Weakly conductive polypropylene composite material and method for producing the same

Abstract

The application discloses a weakly conductive polypropylene composite material and a preparation method thereof, which is prepared from 0.1-1 parts of carbon nanotubes, 5-25 parts of inorganic fillers, 0.3-0.9 parts of antioxidants, 0.1-0.5 parts of processing aids, 49-85 parts of polypropylene, 5-10 parts of polyethylene, 3-10 parts of toughening agents and 2-6 parts of compatilizers according to weight parts; the carbon nanotubes are treated at a high temperature above 1200 DEG C. The weakly conductive effect is achieved by adding the carbon nanotubes, the adding amount is very low, the surface resistivity of the polypropylene can be reduced, and the mechanical property of the material is less affected.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a weakly conductive polypropylene composite material and its preparation method. Background Technology

[0002] Conductive plastics are now widely used in automobiles, home appliances, electronics, packaging, building materials, and other fields. Polypropylene, due to its ease of processing, impact strength, and flexibility, also has a wide range of applications in these fields; however, its insulation properties limit its use. Research on composite conductive materials is extensive, but many problems remain unresolved. For example, while adding a conductive medium to improve conductivity, mechanical properties decrease. Therefore, the development of composite conductive materials mainly focuses on reducing resistivity and improving the overall performance of the material. Summary of the Invention

[0003] The purpose of this invention is to provide a weakly conductive polypropylene composite material and its preparation method, so as to solve the problems mentioned in the background art, which can make the conductivity of the composite material sufficiently low while ensuring the mechanical properties of the composite material.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] This invention discloses a weakly conductive polypropylene composite material, which is prepared by weight of 0.1-1 parts carbon nanotubes, 5-25 parts inorganic fillers, 0.3-0.9 parts antioxidants, 0.1-0.5 parts processing aids, 49-85 parts polypropylene, 5-10 parts polyethylene, 3-10 parts toughening agents, and 2-6 parts compatibilizers; wherein the carbon nanotubes are subjected to high-temperature treatment at 1200℃ or above.

[0006] Furthermore, the carbon nanotubes have a diameter of 10-30 nm and a length of 5-30 μm.

[0007] Furthermore: the compatibilizer is glycidyl methacrylate-grafted polypropylene with a grafting rate of 1.2-3.0%; the inorganic filler is calcium carbonate or barium sulfate; the toughening agent is ethylene-1-octene copolymer, ethylene-propylene polymer, or ethylene-1-butene polymer; and the antioxidant is a mixture of hindered phenolic antioxidant and phosphite antioxidant in a 1:2 ratio.

[0008] Furthermore: the polypropylene is a copolymer polypropylene with a melt index of 10-40 g / 10 min at 230℃ / 2.16 kg and an ethylene content of 5-10%.

[0009] Furthermore: the polyethylene is high-density polyethylene, and its melt index is 3-25g / 10min at 190℃ / 2.16kg.

[0010] Furthermore: the processing aid is silicone powder or erucamide.

[0011] Another aspect of the present invention discloses a method for preparing a polypropylene composite material as described above, comprising the following steps:

[0012] S1: Place carbon nanotubes in a sintering furnace under pure nitrogen protection and react for 4-5 hours at a temperature above 1200℃.

[0013] S2: Weigh 0.1-1 parts by weight of carbon nanotubes, 5-25 parts by weight of inorganic filler, 0.3-0.9 parts by weight of antioxidant, and 0.1-0.5 parts by weight of processing aid, and mix them evenly in a high-speed mixer to obtain the first mixture;

[0014] S3: Weigh 49-85 parts of polypropylene, 5-10 parts of polyethylene, 3-10 parts of toughening agent and 2-6 parts of compatibilizer by weight, and add them to the first mixture and mix evenly to obtain the second mixture;

[0015] S4: The second mixture is added to a twin-screw extruder for granulation to obtain a weakly conductive polypropylene composite material.

