Polymer PTC (Positive Temperature Coefficient) composite material and production method thereof
By adding carbon black and modified carbon nanotubes to the high-density polyvinyl matrix, polymer PTC composite materials were prepared, which solved the problems of uneven distribution of conductive fillers and insufficient matrix performance, and achieved efficient heat resistance and mechanical performance improvement of the material.
Patent Information
- Application Number
- CN202510389797.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-31
- Publication Date
- 2025-05-30
AI Technical Summary
The conductive fillers of existing polymer PTC composite materials are unevenly distributed, and migration or agglomeration may occur, resulting in unstable local conductive paths and affecting the overall performance. At the same time, the mechanical strength and heat resistance of the matrix are poor.
High-density polyethylene is used as the matrix, carbon black and modified carbon nanotubes are added as conductive materials, and the mixture is prepared by ultrasonic dispersion and oven drying, and kneading is carried out in a double-roller mixer to further enhance the mechanical and heat resistance of the material.
The stable and efficient heat resistance and mechanical properties of polymer PTC composite materials are achieved, which avoids the problem of instability of conductive paths and improves the long-term stability of the material.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of PTC materials, and specifically relates to a polymer PTC composite material and a production method thereof. Background Art
[0002] With the continuous development of science and technology, polymer materials are increasingly widely used in modern industry. Especially in the fields of electronics, communication, energy, and automotive, polymer materials have become one of the indispensable basic materials with their excellent properties and diverse functions. Among them, polymer composite materials with positive temperature coefficient (PTC) characteristics have attracted much attention in the applications such as overcurrent protection, self-limiting heaters, and intelligent sensors due to their unique electrothermal properties.
[0003] The PTC effect refers to the phenomenon that the resistivity of some materials increases significantly with the increase of temperature. When the ambient temperature or working current causes the internal temperature of the materials to rise, their resistance will increase rapidly, thereby restricting the current passing through. This characteristic enables PTC materials to achieve the functions of automatically regulating current, preventing overload or short circuit. For polymer PTC composite materials, their core structure is usually formed by dispersing conductive fillers in a polymer matrix. Common polymer matrices include polyethylene (PE), polypropylene (PP), etc., and carbon black, graphene, metal powders, or conductive ceramic particles are often used as conductive fillers.
[0004] In the normal working state, the conductive networks of these composite materials remain continuous and exhibit low resistance; but when the temperature exceeds a certain critical value (i.e., the Curie point), due to the thermal expansion coefficient of the polymer matrix being much larger than that of the conductive filler, the contact area between conductive particles decreases or even breaks, resulting in a sharp increase in resistance, thus playing a protective role. This characteristic not only improves the safety and reliability of equipment but also reduces the dependence on external control systems.
[0005] Although polymer PTC composite materials have been widely used, the existing technologies still face some challenges. For example, the distribution of conductive fillers in most current polymer PTC composite materials is uneven, and migration or agglomeration may occur, which easily causes unstable local conduction paths and thus affects the overall performance. In addition, the matrices of PTC composite materials are all organic polymer materials, and their mechanical strength and heat resistance are poor. They are prone to aging under high-temperature conditions, which will further reduce their mechanical strength. Therefore, based on the above background, the market urgently needs a polymer PTC composite material with both high heat resistance and mechanical properties to meet the higher requirements in the technical field of PTC materials. Summary of the Invention
[0006] The object of the present invention is to overcome the defects of the prior art and provide a polymer PTC composite material and a production method thereof.
[0007] The object of the present invention can be achieved by the following technical solutions:
[0008] A production method of a polymer PTC composite material includes the following steps:
[0009] A1. Add carbon black, nano-silica, coupling agent and antioxidant into an ethanol solution, then ultrasonically disperse for 10 - 20 min, and dry in an oven to obtain a mixture.
