a radiation accelerator, a crosslinking agent, or a crosslinking accelerator, such as triallyl isocyanurate Esters), coupling agents, dispersants, stabilizers, non-conductive fillers (such as magnesium hydroxide, calcium carbonate), flame retardants, arc inhibitors, or other components. These components usually account for at most 15%, such as 10% by volume, of the total volume of the polymer-based conductive composite material.

The overcurrent protection element prepared by using the above-mentioned polymer-based conductive composite material is covered with a metal electrode foil on each of the upper and lower sides of the core material of the conductive composite material, and the metal electrode foil is tightly combined with the polymer-based conductive composite material layer.

The volume resistivity of the overcurrent protection element is less than 0.02Ω · cm at 25 ° C, and it has outstanding weather resistance and good processability.

The polymer-based conductive composite material of the present invention and the overcurrent protection element prepared from the polymer-based conductive composite material can be prepared as follows:

The polymer base material and the conductive filler are put into a mixing device at a mixing ratio, and melt-mixed at a temperature higher than the melting point of the polymer base material. The mixing equipment may be an internal mixer, an open mill, a single-screw extruder, or a twin-screw extruder. Then, the melted and mixed polymer conductive composite material is processed into a sheet material through extrusion molding, compression molding or calendar molding. Generally, the thickness of the conductive composite sheet is 0.01-3.0 mm, preferably 0.05-2.0 mm, and more preferably 0.1-1.0 mm for the convenience of processing.

The method for forming the core material composite sheet of the overcurrent protection element is to composite metal electrode foils on both sides of the polymer-based conductive composite sheet, and the method of composite metal electrode foils on both sides of the conductive composite sheet includes molding composite or conductive composite material from After the sheet extrusion die is extruded and in a molten state, the electrode foil is directly pressed together by a roller. The composite sheet can be processed into surface-mount overcurrent protection components through a series of PCB processes such as etching, lamination, drilling, immersion copper, tin plating and dicing. It can also be cut into a single chip and connected with Other metal parts are machined into SMT or Strap-type overcurrent protection elements. The method of dividing the core material composite sheet of the overcurrent protection element into a single chiplet includes any method of separating the single element from the composite product, such as die cutting, etching, scribing, and laser cutting. The single chiplet has a planar shape, that is, there are two surfaces perpendicular to the current flowing direction, and the distance between the two surfaces is relatively small, that is, at most 3.0 mm, preferably at most 2.0 mm, and particularly preferably at most 1.0mm, for example 0.5mm. The single chiplet may be of any shape, such as a rectangle, a triangle, a circle, a rectangle, a ring, a polygon, or other irregular shapes. The metal electrode foil is tightly combined with the polymer-based conductive composite material layer. The thickness of the metal electrode foil is generally at most 0.2 mm, preferably at most 0.1 mm, especially at most 0.08 mm, for example, 0.035 mm. Suitable materials for metal electrode foils include nickel, copper, aluminum, zinc, and composites thereof, such as copper foil, nickel foil, single-sided nickel-plated copper foil, double-sided nickel-plated copper foil, and the like.

Other metal parts can be connected to the metal electrode foil by one or a combination of spot welding, laser welding, reflow soldering, electroplating, chemical deposition, spray coating, sputtering, or a conductive adhesive, thereby connecting overcurrent protection. Into the circuit. The term "metal part" includes any structural part that can communicate with the metal electrode foil, and it can be of any shape, for example, dot-shaped, linear, ribbon-shaped, lamellar, cylindrical, full-round through-hole, semi-circular through-hole, arc Through holes, blind holes, other irregular shapes, and combinations thereof. The substrate of the "metal part" can be any metal and alloy capable of conducting electricity, such as nickel, copper, aluminum, zinc, tin, bismuth, indium, silver, gold, and alloys thereof.

Generally, the stability of the performance of the overcurrent protection element can be improved by means of crosslinking and / or heat treatment. Cross-linking can be chemical cross-linking or radiation cross-linking, for example, it can be achieved using a cross-linking accelerator, electron beam irradiation or Co ⁶⁰ irradiation. The radiation dose required by the overcurrent protection element is generally less than 1000 kGy, preferably 1-500 kGy, and more preferably 1-200 kGy. The heat treatment may be annealing, thermal cycling, and high and low temperature alternation, for example, + 85 ° C / -40 ° C high and low temperature alternation. The temperature environment of the annealing may be any temperature below the decomposition temperature of the polymer substrate, such as a high temperature annealing above the melting temperature of the polymer substrate and a low temperature annealing below the melting temperature of the polymer substrate.