[0016] Furthermore, the mixing step in step S2 specifically involves mixing at room temperature for 2-4 minutes, followed by a second mixing at 90-100℃ for 3-5 minutes.

[0017] Furthermore, the mixing time in step S3 is 4-6 minutes, and the mixing temperature is room temperature.

[0018] Furthermore: In step S4, the temperature of each zone of the twin-screw extruder is 180-220℃.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. This invention achieves weak conductivity by adding carbon nanotubes. The amount added is extremely low, which can reduce the surface resistivity of polypropylene and has little impact on the mechanical properties of the material.

[0021] 2. After high-temperature surface treatment, the resistivity of the carbon nanotubes used in this invention is reduced by 0.1 Ω·cm compared with that before treatment, which is more conducive to the production of weakly conductive polypropylene materials. In addition, this surface treatment method does not require acid or alkali treatment, and the operation method is simple, safe and convenient.

[0022] 3. In the preparation method of the composite material of the present invention, the powdered components are first mixed at room temperature and then mixed at high temperature. Since the amount of carbon nanotubes added is low, mixing at room temperature first can pre-disperse the carbon nanotubes; then mixing at 95°C can melt the processing aids into the mixture, which can play a better lubricating role.

[0023] 4. This invention uses glycidyl methacrylate grafted polypropylene as a compatibilizer, which can improve the interfacial bonding force between the PP matrix and inorganic fillers and carbon nanotubes, thereby improving the conductivity of the composite material. Detailed Implementation

[0024] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0026] The specific information on the main raw materials and equipment used in the following embodiments and comparative examples is as follows:

[0027] Twin-screw extruder: length-to-diameter ratio 44:1, manufactured by Kunshan Kexin Rubber & Plastic Machinery Co., Ltd.

[0028] Polypropylene: Manufacturer is Basel BX3800.

[0029] Polyethylene: The manufacturer is Fushun Petrochemical 2911.

[0030] Toughening agent: Manufacturer is Dow POE8200.

[0031] Carbon nanotubes: 22 nm in diameter and 7 μm in length; calcium carbonate: 3000 mesh.

[0032] Antioxidant 1010, Antioxidant 168, Erucamide, and Silicone Powder are commercially available.

[0033] Compatibilizer: The preparation method of glycidyl methacrylate-grafted polypropylene (PP-g-GMA) is as follows:

[0034] (1) Grind polypropylene into powder using a grinder, and then sieve it through a 40-mesh filter to obtain polypropylene powder;

[0035] (2) Heat the mixer to 80°C, add 100 parts of polypropylene powder, stir at 60 rpm for 10 min, then add 10 parts of glycidyl methacrylate and 10 parts of benzoyl peroxide, adjust the mixer temperature to 120°C, adjust the speed to 100 rpm, stir for 60 min, and obtain the mixture.

[0036] (3) The mixture was washed with water until neutral, then washed once with isopropanol, and dried at 100°C for 6 hours to obtain compatibilizer PP-g-GMA.

[0037] In step (1), the polypropylene used is homopolymer polypropylene, which has a melt index of 3 g / 10 min at 230℃ and 2.16 kg. The "parts" in the compatibilizer preparation method refer to parts by weight.

[0038] Except for the compatibilizer, all materials are commercially available, commonly used products.

[0039] It is understood that the above-mentioned raw materials and reagents are merely examples of some specific embodiments of the present invention, making the technical solution of the present invention clearer, and do not mean that the present invention can only use the above-mentioned reagents. The specific scope shall be determined by the claims. In addition, unless otherwise specified, "parts" in the examples and comparative examples refer to parts by weight.

[0040] Example 1

[0041] (1) Carbon nanotubes were placed in a sintering furnace and reacted for 4 hours at a temperature of 1200℃.

[0042] (2) Weigh 0.1 parts of carbon nanotubes, 25 parts of calcium carbonate, 0.3 parts of antioxidant 1010, 0.6 parts of antioxidant 168, and 0.5 parts of silicone powder and put them into a high-speed mixer. Mix at room temperature for 2 minutes, and then mix at 95°C for 3 minutes to obtain the first mixture.

