A polymer conductive composite material and a PTC core material with positive temperature coefficient characteristics

Abstract

The present invention relates to the technical field of PTC core materials, and in particular to a polymer conductive composite material and a PTC core material with a positive temperature coefficient characteristic. The raw materials of the polymer conductive composite material include the following raw materials by weight: 4-15 parts of a polymer, 85-96 parts of a dopamine-modified conductive filler, and 0.02-0.5 parts of an antioxidant, and the stability of the conductive network is enhanced by coating and modifying the conductive filler with a dopamine active agent. The PTC core material with a positive temperature coefficient characteristic of the present invention has excellent resistance stability and higher voltage resistance.

Description

Technical Field

[0001] The invention relates to the technical field of PTC core materials, and in particular to a polymer conductive composite material and a PTC core material with positive temperature coefficient characteristics. Background Art

[0002] The resistivity of PTC materials increases with increasing temperature, especially when the temperature reaches near the melting point of the polymer, its resistivity will suddenly change and become approximately insulator. This phenomenon is called positive temperature coefficient effect (PTC), and this material is also called polymer PTC material. At present, PTC thermistors are made of one or more crystalline polymers and conductive fillers. The polymers are generally polyethylene, low-density polyethylene, high-density polyethylene, polyethylene graft polymers, polyvinylidene fluoride, etc. The conductive fillers are generally carbon black, metal powder or conductive ceramic powder.

[0003] Conductive ceramic powder has low resistivity and good oxidation resistance, and is currently widely used in PTC thermistor materials. Since the surface of conductive ceramic powder is relatively smooth and has no polar functional groups on the surface, it has poor adhesion to polymers. This makes the conductive network structure of the composite material very fragile, and after repeated use, the resistance value increases greatly, the performance is unstable, and the ability to withstand multiple impacts under high current is poor. In order to overcome these drawbacks, it is necessary to further improve the adhesion between polyethylene and conductive ceramic powder, effectively reduce the resistance value, and improve the stability of the conductive network structure. The current industry situation is that most of the silane coupling agents and phthalate coupling agents are directly added during the mixing process of conductive fillers and polymers. The disadvantage of this method is that the amount of coupling agent added accounts for a small proportion, and it is difficult to disperse evenly in the system; for conductive ceramic powders with regular and smooth surfaces, the coupling agent cannot form a stable and effective adhesion structure, so the effect of surface modification is greatly reduced. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a polymer conductive composite material and a PTC core material with positive temperature coefficient characteristics, which can not only increase the adhesion between the polymer and the conductive filler, but also improve the PTC strength and the stability of the PTC thermistor, thereby solving the problems in the prior art.

[0005] The technical solution of the present invention is:

[0006] The first aspect of the present invention provides a polymer conductive composite material, characterized in that the raw materials of the polymer conductive composite material include the following raw materials in parts by weight:

[0007] 4-15 parts of high molecular polymer;

[0008] 85-96 parts of dopamine modified conductive filler;

[0009] Antioxidant 0.02-0.5 parts.

[0010] The second aspect of the present invention provides a method for preparing a polymer conductive composite material, the preparation method comprising: uniformly mixing a polymer, a dopamine-modified conductive filler, and an antioxidant, plasticizing the mixture on an open mixing mill, and then pulling the mixture into a sheet to form the polymer conductive composite material.

[0011] The third aspect of the present invention provides the use of the polymer conductive composite material as described above in the present invention and / or the polymer conductive composite material prepared by the preparation method as described above in the present invention in a PTC core material.

[0012] A fourth aspect of the present invention provides a PTC core material with a positive temperature coefficient characteristic, comprising a polymer conductive composite material and metal foil electrodes provided on the upper and lower surfaces of the polymer conductive composite material.

[0013] The fifth aspect of the present invention provides a method for preparing a PTC core material with a positive temperature coefficient characteristic, the preparation method comprising: applying a layer of metal foil to the upper and lower surfaces of the polymer conductive composite material, respectively, and performing heat pressing to prepare a PTC core material with a positive temperature coefficient characteristic.