The resistance of the overcurrent protection element of the present invention at 25 ° C is less than 0.1Ω · cm, preferably less than 0.05Ω · cm, and most preferably less than 0.02Ω · cm. Therefore, the resistance of the overcurrent protection element of the present invention at 25 ° C Very low, for example 1.0mΩ-20mΩ.

The advantages of the invention are that the polymer-based conductive composite material has low resistivity, excellent weather resistance, easy processing, and relatively low cost. The overcurrent protection element prepared from the polymer-based conductive composite material has a low room temperature resistivity, excellent weather resistance, and low processing cost.

BRIEF DESCRIPTION OF THE DRAWINGS

1 is a schematic structural diagram of an overcurrent protection element according to the present invention;

FIG. 2 is a schematic structural diagram of an overcurrent protection component with pins prepared in Embodiment 1 of the present invention.

detailed description

The present invention will be further described in detail through specific examples.

Example 1

The composition of the conductive composite material for preparing the overcurrent protection element is shown in Table 1. The polymer is high-density polyethylene with a melting temperature of 131 ° C, a density of 0.954g / cm ³ , and an added content of 50%; the first conductive filler is solid solution titanium carbide TiC, with an average particle diameter of 2.5um, and the added amount is 44%; the second conductive filler is Ti3AlC2 with a layered structure, the average particle diameter is 2.0 μm, and the added amount is 6%. The preparation process of the overcurrent protection element is as follows: set the temperature of the mixer to 180 ° C and the rotation speed to 30 rpm, add the polymer for 3 minutes, and then add the conductive filler to continue the mixer for 15 minutes to obtain the polymer. Based conductive composites. The melt-mixed polymer-based conductive composite material is rolled through an open mill to obtain a polymer-based conductive composite material 11 having a thickness of 0.20-0.25 mm.

FIG. 1 is a schematic structural diagram of an overcurrent protection element according to the present invention. A layer of polymer-based conductive composite material 11 is placed between two metal electrode foils 12 symmetrical to each other. The metal electrode foil 12 and the polymer-based conductive composite material layer 11 are tight. Combined. The polymer-based conductive composite material 11 and the metal electrode foil 12 are tightly bonded together by a thermocompression bonding method. The temperature of thermocompression is 180 ° C. Preheat for 5 minutes, then press for 3 minutes at a pressure of 5 MPa, then press for 10 minutes at a pressure of 12 MPa, and then cold press for 8 minutes on a cold press. Die-cut into a single component of 3 * 4mm, and finally, two metal pins 13 (shown in FIG. 2) are connected to the surfaces of two metal electrode foils 12 by reflow soldering to form an overcurrent protection component.

Example 2

The steps for preparing the polymer-based conductive composite material and the overcurrent protection element are the same as those in Example 1, but the volume fraction of the first conductive filler solid solution TiC was changed from 44% to 38%, and the volume fraction of the second conductive filler Ti3AlC2 was changed from 6 % Becomes 12%. The formula of the polymer-based conductive composite material of this embodiment and the electrical characteristics of the overcurrent protection element are shown in Table 1.

Example 3

The steps for preparing the polymer-based conductive composite material and the overcurrent protection element are the same as in Example 1, but the volume fraction of the first conductive filler solid solution TiC is changed from 44% to 32%, and the volume fraction of the second conductive filler Ti3AlC2 is changed from 6 % Becomes 18%. The formula of the polymer-based conductive composite material of this embodiment and the electrical characteristics of the overcurrent protection element are shown in Table 1.

Example 4

The steps for preparing the polymer-based conductive composite material and the overcurrent protection element are the same as those in Example 1, but the volume fraction of the first conductive filler solid solution TiC was changed from 44% to 26%, and the volume fraction of the second conductive filler Ti3AlC2 was changed from 6 % Becomes 24%. The formula of the polymer-based conductive composite material of this embodiment and the electrical characteristics of the overcurrent protection element are shown in Table 1.