[0043] (3) Add 49 parts of polypropylene, 10 parts of polyethylene, 10 parts of toughening agent, and 6 parts of compatibilizer PP-g-GMA to the first mixture, and mix at room temperature for 4 minutes to obtain the second mixture.

[0044] (4) The second mixture is added to a twin-screw extruder with temperatures of 180℃, 190℃, 200℃, 205℃, 210℃, 210℃, 215℃, 220℃ and 210℃ in each zone for extrusion granulation to obtain a weakly conductive polypropylene composite material, denoted as X1.

[0045] Example 2

[0046] (1) Carbon nanotubes were placed in a sintering furnace and reacted for 4 hours at a temperature of 1200℃.

[0047] (2) Weigh 1 part of carbon nanotubes, 5 parts of calcium carbonate, 0.1 part of antioxidant 1010, 0.2 part of antioxidant 168, and 0.3 parts of silicone powder and put them into a high-speed mixer. Mix at room temperature for 2 minutes, and then mix at 95°C for 3 minutes to obtain the first mixture.

[0048] (3) Add 85 parts of polypropylene, 5 parts of polyethylene, 3 parts of toughening agent and 2 parts of compatibilizer PP-g-GMA to the first mixture, mix at room temperature for 4 min to obtain the second mixture;

[0049] (4) The second mixture was added to a twin-screw extruder with temperatures of 180℃, 190℃, 200℃, 205℃, 210℃, 210℃, 215℃, 220℃ and 210℃ in each zone for extrusion granulation to obtain a weakly conductive polypropylene composite material, denoted as X2.

[0050] Example 3

[0051] (1) Carbon nanotubes were placed in a sintering furnace and reacted for 4 hours at a temperature of 1200℃.

[0052] (2) Weigh 0.5 parts of carbon nanotubes, 10 parts of calcium carbonate, 0.2 parts of antioxidant 1010, 0.4 parts of antioxidant 168, and 0.1 parts of erucamide and put them into a high-speed mixer. Mix at room temperature for 2 minutes, and then mix at 95°C for 3 minutes to obtain the first mixture.

[0053] (3) Add 72 parts of polypropylene, 8 parts of polyethylene, 6 parts of toughening agent and 4 parts of compatibilizer PP-g-GMA to the first mixture, mix at room temperature for 4 min to obtain the second mixture;

[0054] (4) The second mixture was added to a twin-screw extruder with temperatures of 180℃, 190℃, 200℃, 205℃, 210℃, 210℃, 215℃, 220℃ and 210℃ in each zone for extrusion granulation to obtain a weakly conductive polypropylene composite material, denoted as X3.

[0055] Example 4

[0056] (1) Carbon nanotubes were placed in a sintering furnace and reacted for 4 hours at a temperature of 1200℃.

[0057] (2) Weigh 0.6 parts of carbon nanotubes, 15 parts of calcium carbonate, 0.2 parts of antioxidant 1010, 0.4 parts of antioxidant 168, and 0.25 parts of erucamide and put them into a high-speed mixer. Mix at room temperature for 2 minutes, and then mix at 95°C for 3 minutes to obtain the first mixture.

[0058] (3) Add 75 parts of polypropylene, 7 parts of polyethylene, 5 parts of toughening agent and 3 parts of compatibilizer PP-g-GMA to the first mixture, mix at room temperature for 4 min to obtain the second mixture;

[0059] (4) The second mixture is added to a twin-screw extruder with temperatures of 180℃, 190℃, 200℃, 205℃, 210℃, 210℃, 215℃, 220℃ and 210℃ in each zone for extrusion granulation to obtain a weakly conductive polypropylene composite material, denoted as X4.

[0060] Example 5

[0061] (1) Carbon nanotubes were placed in a sintering furnace and reacted for 4 hours at a temperature of 1200℃.