[0014] By adopting the above technical solution, the beneficial effects of the present invention are:

[0015] The polymer conductive composite material with a positive temperature coefficient of the present invention not only combines the polymer and the inorganic conductive filler more tightly through the dopamine activator, but also can significantly improve the high current impact resistance and stability of the core material.

[0016] The overcurrent protection element prepared by the dopamine-modified positive temperature coefficient polymer conductive composite material of the present invention should meet the requirements of low resistance at room temperature in actual application environment, and electrical characteristics such as cycle life, thermal shock and environmental aging tests must also be taken into consideration, so that the overcurrent protection element can still maintain stable PTC characteristics after experiencing multiple overcurrent or overtemperature conditions.

[0017] The dopamine-modified conductive composite material with a positive temperature coefficient can improve the molecular PTC thermistor's ability to withstand multiple large current shocks and its own stability. Another advantage of the present invention is that the experimental process is simple and the cycle is short, which greatly saves labor and raw material costs and achieves the effect of improving quality and reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the PTC element of the present invention.

[0019] Reference numerals:

[0020] 1-PTC components

[0021] 11- nickel electrode;

[0022] 12-metal copper foil;

[0023] 13-Polymer conductive composite materials DETAILED DESCRIPTION

[0024] Hereinafter, embodiments of a polymer conductive composite material and a PTC core material with positive temperature coefficient characteristics provided by the present invention will be described in detail.

[0025] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that a range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0026] After extensive research, the inventors of the present invention have found that the surface modifier of the dopamine system will undergo self-oxidative polymerization to form a self-polymer. The self-polymerization reaction can form a coating film similar to a natural adhesive on the surface of various materials, thereby modifying the smooth metal surface. The inventors have found that when the conductive filler is pretreated with a dopamine active agent, it can not only increase the adhesion between polyethylene and ceramic powder, improve the PTC strength and the stability of the PTC thermistor, but also show excellent electrical properties. On this basis, the present application has been completed.

[0027]

Polymer conductive composite materials

[0028] The present invention provides a polymer conductive composite material, wherein the polymer comprises a polymer, a dopamine modified conductive filler and an oxidant, wherein the conductive filler and the antioxidant are uniformly distributed in the polymer.

[0029] In the polymer conductive composite material provided by the present invention, the raw materials of the polymer conductive composite material include 4-15 parts by weight of the polymer. Optionally, the weight of the polymer is 4-8 parts, 8-10 parts, 10-15%, etc.

[0030] In some embodiments, the high molecular weight polymer is selected from one or more of polyethylene or a graft polymer of polyethylene.

[0031] Furthermore, the polyethylene may be, for example, high-density polyethylene, the melt index of the high-density polyethylene being 0.3 to 2.0 g / 10 min, optionally 0.3 to 1.2 g / 10 min or 1.2 to 2.0 g / 10 min. The melting point is 127 to 138° C., optionally 127 to 130° C. or 130 to 138° C. The density is 0.941 to 0.960. In a specific embodiment, for example, the high-density polyethylene is PetroChina Daqing 5000S, with a melt index of 1.2 g / 10 min; a melting point of about 130° C., and a density of 0.941 to 0.960.

[0032] Furthermore, the grafted polymer of polyethylene, for example, which can be purchased from HDPE E265, can improve the adhesion and compatibility between polar materials and non-polar materials.

[0033] In the polymer conductive composite material provided by the present invention, the raw materials of the polymer conductive composite material further include 85-96 parts by weight of dopamine modified conductive filler. Optionally, the weight of dopamine modified conductive filler is 85-90 parts, 90-96 parts, etc.

[0034] In some embodiments, the conductive filler in the dopamine-modified conductive filler is a conductive ceramic powder. Further, the conductive filler is selected from metal nitrides or carbides of Group IVB, VB, and VIB, and their solid solutions or mixtures. Optionally, the conductive filler is tungsten carbide. Preferably, the particle size of the tungsten carbide is 6-9um, for example, 6-7um, 7-9um, etc.

[0035] The dopamine in the dopamine-modified conductive filler is a dopamine-type active agent having many electrophilic functional groups in the molecule, such as phenols, aldehydes, amines, etc. Dopamine hydrochloride is preferred.