[0010] A2. Add high-density polyethylene and modified carbon nanotubes into a two-roll mill, mix for 10 - 20 min, then add the mixture prepared in step A1, and continue to mix for 20 - 30 min. After mixing is completed, press into sheets, discharge, cool, and cut to obtain the polymer PTC composite material.
[0011] Further, each raw material is as follows by weight parts: 8 - 12 parts of carbon black, 6 - 10 parts of nano-silica, 3 - 6 parts of coupling agent, 5 - 7 parts of antioxidant, 93 - 105 parts of high-density polyethylene, 13 - 25 parts of modified carbon nanotubes.
[0012] Further, the coupling agent is a silane coupling agent.
[0013] Further, the antioxidant is a hindered phenol antioxidant.
[0014] Using high-density polyethylene as the matrix endows the material with certain mechanical properties. Adding nano-silica as a filler further enhances the mechanical properties of the material. The added carbon black can not only be used as one of the conductive fillers, but also enhance the thermal stability and certain mechanical properties of the material.
[0015] Further, the modified carbon nanotubes are prepared through the following steps:
[0016] Step 1. Add cyanuric chloride and acetone into a three-necked flask equipped with a magnetic stirrer, reflux condenser and thermometer. Then mix sulfanilic acid and a sodium carbonate solution (mass fraction 18%), stir until the solid is completely dissolved, and then drop it into the three-necked flask, stir rapidly. After dropping is completed, control the reaction temperature at 60 °C and reflux for 2 h. After the reaction is completed, adjust the pH = 7 with a sodium carbonate solution, filter by suction, and dry to obtain intermediate product 1. The dosage ratio of cyanuric chloride, acetone, sulfanilic acid, and sodium carbonate solution is 19.1 g:100 mL:34.6 g:100 mL;
[0017] Cyanuric chloride undergoes a nucleophilic substitution reaction with sulfanilic acid. Sodium carbonate is used as an acid-binding agent to remove the hydrogen chloride generated during the reaction and catalyze the reaction. By adjusting the molar ratio of cyanuric chloride to sulfanilic acid to be close to 1:2 (cyanuric chloride is slightly in excess), it can be ensured that only two chlorine atoms in the cyanuric chloride molecule undergo substitution reactions, thereby generating intermediate 1. The specific reaction process is as follows:
[0018]
[0019] Step 2: Add intermediate 1, sodium carbonate, 2,3-diaminonaphthalene, and N,N-dimethylformamide into a three-necked flask equipped with a magnetic stirrer, a condenser, and a thermometer. Introduce nitrogen as a protective gas, set the reaction temperature at 65 °C, and stir the reaction for 5 h. After the reaction is completed, remove part of the solvent by vacuum distillation, and then purify it by silica gel column chromatography (the eluent is benzene and ethyl acetate, and their volume ratio is 5:2). Rotate and evaporate to remove the eluent to obtain intermediate 2. The dosage ratio of intermediate 1, sodium carbonate, 2,3-diaminonaphthalene, and N,N-dimethylformamide is 49.9 g: 13.8 g: 17.3 g: 150 mL;
[0020] Intermediate 1 undergoes a nucleophilic substitution reaction with 2,3-diaminonaphthalene. Sodium carbonate is used as an acid-binding agent to remove the hydrogen chloride generated during the reaction and catalyze the reaction. By adjusting the molar ratio of intermediate 1 to 2,3-diaminonaphthalene to be close to 1:1 (2,3-diaminonaphthalene is slightly in excess), it can be ensured that only one amino group in the 2,3-diaminonaphthalene molecule undergoes a substitution reaction, thereby generating intermediate 2. The specific reaction process is as follows:
[0021]
[0022] Step 3: Mix carboxylated carbon nanotubes and N,N-dimethylformamide, and ultrasonically treat to make the carboxylated carbon nanotubes uniformly dispersed. Then add intermediate 2 and dicyclohexylcarbodiimide, and magnetically stir for 30 min. Then, under the water bath condition at 55 °C, keep warm for 4 h. Then remove the water bath and magnetically stir at room temperature for 8 h. After the reaction is completed, perform suction filtration. The filter residue is washed with anhydrous ethanol multiple times, dried, ground, and modified carbon nanotubes are obtained. The dosage ratio of carboxylated carbon nanotubes, N,N-dimethylformamide, intermediate 2, and dicyclohexylcarbodiimide is 1 g: 100 mL: 13.5 g: 5.1 g;
[0023] Under the action of dicyclohexylcarbodiimide, the -COOH on the surface of the carboxylated carbon nanotubes undergoes an amidation reaction with the amino group on intermediate 2, grafting organic molecules on the surface of the carbon nanotubes to obtain modified carbon nanotubes.