Example 5

The steps for preparing the polymer-based conductive composite material and the overcurrent protection element are the same as in Example 1, but the volume fraction of the first conductive filler solid solution TiC is changed from 44% to 20%, and the volume fraction of the second conductive filler Ti3AlC2 is changed from 6 % Becomes 30%. The formula of the polymer-based conductive composite material of this embodiment and the electrical characteristics of the overcurrent protection element are shown in Table 1. Comparative Example

The steps of the polymer-based conductive composite material and the overcurrent protection element prepared in the comparative example are the same as in Example 1, but the volume fraction of the first conductive filler solid solution TiC is changed from 44% to 50%, and the volume of the second conductive filler Ti3AlC2 is changed. The score changed from 6% to 0%, that is, the addition of the second conductive filler was eliminated. The formula of the polymer-based conductive composite material of this comparative example and the electrical characteristics of the overcurrent protection element are shown in Table 1.

Table 1 shows the comparison between the torque and the host current when the rotor speed is fixed during the processing of the hybrid device by the polymer-based conductive composite of the present invention, and the temperature at 25 ° C after the overcurrent protection element is triggered under the condition of 6V / 50A. Resistance value after 1 hour in the environment. In Table 1, R represents the resistance of the overcurrent protection element chip, that is, the surface of the conductive composite material covered with the metal electrode foil 12; R0 represents the resistance after the two electrode pins 12 are welded on the surface of the two electrode foils 12 of the overcurrent protection element ; R1 represents the resistance value measured after the overcurrent protection element is continuously energized (6V / 50A) for 6 seconds and placed in a 25 ° C temperature environment for 1 hour; R100 represents the overcurrent protection element is continuously energized (6V / 50A) 6 After 60 seconds, power off for 60 seconds, and then cycle 100 times, and then measure the resistance value after standing for 1 hour at 25 ° C. High temperature and high humidity (High temperature and humidity) R1000h indicates the resistance value measured after the overcurrent protection element is placed in an environment of 85 ° C and 85% RH for 1000 hours, and then placed in a temperature environment of 25 ° C for 1 hour. Heat shock (Rock Shock) R100 means that the overcurrent protection element is stored for 1hr in + 85 ° C environment, and converted to -40 ° C environment for 1hr in 5min. This cycle is repeated 100 times, and then placed in 25 ° C temperature environment for 1 hour The measured resistance value.

Table 1

It can be seen from Table 1 that the resistance of the overcurrent protection element in Examples 1-5 is less than 20 milliohms. After 100 times of current shock, high temperature, high humidity, and temperature shock environment experiments, the resistance change of the overcurrent protection element is relatively Small, lower than conventional non-second conductive filler formulation systems. The polymer-based conductive composite material used in the overcurrent protection element of the present invention contains a second conductive filler with a low resistivity and a layered structure, and the self-lubricating property of the second conductive filler. Both the torque and the host current are lower than the conductive composite material of a single conductive filler system, which shows that the new system has excellent processing performance, at the same time has lower room temperature resistivity, excellent weather resistance, and does not need to be encapsulated to protect the polymer Based on the conductive composite material, over-current protection elements with a thickness of 0.2mm-2.0mm and a current carrying area of 1210, 1206, 0805, 0603, etc. can be prepared.

The content and features of the present invention have been disclosed as above, however, the present invention described above only briefly or only relates to a specific part of the present invention, and the features of the present invention may be more than what is disclosed herein. Therefore, the protection scope of the present invention should not be limited to the content disclosed in the embodiments, but should include the combination of all the content embodied in different parts, as well as various substitutions and modifications that do not depart from the present invention, and are the rights of the present invention. Covered by the request.

Claims (8)

1. A polymer-based conductive composite material characterized in that it comprises:

   A polymer substrate, which accounts for 20% to 75% of the volume fraction of the polymer-based conductive composite material;

   The first conductive filler is a solid solution, which accounts for 10% to 80% of the volume fraction of the conductive composite material, has a particle size of 0.1 μm to 10 μm, and has a volume resistivity not greater than 200 μΩ · cm. The conductive filler is dispersed In the polymer substrate; the solid solution is a combination of one or two or more of metal boride, metal nitride, metal carbide or metal silicide;

   The second conductive filler is a conductive filler having a layered structure, and has a particle diameter of 0.1 μm to 20 μm, a particle size distribution range of 0.01 μm to 100 μm, and a volume resistivity of less than 1 × 10-3 Ω · cm, which accounts for the high 2% to 50% of the volume fraction of the molecular-based conductive composite material is dispersed in the polymer substrate; the molecular formula of the conductive filler having a layered structure is: M _{n + 1} AX _n , where:

