Modified multi-walled carbon nanotube, preparation method thereof and conductive polypropylene composite material containing modified multi-walled carbon nanotube

Abstract

The invention discloses a modified multi-walled carbon nanotube, a preparation method thereof and a conductive polypropylene composite material containing the modified multi-walled carbon nanotube, and the preparation method of the modified multi-walled carbon nanotube comprises the following steps: S1, taking lauryl sodium sulfate, adding the lauryl sodium sulfate into water, and fully dissolving to prepare a lauryl sodium sulfate solution with the concentration of 3-5mmol / L; s2, adding a multi-walled carbon nanotube into the solution, and stirring for 5-6 hours; s3, adding a pyrrole monomer into the mixed solution in the step S2, and stirring for 1-3 hours; and then adding an initiator ammonium persulfate into the solution, and carrying out stirring reaction at 20-30 DEG C for 4-6 hours to prepare the polypyrrole-coated multi-walled carbon nanotube. The prepared modified multi-walled carbon nanotube has an excellent coating effect, and the dispersing performance and the conductivity of the modified multi-walled carbon nanotube in a polypropylene material can be improved, so that the conductive polypropylene composite material is endowed with a stable and excellent conductive effect under the condition that the addition amount is reduced, and the modified multi-walled carbon nanotube has practical application significance.

Description

Technical Field

[0001] The present application belongs to the technical field of preparation of functional fillers of polymer materials, and specifically relates to a modified multi-walled carbon nanotube and a preparation method thereof, and also relates to the application of the modified multi-walled carbon nanotube in a conductive polypropylene composite material. Background Art

[0002] Multi-walled carbon nanotubes (MWCNTs) are a tubular structure formed by nesting multiple layers of graphene, with a diameter usually between 2 and 100 nm. This special tubular structure gives multi-walled carbon nanotubes higher strength and stability. The inner layer usually acts as a metal, while the outer layer can be a metal or a semiconductor. It is precisely because of the unique physical, chemical and electrical properties of multi-walled carbon nanotubes that they are widely used in electronic devices, material reinforcement, nanosensors and other fields. They are often used as functional fillers added to polymer matrices to enhance their strength and durability, and to improve the electrical or thermal conductivity of polymers and other properties.

[0003] Taking polypropylene as an example, the introduction of multi-walled carbon nanotubes can significantly reduce the surface resistance of polypropylene composite materials, thereby improving their electrical conductivity. However, there are also certain defects in adding multi-walled carbon nanotubes to the polypropylene system: on the one hand, multi-walled carbon nanotubes are easy to aggregate, affecting their uniformity in the composite material, and thus affecting the improvement of its electrical conductivity; on the other hand, the current processing of polypropylene materials is mainly based on twin-screw extrusion technology, and multi-walled carbon nanotubes are due to the strong interaction between the tubes in the structure and the high flexibility of the molecular chain of polypropylene. Specifically, multi-walled carbon nanotubes are materials formed by staggered graphene sheets curled around the central axis at a certain spiral angle, which has strong rigidity itself, which is quite different from the flexible chain segment of polypropylene, resulting in difficulty in obtaining uniform modified materials through ordinary twin-screw shear dispersion during polypropylene processing. It is necessary to increase the amount of multi-walled carbon nanotubes added to achieve a better stable electrical conductivity effect, which undoubtedly increases the cost of the material.

[0004] Therefore, there is an urgent need to find a multi-walled carbon nanotube with excellent performance, which can be added to a polypropylene system to obtain a polypropylene composite material with stable and excellent conductive properties with a relatively low addition amount and a conventional twin-screw processing technology. Summary of the invention

[0005] In view of this, the primary purpose of the present application is to provide a method for preparing modified multi-walled carbon nanotubes. Through the preparation method of the present application, pyrrole is polymerized on the surface of the multi-walled carbon nanotubes, so that polypyrrole is coated on the surface of the multi-walled carbon nanotubes to obtain modified multi-walled carbon nanotubes with good coating effect and good dispersion effect, which not only improves the dispersion performance of the multi-walled carbon nanotubes in the polypropylene material, but also the polypyrrole and the multi-walled carbon nanotubes work synergistically to give the conductive polypropylene composite material stable and excellent conductive properties.