[0024] Carbon nanotubes are a kind of conductive material, and have excellent heat resistance and mechanical properties. By grafting organic molecular chains on the surface of carbon nanotubes, a large number of hydrophobic groups are contained in the organic molecular chains, which can enhance the interfacial compatibility between carbon nanotubes and the polyethylene matrix, thus promoting the dispersion of carbon nanotubes and greatly reducing the agglomeration phenomenon of carbon nanotubes. In addition, the grafted organic molecular chains contain a variety of functional groups, among which the sulfonic acid group has a relatively high bond energy and can enhance the thermal stability of the matrix. In addition, benzene rings and naphthalene rings are introduced. Benzene rings and naphthalene rings belong to aryl groups, and the π-π conjugate system in aromatic compounds has relatively high thermal stability, which can effectively disperse heat. Moreover, compared with benzene rings, naphthalene rings have higher rigidity and thermal stability, further improving the thermal stability and mechanical properties of the matrix. Finally, the organic molecular chains are connected to the inorganic carbon nanotubes, making the organic molecules not easy to migrate and exude, improving the stability of the organic molecular chains and making the properties of the modified carbon nanotubes more durable.
[0025] Further, the carboxylated carbon nanotubes are prepared by the following steps:
[0026] Mix the carbon nanotubes and the mixed acid, place them in an ice-water bath at 5°C, ultrasonically treat for 15 min, then add them to a three-necked flask equipped with a magnetic stirrer, a reflux condenser and a thermometer. Under magnetic stirring, maintain the temperature at 75°C and reflux and heat for 6 h. After the reaction is completed, cool to room temperature, add to ice water and let it stand for precipitation, centrifuge and wash, and dry to obtain carboxylated carbon nanotubes.
[0027] Further, the mixed acid is obtained by mixing concentrated sulfuric acid with a mass fraction of 98% and concentrated nitric acid with a mass fraction of 65% in a volume ratio of 3:1.
[0028] Further, the dosage ratio of the carbon nanotubes to the mixed acid is 1 g:40 mL.
[0029] The beneficial effects of the present invention:
[0030] The PTC composite material prepared by the present invention uses high-density polyethylene as the polymer matrix, and adds carbon black and modified carbon nanotubes as conductive materials;
[0031] 1. Using high-density polyethylene as the matrix endows the material with certain mechanical properties;
[0032] 2. Adding nano-silica to the raw materials further enhances the mechanical properties of the material;
[0033] 3. Carbon black can not only further enhance the mechanical properties of the material, but also enhance the heat resistance of the material;
[0034] 4. By modifying carbon nanotubes, compared with ordinary carbon nanotubes, they have better hydrophobicity, are not prone to agglomeration in the matrix, have better dispersibility, greatly enhance the heat resistance and mechanical properties of the material, and the properties are long-term stable.
[0035] In summary, the PTC composite material prepared by the present invention has stable and efficient heat resistance and mechanical properties, and has important application value in the technical field of PTC materials. Specific Embodiments
[0036] The following will combine the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.