[0036] In the polymer conductive composite material provided by the present invention, the modification method of the dopamine modified conductive filler comprises: acidifying the conductive filler for pretreatment, adjusting the pH to alkaline, adding dopamine, stirring, washing and drying.

[0037] In the modification method of the dopamine-modified conductive filler, the acid used in the acidification may be, for example, acetic acid. The pretreatment time may be, for example, 20 to 40 minutes, and may be 20 to 30 minutes or 30 to 40 minutes.

[0038] In the modification method of the dopamine-modified conductive filler, the reagent for adjusting the pH to be alkaline may be, for example, hydroxymethylaminomethane.

[0039] In the modification method of the dopamine-modified conductive filler, the dopamine active agent undergoes a self-polymerization reaction under stirring conditions, and the stirring time is 2 to 24 hours, preferably 12 to 24 hours.

[0040] In some embodiments, the modification method of the dopamine-modified conductive filler includes:

[0041] 1) First, tungsten carbide powder is placed in water, and acetic acid is added thereto to adjust the pH to acidic, thereby performing acidification pretreatment of the conductive filler.

[0042] 2) Then, add an appropriate amount of hydroxymethylaminomethane to adjust the mixed solution to be alkaline. After the added hydroxymethylaminomethane is completely dissolved, weigh dopamine hydrochloride and pour it in to ensure that the concentration of the polymerization solution is 6-8g / L, and then self-polymerize under stirring conditions.

[0043] 3) After the self-polymerization is completed, the mixture is allowed to stand, the upper clear liquid is removed, and deionized water is added to the mixture for soaking. After the soaking, the conductive particles are suspended by stirring, filtered, washed, and dried overnight. Finally, the dried solid is ground to obtain a dopamine-modified conductive filler.

[0044] In one specific embodiment, the modification method of the dopamine-modified conductive filler includes:

[0045] 1) First, 300 g of tungsten carbide powder was weighed and placed in 150 ml of water, acetic acid was added dropwise to adjust the pH to acidic, and the conductive filler was acidified for 30 minutes.

[0046] 2) Then, add an appropriate amount of hydroxymethylaminomethane to adjust the mixed solution to be alkaline. After the added hydroxymethylaminomethane is completely dissolved, weigh dopamine hydrochloride and pour it in to ensure that the concentration of the polymerization solution is 6-8g / L, and then self-polymerize for 2h under stirring conditions.

[0047] 3) After the self-polymerization is completed, the mixture is allowed to stand for 20 minutes, the upper clear liquid is removed, and deionized water is added thereto to soak for 15 minutes. After the soaking, the conductive particles are suspended by stirring, and filtered and washed using a suction filter. The washing is repeated three times, and after washing, the mixture is placed in an oven at 70°C to dry overnight. Finally, the dried solid is ground to obtain a dopamine-modified conductive filler.

[0048] In the polymer conductive composite material provided by the present invention, the raw materials of the polymer conductive composite material further include 0.02-0.5 parts by weight of an antioxidant. Optionally, the weight of the antioxidant can be, for example, 0.02-0.1 parts, 0.1-0.3 parts, 0.3-0.5 parts, etc.

[0049] In some embodiments, the antioxidant is selected from one or more of antioxidant 1076, antioxidant 1010, antioxidant 168, and antioxidant 264. Multiple includes two or more.

[0050] In a specific embodiment, the raw materials of the polymer conductive composite material include the following raw materials in parts by weight:

[0051] 4-15 parts of high molecular polymer;

[0052] 85-96 parts of dopamine modified conductive filler;

[0053] Antioxidant 0.02-0.5 parts.

[0054]

Preparation method of polymer conductive composite material

[0055] The present invention also provides a method for preparing a polymer conductive composite material as described in the first aspect of the present invention, the preparation method comprising: uniformly mixing a polymer, a dopamine-modified conductive filler, and an antioxidant, plasticizing them on an open mixing mill, and then drawing a sheet to form the polymer conductive composite material.

[0056] In the preparation method of the polymer conductive composite material provided by the present invention, the dosage and specific selection of the polymer, dopamine modified conductive filler and antioxidant refer to those described in the first aspect of the present invention.