[0006] In order to achieve the above objectives, this application adopts the following technical solutions:

[0007] One aspect of the present application provides a method for preparing modified multi-walled carbon nanotubes, comprising the following steps:

[0008] S1. Take sodium dodecyl sulfate and add it into water to fully dissolve it to prepare a sodium dodecyl sulfate solution with a concentration of 3 to 5 mmol / L;

[0009] S2, adding multi-walled carbon nanotubes to the above solution and stirring for 5 to 6 hours;

[0010] S3, adding pyrrole monomer to the mixed solution of step S2 and stirring for 1 to 3 hours; then adding initiator ammonium persulfate to the above solution, stirring and reacting at 20 to 30° C. for 4 to 6 hours to obtain polypyrrole-coated multi-walled carbon nanotubes.

[0011] Another aspect of the present application provides a modified multi-walled carbon nanotube, which is prepared by the preparation method described above.

[0012] Another aspect of the present application provides a conductive polypropylene composite material, the raw material components of which include the modified multi-walled carbon nanotubes described above.

[0013] Another aspect of the present application provides a method for preparing the conductive polypropylene composite material as described above, comprising the following steps:

[0014] Polypropylene, modified multi-walled carbon nanotubes, antioxidants and processing aids are weighed according to the mass ratio, mixed evenly, and then added into a twin-screw extruder through a main feeding port for extrusion processing to obtain a conductive polypropylene composite material.

[0015] Beneficial effects of this application:

[0016] The present application controls the reaction conditions, the selection of the reaction raw materials, etc., so that the pyrrole monomer undergoes polymerization reaction on the surface of the multi-walled carbon nanotube, thereby preparing the multi-walled carbon nanotube with the surface coated with polypyrrole, and the coating effect of the modified multi-walled carbon nanotube obtained by the present application is good, and has excellent dispersion effect. Since polypyrrole is a conductive polymer, therefore, it can synergize with the multi-walled carbon nanotube, so that the conductive polypropylene composite material has better stable and excellent electrical conductivity. In addition, since the surface is coated with polypyrrole, the surface polarity of the carbon nanotube material can be reduced, so that the agglomeration of the multi-walled carbon nanotube can be prevented, therefore, the obtained polypyrrole-coated multi-walled carbon nanotube has better excellent dispersion performance in the polypropylene system, can be less added, can obtain stable and excellent electrical conductivity, reduce the comprehensive cost of the material, has important significance. DETAILED DESCRIPTION

[0017] The following will clearly and completely describe the implementation methods of the present application. The technical solutions in the implementation methods described below are exemplary and are only possible technical implementations of the present application, not all possible implementations. Those skilled in the art can fully combine the implementation methods of the present application to obtain other implementation methods without creative work, and these implementation methods are also within the scope of protection of the present application.

[0018] The first aspect of the present application discloses a method for preparing modified multi-walled carbon nanotubes, comprising the following steps:

[0019] S1. Take sodium dodecyl sulfate and add it into water to fully dissolve it to prepare a sodium dodecyl sulfate solution with a concentration of 3 to 5 mmol / L;

[0020] S2, adding multi-walled carbon nanotubes to the above solution and stirring for 5 to 6 hours;

[0021] S3, adding pyrrole monomer to the mixed solution of step S2 and stirring for 1 to 3 hours; then adding initiator ammonium persulfate to the above solution, stirring and reacting at 20 to 30° C. for 4 to 6 hours to obtain polypyrrole-coated multi-walled carbon nanotubes.

[0022] The preparation method of the present application can prepare modified multi-walled carbon nanotubes with good coating effect and excellent dispersion effect. Due to the coating of polypyrrole, it can use its property of being a conductive polymer to cooperate with multi-walled carbon nanotubes, thereby more effectively improving the conductivity. In addition, the surface-coated polypyrrole reduces the polarity of the multi-walled carbon nanotubes, improves the dispersion performance of the modified multi-walled carbon nanotubes in the polypropylene matrix, and can better improve the conductivity.