[0037] Example 1
[0038] Prepare carboxylated carbon nanotubes:
[0039] Mix 1 g of carbon nanotubes with 40 mL of a mixed acid (30 mL of concentrated sulfuric acid with a mass fraction of 98% and 10 mL of concentrated nitric acid with a mass fraction of 65%), place it in an ice-water bath at 5 °C, ultrasonically treat for 15 min, then add it to a three-necked flask equipped with a magnetic stirrer, reflux condenser and thermometer. Under magnetic stirring, maintain the temperature at 75 °C, reflux and heat for 6 h. After the reaction is completed, cool to room temperature, add it to ice water for static precipitation, centrifuge and wash, and dry to obtain carboxylated carbon nanotubes.
[0040] Example 2
[0041] Prepare modified carbon nanotubes:
[0042] Step 1. Add 19.1 g of cyanuric chloride and 100 mL of acetone to a three-necked flask equipped with a magnetic stirrer, reflux condenser and thermometer. Then mix 34.6 g of sulfanilic acid and 100 mL of sodium carbonate solution (mass fraction 18%), stir until the solid is completely dissolved, and then drop it into the three-necked flask. Stir rapidly. After the dropping is completed, control the reaction temperature at 60 °C and reflux for 2 h. After the reaction is completed, adjust the pH = 7 with sodium carbonate solution, filter by suction, and dry to obtain Intermediate Product 1;
[0043] Step 2: Add 49.9 g of intermediate 1, 13.8 g of sodium carbonate, 17.3 g of 2,3-diaminonaphthalene, and 150 mL of N,N-dimethylformamide into a three-necked flask equipped with a magnetic stirrer, a condenser, and a thermometer. Introduce nitrogen as a protective gas, set the reaction temperature at 65 °C, stir and react for 5 h. After the reaction is completed, remove part of the solvent by vacuum distillation, and then purify by silica gel column chromatography (the eluent is benzene and ethyl acetate, and the volume ratio of the two is 5:2). Rotate and evaporate to remove the eluent to obtain intermediate 2;
[0044] Step 3: Mix 1 g of the carboxylated carbon nanotubes prepared in Example 1 with 100 mL of N,N-dimethylformamide, and ultrasonically treat to make the carboxylated carbon nanotubes uniformly dispersed. Then add 13.5 g of intermediate 2 and 5.1 g of dicyclohexylcarbodiimide, magnetically stir for 30 min, and then keep warm at 55 °C in a water bath for 4 h. Then remove the water bath and magnetically stir at room temperature for 8 h. After the reaction is completed, perform suction filtration. Wash the filter residue with absolute ethanol for multiple times, dry, and grind to obtain the modified carbon nanotubes.
[0045] Example 3
[0046] Preparation of modified carbon nanotubes:
[0047] Step 1: Add 38.2 g of cyanuric chloride and 200 mL of acetone into a three-necked flask equipped with a magnetic stirrer, a reflux condenser, and a thermometer. Then mix 69.2 g of sulfanilic acid and 200 mL of sodium carbonate solution (mass fraction 18%), stir until the solid is completely dissolved, and then drop it into the three-necked flask. Stir rapidly. After the dropping is completed, control the reaction temperature at 60 °C and reflux for 2 h. After the reaction is completed, adjust the pH = 7 with sodium carbonate solution, perform suction filtration, and dry to obtain intermediate 1;
[0048] Step 2: Add 99.8 g of intermediate 1, 27.6 g of sodium carbonate, 34.6 g of 2,3-diaminonaphthalene, and 300 mL of N,N-dimethylformamide into a three-necked flask equipped with a magnetic stirrer, a condenser, and a thermometer. Introduce nitrogen as a protective gas, set the reaction temperature at 65 °C, stir and react for 5 h. After the reaction is completed, remove part of the solvent by vacuum distillation, and then purify by silica gel column chromatography (the eluent is benzene and ethyl acetate, and the volume ratio of the two is 5:2). Rotate and evaporate to remove the eluent to obtain intermediate 2;
[0049] Step 3: Mix 2 g of the carboxylated carbon nanotubes prepared in Example 1 with 200 mL of N,N-dimethylformamide, and perform ultrasonic treatment to uniformly disperse the carboxylated carbon nanotubes. Then add 27 g of Intermediate 2 and 10.2 g of dicyclohexylcarbodiimide, and magnetically stir for 30 min. Then, under the water bath condition at 55 °C, keep warm for 4 h, and then remove the water bath and magnetically stir at room temperature for 8 h. After the reaction is completed, perform suction filtration, wash the filter residue with absolute ethanol for multiple times, dry, and grind to obtain modified carbon nanotubes.