[0057] In the preparation method of the polymer conductive composite material provided by the present invention, the polymer, dopamine modified conductive filler, antioxidant, etc. are mixed at 150-180°C for 5-8 minutes, and the mixing speed is set at 60rpm; the temperature of the mixing mill is controlled not to be higher than the safe processing temperature, and then the material after the mixing is pulled into sheets of suitable size.

[0058]

use

[0059] The present invention also provides the use of the polymer conductive composite material according to the present invention and / or the polymer conductive composite material prepared according to the preparation method of the present invention in a PTC core material.

[0060] [PTC core material with positive temperature coefficient characteristics]

[0061] The present invention also provides a PTC core material with positive temperature coefficient characteristics, comprising a polymer conductive composite material and metal foil electrodes provided with upper and lower surfaces of the polymer conductive composite material. The polymer conductive composite material is a polymer conductive composite material prepared by the preparation method of the polymer conductive composite material described in the first aspect of the present invention and / or the polymer conductive composite material described in the second aspect of the present invention. The polymer conductive composite material can be, for example, a sheet-like polymer conductive composite material.

[0062] [Preparation method of PTC core material with positive temperature coefficient characteristics]

[0063] The present invention also provides a method for preparing a PTC core material with a positive temperature coefficient characteristic, the preparation method comprising: applying a layer of metal foil to the upper and lower surfaces of the polymer conductive composite material, respectively, and performing heat pressing to prepare the PTC core material with a positive temperature coefficient characteristic.

[0064] In the method for preparing the PTC core material with positive temperature coefficient characteristics provided by the present invention, the metal foil may be, for example, a metal copper foil, and more preferably, a nickel-plated roughened copper foil.

[0065] In the preparation method of the PTC core material with positive temperature coefficient characteristics provided by the present invention, the core material is placed in a flat vulcanizing machine for hot pressing.

[0066] In a specific embodiment, a layer of metal copper foil is placed on the upper and lower parts of the polymer conductive composite material, and a layer of buffer plastic layer is placed on the upper and lower parts of the metal copper foil. The five layers in the middle are pressed together with a steel plate, and the steel plate, the pressed buffer plastic layer, the metal copper foil and the polymer conductive composite material sheet are symmetrically covered in sequence to form a multi-layer structure. The sheeting operation is performed by a hot press at a temperature of, for example, 180°C, and after the hot pressing is completed, the sheet is cooled by a cold press to obtain a PTC core material with a positive temperature coefficient characteristic.

[0067] The dopamine-modified positive temperature coefficient PTC core material of the present invention can be used to prepare an overcurrent protection element PTC thermistor. The pressed PTC core material is punched into chips of different specifications and sizes according to different use requirements, and pins are welded on both sides to obtain a dopamine-modified overcurrent protection PTC thermistor.

[0068] The beneficial effects of the present invention are further illustrated below in conjunction with embodiments.

[0069] In order to make the invention purpose, technical scheme and beneficial technical effect of the present invention clearer, the present invention is further described in detail below in conjunction with examples. However, it should be understood that the examples of the present invention are only for explaining the present invention, not for limiting the present invention, and the examples of the present invention are not limited to the examples given in the specification. The specific experimental conditions or operating conditions not specified in the examples are made under conventional conditions, or are made under the conditions recommended by the material supplier.

[0070] In addition, it should be understood that one or more method steps mentioned in the present invention do not exclude the existence of other method steps before or after the combination step or the insertion of other method steps between these explicitly mentioned steps, unless otherwise specified; it should also be understood that the combination connection relationship between one or more devices / apparatuses mentioned in the present invention does not exclude the existence of other devices / apparatuses before or after the combination device / apparatus or the insertion of other devices / apparatuses between these explicitly mentioned two devices / apparatuses, unless otherwise specified. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or the scope of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the present invention without substantially changing the technical content.

[0071] In the following examples, unless otherwise specified, various raw materials of the present invention can be purchased from the market or prepared according to conventional methods in the art.