[0023] In the present application, the specific amount of each reaction raw material can be optimized and determined by experiments, so there is no special restriction. In some specific embodiments of the present application, for every 1g of multi-walled carbon nanotubes, there is 100-200mL of sodium dodecyl sulfate solution, 0.5-0.7mL of pyrrole monomer, and 1.5-2g of initiator ammonium persulfate. For example, for 1g of multi-walled carbon nanotubes, the volume of sodium dodecyl sulfate solution can be any volume of 100mL, 110mL, 120mL, 150mL, 180mL or 200mL; the amount of pyrrole monomer can be any volume of 0.5mL, 0.55mL, 0.6mL, 0.65mL or 0.7mL; the initiator ammonium persulfate can be any mass of 1.5g, 1.55g, 1.6g, 1.7g, 1.8g, 1.9g or 2g.

[0024] In the present application, there is no special requirement for the multi-walled carbon nanotubes. Multi-walled carbon nanotubes of common specifications or types in the art can be used. In some specific embodiments of the present application, the multi-walled carbon nanotubes have a diameter of 8 to 60 nm and a length of 20 to 100 μm.

[0025] In addition, it is understood that in step S3, after the reaction is completed, the steps of filtering, washing and drying are also included, and these steps are conventional steps in the art, so there is no particular limitation. In some specific embodiments of the present application, the number of washing times is 3 to 5 times, and the drying is drying at 50 to 80° C. for 4 to 6 hours.

[0026] The second aspect of the present application discloses a modified multi-walled carbon nanotube, which is prepared by the preparation method described above. The modified multi-walled carbon nanotube prepared by the method disclosed in the present application has an excellent coating effect, thereby significantly improving the performance of the multi-walled carbon nanotube in terms of electrical conductivity.

[0027] The third aspect of the present application discloses the use of the modified multi-walled carbon nanotubes described above in the preparation of polymer materials. The polymer materials described in the present application mainly refer to thermoplastic polymer materials, such as polypropylene materials, especially conductive polypropylene composite materials.

[0028] The fourth aspect of the present application discloses a conductive polypropylene composite material, the raw material components of which include the modified multi-walled carbon nanotubes described above.

[0029] It is understandable that, in addition to the modified multi-walled carbon nanotubes described above, the conductive polypropylene composite material may be added with functional additives commonly used in the art, such as antioxidants, lubricants, dispersants, etc., as needed, and the specific additives may be selected according to needs without special restrictions.

[0030] In some specific embodiments of the present application, the conductive polypropylene composite material is prepared from 83 to 89.5 parts of polypropylene, 10 to 16 parts of modified multi-walled carbon nanotubes, 0.2 to 0.4 parts of antioxidants and 0.3 to 0.6 parts of processing aids in parts by mass.

[0031] In the present application, the polypropylene is a homopolymer polypropylene or copolymer polypropylene commonly used in the art without any special limitation. In some specific embodiments of the present application, the melt index of the polypropylene under the test conditions of 230°C and 2.16kg is 3 to 100g / 10min.

[0032] In the present application, the antioxidant is a kind of auxiliary agent that can improve the antioxidant capacity of polypropylene materials, and specific types include hindered phenol antioxidants, phosphite antioxidants, thioester antioxidants, etc., and one of them can be selected, or two or more can be compounded. No further details will be given here.

[0033] In the present application, the processing aid is a type of additive that can reduce the flow resistance of the melt, or reduce the melt viscosity, or increase the fluidity of the melt to improve the processing performance. Specifically, it can be at least one of a dispersant and a lubricant. Specific examples that can be mentioned include one of dispersant E525, calcium stearate, and zinc stearate, but are not limited thereto.

[0034] The fifth aspect of the present application discloses a method for preparing the conductive polypropylene composite material as described above, comprising the following steps:

[0035] Polypropylene, modified multi-walled carbon nanotubes, antioxidants and processing aids are weighed according to the mass ratio, mixed evenly, and then added into a twin-screw extruder through a main feeding port for extrusion processing to obtain a conductive polypropylene composite material.

[0036] The mixing method is not particularly limited and is a conventional mechanical mixing method in the art, as long as the material components are fully mixed and uniform. Specific mixing conditions, such as rotation speed, time, etc., can be set as needed.

[0037] Further, in the present application, the processing conditions of the twin-screw extruder are not particularly limited, and those skilled in the art can select appropriate processing conditions through experience or experiments according to the specific raw material composition. In some specific embodiments of the present application, the temperature of each zone of the twin-screw extruder is 180-230°C; and / or the screw speed is 300-500r / min.