[0050] Example 4
[0051] A1: Add 8 g of carbon black, 6 g of nano-silica, 3 g of silane coupling agent KH-550, and 5 g of antioxidant 1010 to 100 mL of ethanol solution, then perform ultrasonic dispersion for 10 min, and dry in an oven to obtain a mixed material;
[0052] A2: Add 93 g of high-density polyethylene and 13 g of the modified carbon nanotubes prepared in Example 2 to a two-roll mill, mix for 10 min, then add the mixed material prepared in Step A1, and continue to mix for 20 min. After the mixing is completed, perform sheet pressing, discharging, cooling, and cutting to obtain a polymer PTC composite material.
[0053] Example 5
[0054] A1: Add 10 g of carbon black, 8 g of nano-silica, 5 g of silane coupling agent KH-550, and 6 g of antioxidant 1010 to 100 mL of ethanol solution, then perform ultrasonic dispersion for 20 min, and dry in an oven to obtain a mixed material;
[0055] A2: Add 99 g of high-density polyethylene and 19 g of the modified carbon nanotubes prepared in Example 3 to a two-roll mill, mix for 20 min, then add the mixed material prepared in Step A1, and continue to mix for 30 min. After the mixing is completed, perform sheet pressing, discharging, cooling, and cutting to obtain a polymer PTC composite material.
[0056] Example 6
[0057] A1: Add 12 g of carbon black, 10 g of nano-silica, 6 g of silane coupling agent KH-550, and 7 g of antioxidant 1010 to 100 mL of ethanol solution, then perform ultrasonic dispersion for 20 min, and dry in an oven to obtain a mixed material;
[0058] A2: Add 105 g of high-density polyethylene and 25 g of the modified carbon nanotubes prepared in Example 3 to a two-roll mill, mix for 20 min, then add the mixed material prepared in Step A1, and continue to mix for 30 min. After the mixing is completed, perform sheet pressing, discharging, cooling, and cutting to obtain a polymer PTC composite material.
[0059] Comparative Example 1
[0060] Replace the modified carbon nanotubes in Example 6 with ordinary carbon nanotubes of the same quality, and the remaining steps are the same as those in Example 6 to obtain the material.
[0061] Comparative Example 2
[0062] Use commercially available PTC materials.
[0063] Perform the following performance tests on Examples 4, 5, 6 and Comparative Examples 1 and 2 according to different test standards:
[0064] Use the national standard GB / T 1040.2-2006 "Determination of Tensile Properties of Plastics - Part 2: Test Conditions for Moulded and Extruded Plastics" to determine the tensile properties;
[0065] Perform two thermal cycle treatments on the specimen. Specifically, heat the material from room temperature to 160 °C within 5 minutes, and then cool it to room temperature by air cooling. Determine the tensile strength after the thermal cycle treatment (GB / T 1040.2-2006), and calculate the retention rate of the tensile strength; the retention rate of the tensile strength = tensile strength after testing / tensile strength before testing × 100%;
[0066] The measured results are shown in the following table:
[0067]
[0068] As can be seen from the above table, the PTC composite materials prepared in the embodiments of the present invention have higher heat resistance and mechanical properties than the comparative examples. Moreover, in Examples 4, 5, and 6, as the amount of modified carbon nanotubes increases, the mechanical properties and heat resistance of the materials are enhanced. In summary, the present invention has important application value in the technical field of PTC materials.