   M element is one of transition metal elements Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta;

   Element A is one of Group IIIA, Group IVA, Group VA or Group VIA elements Al, Si, P, S, Ga, Ge, As, Cd, In, Sn, Tl, Pb;

   Element X is a carbon or nitrogen element; 1 ≦ n ≦ 3 and is an integer.
2. The polymer-based conductive composite material according to claim 1, wherein the polymer base material is: polyethylene, chlorinated polyethylene, oxidized polyethylene, polyvinyl chloride, butadiene-acrylonitrile copolymer , Acrylonitrile-butadiene-styrene copolymer, polystyrene, polycarbonate, polyamide, polyethylene terephthalate, polybutylene terephthalate, polyphenylene ether, polybenzene Sulfide, polyformaldehyde, phenolic resin, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, polytrifluoroethylene, polyfluoroethylene, maleic anhydride grafted polyethylene, polypropylene, polyvinylidene fluoride, ring One or a mixture of two or more of oxyresin, ethylene-vinyl acetate copolymer, polymethyl methacrylate, and ethylene-acrylic acid copolymer.
3. The polymer-based conductive composite material according to claim 1, wherein the metal boride is tantalum boride, tantalum diboride, vanadium boride, vanadium diboride, zirconium diboride, or diboride Titanium, niobium boride, niobium diboride, dimolybdenum boride, dimolybdenum pentaboride, hafnium diboride, tungsten diboride, tungsten boride, dichromium boride, chromium boride, chromium diboride or At least one of pentachrome triboride.
4. The polymer-based conductive composite material according to claim 1, wherein the metal nitride is at least one of tantalum nitride, vanadium nitride, zirconium nitride, titanium nitride, niobium nitride, or hafnium nitride. One.
5. The polymer-based conductive composite material according to claim 1, wherein the carbide is tantalum carbide, vanadium carbide, zirconium carbide, titanium carbide, niobium carbide, molybdenum carbide, hafnium carbide, tungsten carbide, tungsten carbide, or dicarbide One of three chromium.
6. The polymer-based conductive composite material according to claim 1, wherein the metal silicide is tantalum disilicide, pentatanium trisilicide, trivanadium silicide, vanadium disilicide, zirconium disilicide, titanium disilicide, At least one of pentatitanium silicide, niobium disilicide, molybdenum disilicide, hafnium disilicide, tungsten disilicide, trichrome silicide, or chromium disilicide.
7. The polymer-based conductive composite material according to claim 1, wherein said electrically conductive filler having a layered structure of _{Sc 2 InC, Ti 2 AlC,} Ti 2 GaC, Ti 2 InC, Ti 2 TlC, V 2 AlC, V ₂ GaC, Cr ₂ GaC, Ti ₂ AlN, Ti ₂ GaN, Ti ₂ InN, V ₂ GaN, Cr ₂ GaN, Ti ₂ GeC, Ti ₂ SnC, Ti ₂ PbC, V ₂ GeC, Cr ₂ SiC, _{cr 2 GeC, V 2 PC,} V 2 AsC, Ti 2 SC, Zr 2 InC, Zr 2 TlC, Nb 2 AlC, Nb 2 GaC, Nb 2 InC, Mo 2 GaC, Zr 2 InN, Zr 2 TlN, Zr 2 _{SnC, Zr 2 PbC, Nb 2} SnC, Nb 2 PC, Nb 2 AsC, Zr 2 SC, Nb 2 SC, Hf 2 SC, Hf 2 InC, Hf 2 TlC, Ta 2 AlC, Ta 2 GaC, Hf 2 SnC, Hf ₂ PbC, Hf ₂ SnN, Ti ₃ AlC ₂ , V ₃ AlC ₂ , Ta ₃ AlC ₂ , Ti ₃ SiC ₂ , Ti ₃ GeC ₂ , Ti ₃ SnC ₂ , Ti ₄ AlN ₃ , V ₄ AlC ₃ , Ti ₄ One or a mixture of two or more of GaC ₃ , Nb ₄ AlN ₃ , Ta ₄ AlC ₃ , Ti ₄ SiC ₃ , and Ti ₄ GeC ₃ .
8. An overcurrent protection element, comprising a polymer-based conductive composite material layer according to any one of claims 1 to 7 sandwiched between two metal electrode foils, the metal electrode foil and the polymer-based foil The conductive composite material layers are tightly compounded.

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