[0038] The following are specific embodiments of the present application. It should be noted that the following specific embodiments are only for illustrative purposes and do not limit the scope of the present application in any way.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0040] In addition, unless otherwise specified, methods without specific conditions or steps are conventional methods, and the reagents and materials used are all commercially available.

[0041] The specific raw material information used in the following examples and comparative examples is as follows:

[0042] Copolymer polypropylene: PP BX3800, SK, South Korea;

[0043] Homopolymer polypropylene: PP S2040, Shanghai Secco;

[0044] Multi-walled carbon nanotubes: LG Chem, with a tube diameter of 8 to 60 nm and a tube length of 20 to 100 μm;

[0045] Sodium dodecylbenzenesulfonate and pyrrole monomer: analytical grade, Sigma-Aldrich;

[0046] Antioxidant 1010: Irganox 1010, BASF;

[0047] Antioxidant 168: Irganox 168, BASF;

[0048] Antioxidant DSTDP: Naugard DSTDP, Artifact & Chemtura;

[0049] Dispersant E525, Evonik Degussa;

[0050] Calcium stearate, Henan Jiqian Biotechnology Co., Ltd.;

[0051] Zinc stearate, Xiong Innovation Materials Co., Ltd.

[0052] Example 1

[0053] 1. Preparation of modified multi-walled carbon nanotubes

[0054] (1) adding sodium dodecyl sulfate to water and dissolving it, stirring it at room temperature for 1.5 h, to obtain 150 mL of a sodium dodecyl sulfate solution having a concentration of 4 mmol / L;

[0055] (2) adding 1 g of multi-walled carbon nanotubes to the solution of step (1) and stirring at room temperature for 5 hours;

[0056] (3) adding 0.6 mL of pyrrole monomer to the mixed solution of step (2) and stirring for 2 hours; then adding 1.5 g of initiator ammonium persulfate to the above solution and stirring for 5 hours;

[0057] (4) The reaction product in step (3) is filtered, washed with deionized water for 4 times, and dried at 60° C. for 5 hours to obtain polypyrrole-coated multi-walled carbon nanotubes.

[0058] 2. Preparation of conductive polypropylene composite materials

[0059] According to the mass parts, 84.3 parts of polypropylene PP BX3800, 15 parts of modified multi-walled carbon nanotubes, 0.1 parts of antioxidant 1010, 0.2 parts of antioxidant 168 and 0.5 parts of processing aid E525 were weighed and mixed evenly, and then added into a twin-screw extruder through a main feeding port, extruded, stretched and granulated to obtain a conductive polypropylene composite material;

[0060] Among them, the process temperatures of the twin-screw extruder from the material port to the die port are: 190°C in zone 1, 190°C in zone 2, 200°C in zone 3, 200°C in zone 4, 200°C in zone 5, 210°C in zone 6, 210°C in zone 7, 210°C in zone 8, and 210°C in zone 9, and the screw speed is 400r / min.

[0061] Example 2

[0062] 1. Preparation of modified multi-walled carbon nanotubes

[0063] (1) Sodium dodecyl sulfate was added into water and dissolved and stirred at room temperature for 2 h to prepare 180 mL of a 5 mmol / L sodium dodecyl sulfate solution;

[0064] (2) adding 1 g of multi-walled carbon nanotubes to the solution of step (1) and stirring at room temperature for 6 hours;

[0065] (3) adding 0.5 mL of pyrrole monomer to the mixed solution of step (2) and stirring for 2 hours; then adding 1.8 g of initiator ammonium persulfate to the above solution and stirring for 4 hours;

[0066] (4) The reaction product of step (3) was filtered, washed with deionized water for 5 times, and dried at 70° C. for 5 hours to obtain polypyrrole-coated multi-walled carbon nanotubes.

[0067] 2. Preparation of conductive polypropylene composite materials

[0068] According to mass parts, 85.2 parts of polypropylene PP S2040, 14 parts of modified multi-walled carbon nanotubes, 0.1 parts of antioxidant 1010, 0.1 parts of antioxidant 168, 0.1 parts of antioxidant DSTDP and 0.5 parts of processing aid calcium stearate were weighed and mixed evenly, and then added into a twin-screw extruder through a main feeding port, extruded, stretched and granulated to obtain a conductive polypropylene composite material.