[0069] In the description of the specification, the description referring to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.
[0070] The above content is only an example and illustration of the present invention. Those skilled in the art of the present technology can make various modifications or supplements to the described specific embodiments or use similar methods for substitution, as long as they do not deviate from the invention or exceed the scope defined by the claims of the present invention, they should all fall within the protection scope of the present invention.
Claims
1. A method for producing a polymer PTC composite material, characterized in that: The following steps are involved: A1. Add carbon black, nano-silica, coupling agent and antioxidant into ethanol solution, then disperse by ultrasonic for 10-20 min, and dry in oven to obtain a mixture; A2. Add high-density polyethylene and modified carbon nanotubes to a double-roll mill, mix for 10-20 minutes, then add the mixture prepared in step A1, and continue mixing for 20-30 minutes. After mixing is completed, the mixture is pressed, discharged, cooled, and cut to obtain a polymer PTC composite material.
2. The method for producing a polymer PTC composite material according to claim 1, characterized in that: The modified carbon nanotubes are prepared by the following steps: Step 1, add cyanuric chloride and acetone into a flask, then mix p-aminobenzenesulfonic acid and sodium carbonate solution, stir until the solid is completely dissolved, then dropwise add into the flask, stir rapidly, after the dropwise addition is completed, reflux at 60° C. for 2 h, after the reaction is completed, adjust the pH to 7, filter, and dry to obtain intermediate 1; Step 2, add the intermediate product 1, sodium carbonate, 2,3-diaminonaphthalene and N,N-dimethylformamide into a flask, introduce nitrogen, stir and react at 65° C. for 5 h. After the reaction is completed, distill under reduced pressure, purify by column chromatography, and rotary evaporate to obtain the intermediate product 2; Step 3: mix the carboxylated carbon nanotubes and N,N-dimethylformamide, perform ultrasonic treatment to evenly disperse the carboxylated carbon nanotubes, then add the intermediate 2 and dicyclohexylcarbodiimide, stir magnetically for 30 minutes, keep warm at 55°C for 4 hours, and then stir at room temperature for 8 hours. After the reaction is completed, filter, wash, dry and grind to obtain modified carbon nanotubes.
3. The method for producing a polymer PTC composite material according to claim 2, characterized in that: In step 1, the ratio of cyanuric chloride, acetone, p-aminobenzenesulfonic acid and sodium carbonate solution is 19.1 g:100 mL:34.6 g:100 mL.
4. The method for producing a polymer PTC composite material according to claim 2, characterized in that: In step 2, the ratio of the amount of intermediate product 1, sodium carbonate, 2,3-diaminonaphthalene and N,N-dimethylformamide is 49.9 g:13.8 g:17.3 g:150 mL.
5. The method for producing a polymer PTC composite material according to claim 2, characterized in that: In step 3, the ratio of the amount of carboxylated carbon nanotubes, N,N-dimethylformamide, intermediate 2, and dicyclohexylcarbodiimide is 1 g:100 mL:13.5 g:5.1 g.
6. The method for producing a polymer PTC composite material according to claim 1, characterized in that: The raw materials are calculated in parts by weight as follows: 8-12 parts of carbon black, 6-10 parts of nano-silicon dioxide, 3-6 parts of coupling agent, 5-7 parts of antioxidant, 93-105 parts of high-density polyethylene, and 13-25 parts of modified carbon nanotubes.
7. The method for producing a polymer PTC composite material according to claim 1, characterized in that: The coupling agent is a silane coupling agent.
8. The method for producing a polymer PTC composite material according to claim 1, characterized in that: The antioxidant is a hindered phenol antioxidant.
9. A polymer PTC composite material, characterized in that: Produced according to the method according to any one of claims 1 to 8.