[0072] The ingredients used in the following comparative examples or embodiments are shown in Table 1:

[0073] Table 1

[0074]

[0075] Comparative Example 1

[0076] The comparative formula is shown in Table 2. The temperature of the open mill is set at 170°C. A certain amount of high-density polyethylene, grafted high-density polyethylene, tungsten carbide, and antioxidant are added according to the formula ratio. The mixing speed is set at 60 rpm. After 8 minutes of open mixing, the sheet is pulled into a 5 cm*20 cm sheet to form a polymer conductive composite material with a positive temperature coefficient.

[0077] like Figure 1, place a layer of metal copper foil 12 on the upper and lower parts of the above-mentioned polymer conductive composite material 13, and then place a layer of buffer plastic on the upper and lower parts of the metal copper foil 12, and use a steel plate to press the five layers of materials in the middle up and down, and symmetrically cover the steel plate, the special buffer material for pressing, the metal copper foil and the material sheet in sequence to form a multi-layer structure. Pre-press for 1.5 minutes, the pre-pressing operation pressure is 0-5MPa, and the temperature is 180℃. Then press at 5MPa pressure for 1.5 minutes and 180℃. Subsequently, increase the operating pressure to 10MPa, the temperature is 180℃, and the time is 3 minutes. After the pressing is completed, deflate 3 times, and then press for 6 minutes under the same conditions. Finally, transfer to a cold press machine for 10MPa and 6 minutes of cold pressing. Use a mold to punch out a 3mm*4mm positive temperature coefficient PTC chip, and weld a nickel sheet 11 as an electrode on the upper and lower surfaces of the chip to form a PTC element.

[0078] Comparative Example 2

[0079] The comparative formula is shown in Table 2. The temperature of the open mill is set at 170°C. A certain amount of high-density polyethylene, grafted high-density polyethylene, KH-570 modified tungsten carbide, and antioxidant are added according to the formula ratio. The mixing speed is set at 60 rpm. After 8 minutes of open mixing, it is pulled into a 5 cm*20 cm sheet to form a conductive composite material with a positive temperature coefficient.

[0080] Place a layer of metal copper foil on the upper and lower parts of the above materials, and then place a layer of buffer plastic on the upper and lower parts of the metal copper foil. Use a steel plate to press the five layers of materials in the middle up and down, and symmetrically cover the steel plate, the special buffer material for pressing, the metal copper foil and the material sheet in sequence to form a multi-layer structure. Pre-press for 1.5 minutes, the pre-pressing operation pressure is 0-5MPa, and the temperature is 180℃. Then press at 5MPa pressure for 1.5 minutes and 180℃. Subsequently, increase the operating pressure to 10MPa, the temperature is 180℃, and the time is 3 minutes. After the pressing is completed, deflate 3 times, and then press for 6 minutes under the same conditions. Finally, transfer to a cold press machine for 10MPa and 6 minutes of cold pressing. Use a mold to punch out a 3mm*4mm positive temperature coefficient PTC chip, and weld a nickel sheet as an electrode on the upper and lower surfaces of the chip to form a PTC element 1.

[0081] Example 1

[0082] The steps for preparing the positive temperature coefficient element are the same as those of Comparative Example 2, except that the conductive filler 3 modified with dopamine for 2h is used. The electrical properties of the positive temperature coefficient element are shown in Table 2.

[0083] Example 2

[0084] The steps for preparing the positive temperature coefficient element are the same as those of Comparative Example 2, except that the conductive filler 3 modified with dopamine for 8h is used. The electrical properties of the positive temperature coefficient element are shown in Table 2.

[0085] Example 3

[0086] The steps for preparing the positive temperature coefficient element are the same as those of Comparative Example 2, except that the conductive filler 3 modified with dopamine for 24 hours is used. The electrical properties of the positive temperature coefficient element are shown in Table 2.

[0087] The resistance of this component is measured using the micro-resistance four-wire method, and the measurement results are shown in Table 2:

[0088] Table 2

[0089]

[0090] 1) Cycle life: The ratio of the resistance of a PTC component to its initial resistance when the voltage / current value is 8V / 50A, the power is on for 6s and the power is off for 60s, and the impact is repeated 1000 times.

[0091] 2) Withstand voltage: The ratio of the resistance of the PTC component to the initial resistance after it is powered on for 24 hours under the conditions of voltage / current value of 8V / 50A.