[0069] Among them, the process temperatures of the twin-screw extruder from the material port to the die port are: 190°C in zone 1, 200°C in zone 2, 200°C in zone 3, 210°C in zone 4, 210°C in zone 5, 220°C in zone 6, 220°C in zone 7, 210°C in zone 8, and 210°C in zone 9, and the screw speed is 450r / min.

[0070] Example 3

[0071] 1. Preparation of modified multi-walled carbon nanotubes

[0072] (1) Sodium dodecyl sulfate was added into water and dissolved and stirred at room temperature for 2 h to prepare 150 mL of sodium dodecyl sulfate solution with a concentration of 5 mmol / L;

[0073] (2) adding 1 g of multi-walled carbon nanotubes to the solution of step (1) and stirring at room temperature for 6 hours;

[0074] (3) adding 0.5 mL of pyrrole monomer to the mixed solution of step (2) and stirring for 3 hours; then adding 1.5 g of initiator ammonium persulfate to the above solution and stirring for 6 hours;

[0075] (4) The reaction product of step (3) is filtered, washed with deionized water for three times, and dried at 50° C. for 4 hours to obtain polypyrrole-coated multi-walled carbon nanotubes.

[0076] 2. Preparation of conductive polypropylene composite materials

[0077] 86.2 parts of polypropylene PP BX3800, 13 parts of modified multi-walled carbon nanotubes, 0.2 parts of antioxidant 1010, 0.2 parts of antioxidant 168 and 0.4 parts of processing aid zinc stearate were weighed and mixed evenly, and then added into a twin-screw extruder through a main feeding port, extruded, stretched and granulated to obtain a conductive polypropylene composite material.

[0078] Among them, the process temperatures of the twin-screw extruder from the material port to the die port are: 210°C in zone 1, 210°C in zone 2, 220°C in zone 3, 220°C in zone 4, 230°C in zone 5, 230°C in zone 6, 230°C in zone 7, 220°C in zone 8, and 220°C in zone 9, and the screw speed is 400r / min.

[0079] Example 4

[0080] 1. Preparation of modified multi-walled carbon nanotubes

[0081] (1) adding sodium dodecyl sulfate to water and dissolving it, stirring it at room temperature for 1 h, to prepare 100 mL of a sodium dodecyl sulfate solution with a concentration of 3 mmol / L;

[0082] (2) adding 1 g of multi-walled carbon nanotubes to the solution of step (1) and stirring at room temperature for 5 hours;

[0083] (3) adding 0.5 mL of pyrrole monomer to the mixed solution of step (2) and stirring for 1 hour; then adding 1.5 g of initiator ammonium persulfate to the above solution and stirring for 4 hours;

[0084] (4) The reaction product of step (3) is filtered, washed with deionized water for three times, and dried at 50° C. for 4 hours to obtain polypyrrole-coated multi-walled carbon nanotubes.

[0085] 2. Preparation of conductive polypropylene composite materials

[0086] 89.5 parts of polypropylene PP BX3800, 10 parts of modified multi-walled carbon nanotubes, 0.2 parts of antioxidant 168 and 0.3 parts of processing aid E525 were weighed and mixed evenly, and then added into a twin-screw extruder through a main feeding port, extruded, stretched and granulated to obtain a conductive polypropylene composite material.

[0087] Among them, the process temperatures of the twin-screw extruder from the material port to the die port are: 180°C in zone 1, 180°C in zone 2, 180°C in zone 3, 190°C in zone 4, 190°C in zone 5, 200°C in zone 6, 210°C in zone 7, 210°C in zone 8, and 200°C in zone 9, and the screw speed is 300r / min.

[0088] Example 5

[0089] 1. Preparation of modified multi-walled carbon nanotubes

[0090] (1) adding sodium dodecyl sulfate to water and dissolving it, stirring it at room temperature for 2 h, to prepare 200 mL of a sodium dodecyl sulfate solution with a concentration of 5 mmol / L;

[0091] (2) adding 1 g of multi-walled carbon nanotubes to the solution of step (1) and stirring at room temperature for 6 hours;

[0092] (3) adding 0.7 ml of pyrrole monomer to the mixed solution of step (2) and stirring for 3 hours; then adding 2 g of initiator ammonium persulfate to the above solution and stirring for 6 hours;

[0093] (4) The reaction product of step (3) is filtered, washed with deionized water for 5 times, and dried at 80° C. for 6 hours to obtain polypyrrole-coated multi-walled carbon nanotubes.

[0094] 2. Preparation of conductive polypropylene composite materials

[0095] According to mass parts, 83 parts of polypropylene PP BX3800, 16 parts of modified multi-walled carbon nanotubes, 0.2 parts of antioxidant 1010, 0.1 parts of antioxidant 168, 0.1 parts of antioxidant DSTDP and 0.6 parts of processing aid calcium stearate were weighed and mixed evenly, and then added into a twin-screw extruder through a main feeding port, extruded, stretched and granulated to obtain a conductive polypropylene composite material.

[0096] Among them, the process temperatures of the twin-screw extruder from the material port to the die port are: 210°C in zone 1, 210°C in zone 2, 210°C in zone 3, 230°C in zone 4, 230°C in zone 5, 230°C in zone 6, 230°C in zone 7, 230°C in zone 8, and 230°C in zone 9, and the screw speed is 500r / min.

[0097] Comparative Example 1

[0098] This comparative example discloses another method for preparing a conductive polypropylene composite material, which adopts the same implementation as in Example 1, except that the "modified multi-walled carbon nanotubes" in Example 1 are replaced with an equal mass portion of unmodified "multi-walled carbon nanotubes". The other process steps and condition parameters are the same as in Example 1.

[0099] The specific steps are as follows:

[0100] According to the mass parts, 84.3 parts of polypropylene PP BX3800, 15 parts of multi-walled carbon nanotubes, 0.1 parts of antioxidant 1010, 0.2 parts of antioxidant 168, and 0.5 parts of processing aid E525 were weighed and mixed evenly, and then added into a twin-screw extruder through a main feeding port, extruded, stretched, and granulated to obtain a conductive polypropylene composite material;

[0101] Among them, the process temperatures of the twin-screw extruder from the material port to the die port are: 190°C in zone 1, 190°C in zone 2, 200°C in zone 3, 200°C in zone 4, 200°C in zone 5, 210°C in zone 6, 210°C in zone 7, 210°C in zone 8, and 210°C in zone 9, and the screw speed is 400r / min.

[0102] Comparative Example 2

[0103] This comparative example discloses another method for preparing a conductive polypropylene composite material, which adopts the same implementation as in Example 1, except that the "modified multi-walled carbon nanotubes" in Example 1 are replaced with an equal mass portion of "conductive carbon black". The other process steps and condition parameters are the same as in Example 1.

[0104] The specific steps are as follows:

[0105] According to mass parts, 84.3 parts of polypropylene PP BX3800, 15 parts of conductive carbon black, 0.1 parts of antioxidant 1010, 0.2 parts of antioxidant 168, and 0.5 parts of processing aid E525 were weighed and mixed evenly, and then added into a twin-screw extruder through a main feeding port, extruded, stretched, and granulated to obtain a conductive polypropylene composite material.

[0106] Among them, the process temperatures of the twin-screw extruder from the material port to the die port are: 190°C in zone 1, 190°C in zone 2, 200°C in zone 3, 200°C in zone 4, 200°C in zone 5, 210°C in zone 6, 210°C in zone 7, 210°C in zone 8, and 210°C in zone 9, and the screw speed is 400r / min.

[0107] Comparative Example 3

[0108] This comparative example discloses another method for preparing a conductive polypropylene composite material, which adopts the same implementation as in Example 1, except that the mass proportion of unmodified multi-walled carbon nanotubes is increased. Other process steps and condition parameters are the same as in Example 1.

[0109] The specific steps are as follows:

[0110] According to mass parts, 64.3 parts of polypropylene PP BX3800, 35 parts of multi-walled carbon nanotubes, 0.1 parts of antioxidant 1010, 0.2 parts of antioxidant 168, and 0.5 parts of processing aid E525 were weighed and mixed evenly, and then added into a twin-screw extruder through a main feeding port, extruded, stretched, and granulated to obtain a conductive polypropylene composite material.

[0111] Among them, the process temperatures of the twin-screw extruder from the material port to the die port are: 190°C in zone 1, 190°C in zone 2, 200°C in zone 3, 200°C in zone 4, 200°C in zone 5, 210°C in zone 6, 210°C in zone 7, 210°C in zone 8, and 210°C in zone 9, the side feed port is opened in zone 8, and the screw speed is 400r / min.