[0092] 3) Withstand voltage level: Under the initial condition of voltage / current value of 8V / 50A, the voltage of PTC component is increased by 1V per minute until the PTC component is broken down and burned. The limit value of withstand voltage of the test component is tested.

[0093] In summary, the present invention effectively overcomes various shortcomings of the prior art and has high industrial utilization value.

[0094] The above is only a preferred embodiment of the present invention, and is not any formal or substantial limitation of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present invention, and these improvements and supplements should also be regarded as the protection scope of the present invention. Any technician familiar with this profession, without departing from the spirit and scope of the present invention, can make some changes, modifications and evolutions of the technical content disclosed above, which are equivalent embodiments of the present invention; at the same time, any changes, modifications and evolutions of any equivalent changes made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A polymer conductive composite material, characterized in that: The raw materials of the polymer conductive composite material include the following raw materials in parts by weight: 4-15 parts of high molecular polymer; 85-96 parts of dopamine modified conductive filler; Antioxidant 0.02-0.5 parts.

2. The polymer conductive composite material according to claim 1, characterized in that: The high molecular polymer is selected from one or more of polyethylene or polyethylene graft polymers.

3. The polymer conductive composite material according to claim 2, characterized in that: The polyethylene is high-density polyethylene, and the high-density polyethylene has a melt index of 0.3-2.0 g / 10 min, a melting point of 127-138° C., and a density of 0.941-0.

960.

4. The polymer conductive composite material according to claim 1, characterized in that: Also includes any one or more of the following features: A1) the conductive filler in the dopamine modified conductive filler is conductive ceramic powder; A2) the dopamine in the dopamine-modified conductive filler is dopamine hydrochloride; A3) The modification method of the dopamine-modified conductive filler comprises: acidifying the conductive filler for pretreatment, adjusting the pH to alkaline, adding dopamine, stirring, washing and drying; A4) The antioxidant is selected from one or more of antioxidant 1076, antioxidant 1010, antioxidant 168, and antioxidant 264.

5. The polymer conductive composite material according to claim 4, characterized in that: Also includes any one or more of the following features: A11) the conductive filler is selected from metal nitrides or carbides of Group IVB, VB, and VIB, and solid solutions or mixtures thereof; A31) In the modification method of the dopamine-modified conductive filler, the acid used in the acidification is acetic acid; A32) In the modification method of the dopamine-modified conductive filler, the pretreatment time is 20 to 40 minutes; A33) In the modification method of the dopamine-modified conductive filler, the reagent for adjusting the pH to alkaline is hydroxymethylaminomethane; A34) In the modification method of the dopamine-modified conductive filler, the stirring time is 2 to 24 hours.

6. The polymer conductive composite material according to claim 5, characterized in that: Also includes any one or more of the following features: A111) The conductive filler is tungsten carbide, and preferably, the particle size of the tungsten carbide is 6-9 um; A341) In the modification method of the dopamine-modified conductive filler, the stirring time is 12 to 24 hours.

7. The method for preparing a polymer conductive composite material according to any one of claims 1 to 6, characterized in that: The preparation method comprises: uniformly mixing a high molecular polymer, a dopamine modified conductive filler and an antioxidant, plasticizing the mixture on an open mill, and then drawing the mixture into a high molecular conductive composite material.

8. Use of the polymer conductive composite material according to any one of claims 1 to 6 and / or the polymer conductive composite material prepared according to the preparation method according to claim 7 in PTC core materials.

9. A PTC core material having a positive temperature coefficient characteristic, characterized in that: It comprises a polymer conductive composite material and metal foil electrodes provided with upper and lower surfaces of the polymer conductive composite material; Wherein, the polymer conductive composite material is the polymer conductive composite material according to any one of claims 1 to 6 and / or the polymer conductive composite material prepared by the preparation method according to claim 7.

10. The method for preparing a PTC core material having a positive temperature coefficient characteristic according to claim 9, characterized in that: The preparation method comprises: applying a layer of metal foil to the upper and lower surfaces of the polymer conductive composite material respectively, and performing heat pressing to prepare a PTC core material with positive temperature coefficient characteristics.

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