[0112] Performance Testing

[0113] The conductive polypropylene composite materials prepared in Examples 1-5 and Comparative Examples 1-3 were respectively prepared into discs with a diameter of 8.5 cm and a thickness of 4 mm, and the surface resistance was tested in accordance with the standard GB1410. The results are shown in Table 1.

[0114] Table 1 Surface resistance test results of conductive polypropylene composite materials

[0115] Test items Surface resistance / Ω Example 1 <![CDATA[7.2×10 2 ]]> Example 2 <![CDATA[6.4×10 2 ]]> Example 3 <![CDATA[2.8×10 3 ]]> Example 4 <![CDATA[4.4×10 3 ]]> Example 5 <![CDATA[6.5×10 2 ]]> Comparative Example 1 <![CDATA[4.3×10 11 ]]> Comparative Example 2 <![CDATA[4.8×10 12 ]]> Comparative Example 3 <![CDATA[3.3×10 5 ]]>

[0116] It can be seen from the test results in Table 2 that the conductive polypropylene composite material prepared in the embodiment of the present application has a lower surface resistance, indicating that it has excellent conductive properties. This is due to the introduction of polypyrrole-coated multi-walled carbon nanotubes, which can significantly improve the conductive properties while significantly reducing the amount of added polypyrrole and reduce the overall cost of the material.

[0117] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, within the scope of the subject matter of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing modified multi-walled carbon nanotubes, characterized in that: The following steps are involved: S1. Take sodium dodecyl sulfate and add it into water to fully dissolve it to prepare a sodium dodecyl sulfate solution with a concentration of 3 to 5 mmol / L; S2, adding multi-walled carbon nanotubes to the above solution and stirring for 5 to 6 hours; S3, adding pyrrole monomer to the mixed solution of step S2 and stirring for 1 to 3 hours; then adding initiator ammonium persulfate to the above solution, stirring and reacting at 20 to 30° C. for 4 to 6 hours to obtain polypyrrole-coated multi-walled carbon nanotubes.

2. The preparation method according to claim 1, characterized in that Every 1g of multi-walled carbon nanotubes corresponds to 100-200mL of sodium dodecyl sulfate solution, 0.5-0.7mL of pyrrole monomer, and 1.5-2g of initiator ammonium persulfate.

3. The preparation method according to claim 1, characterized in that: The multi-walled carbon nanotubes have a tube diameter of 8 to 60 nm and a tube length of 20 to 100 μm.

4. A modified multi-walled carbon nanotube, characterized in that: The method is prepared by the method according to any one of claims 1 to 3.

5. Use of the modified multi-walled carbon nanotubes according to claim 4 in the preparation of polymer materials; Preferably, the polymer material is a conductive polypropylene composite material.

6. A conductive polypropylene composite material, characterized in that: The raw material components include the modified multi-walled carbon nanotubes as claimed in claim 4; Preferably, the conductive polypropylene composite material is prepared from 83 to 89.5 parts of polypropylene, 10 to 16 parts of modified multi-walled carbon nanotubes, 0.2 to 0.4 parts of antioxidants and 0.3 to 0.6 parts of processing aids in parts by mass.

7. The conductive polypropylene composite material according to claim 6, characterized in that: The polypropylene is homopolymer polypropylene or copolymer polypropylene, and the melting index of the polypropylene under the test conditions of 230° C. and 2.16 kg is 3 to 100 g / 10 min.

8. The conductive polypropylene composite material according to claim 6, characterized in that: The antioxidant is at least one of a hindered phenol antioxidant, a phosphite antioxidant, and a thioester antioxidant.

9. The conductive polypropylene composite material according to claim 6, characterized in that: The processing aid is one of dispersant E525, calcium stearate and zinc stearate.

10. A method for preparing the conductive polypropylene composite material according to any one of claims 6 to 9, characterized in that: The following steps are involved: Weigh polypropylene, modified multi-walled carbon nanotubes, antioxidants and processing aids according to the mass ratio, mix them evenly, and then add them into a twin-screw extruder through a main feeding port for extrusion processing to obtain a conductive polypropylene composite material; Preferably, the temperature of each zone of the twin-screw extruder is 180-230° C.; and / or the screw speed is 300-500 r / min.