[0062] (2) Weigh 0.8 parts of carbon nanotubes, 20 parts of calcium carbonate, 0.2 parts of antioxidant 1010, 0.4 parts of antioxidant 168, and 0.4 parts of erucamide and put them into a high-speed mixer. Mix at room temperature for 2 minutes, and then mix at 95°C for 3 minutes to obtain the first mixture.

[0063] (3) Add 60 parts of polypropylene, 8 parts of polyethylene, 7 parts of toughening agent and 5 parts of compatibilizer PP-g-GMA to the first mixture and put them into a high-speed mixer. Mix at room temperature for 4 minutes to obtain the second mixture.

[0064] (4) The second mixture is added to a twin-screw extruder with temperatures of 180℃, 190℃, 200℃, 205℃, 210℃, 210℃, 215℃, 220℃ and 210℃ in each zone for extrusion granulation to obtain a weakly conductive polypropylene composite material, denoted as X5.

[0065] Comparative Example 1

[0066] (1) Weigh 20 parts of calcium carbonate, 0.2 parts of antioxidant 1010, 0.4 parts of antioxidant 168, and 0.4 parts of erucamide and put them into a high-speed mixer. Mix at room temperature for 2 minutes, and then mix at 95°C for 3 minutes to obtain the first mixture.

[0067] (2) Add 60 parts of polypropylene, 8 parts of polyethylene, 7 parts of toughening agent and 5 parts of compatibilizer PP-g-GMA to the first mixture and put them into a high-speed mixer. Mix at room temperature for 4 minutes to obtain the second mixture.

[0068] (3) The second mixture is added to a twin-screw extruder with temperatures of 180℃, 190℃, 200℃, 205℃, 210℃, 210℃, 215℃, 220℃ and 210℃ in each zone for extrusion granulation to obtain a weakly conductive polypropylene composite material, denoted as D5.

[0069] Comparative Example 2

[0070] (1) The conductive carbon black was placed in a sintering furnace and reacted for 4 hours at a temperature of 1200℃.

[0071] (2) Weigh 15 parts of conductive carbon black, 15 parts of calcium carbonate, 0.2 parts of antioxidant 1010, 0.4 parts of antioxidant 168, and 0.25 parts of erucamide and put them into a high-speed mixer. Mix at room temperature for 2 minutes, and then mix at 95°C for 3 minutes to obtain the first mixture.

[0072] (3) Add 75 parts of polypropylene, 7 parts of polyethylene, 5 parts of toughening agent and 3 parts of compatibilizer PP-g-GMA to the first mixture, mix at room temperature for 4 min to obtain the second mixture;

[0073] (4) The second mixture is added to a twin-screw extruder with temperatures of 180℃, 190℃, 200℃, 205℃, 210℃, 210℃, 215℃, 220℃ and 210℃ in each zone for extrusion granulation to obtain a weakly conductive polypropylene composite material, denoted as D2.

[0074] Comparative Example 3

[0075] (1) Place 0.8 parts of carbon nanotubes, 20 parts of calcium carbonate, 0.2 parts of antioxidant 1010, 0.4 parts of antioxidant 168, 0.4 parts of erucamide, 50 parts of polypropylene, 8 parts of polyethylene, 7 parts of toughening agent, and 5 parts of compatibilizer PP-g-GMA into a high-speed mixer and mix at room temperature for 4 minutes to obtain a mixture;

[0076] (2) The mixture from step (1) is added to a twin-screw extruder with temperatures of 180℃, 190℃, 200℃, 205℃, 210℃, 210℃, 215℃, 220℃ and 210℃ in each zone for extrusion granulation to obtain a weakly conductive polypropylene composite material, denoted as D3.

[0077] Comparative Example 4

[0078] (1) Carbon nanotubes were placed in a sintering furnace and reacted for 4 hours at a temperature of 1200℃.

[0079] (2) Weigh 0.8 parts of carbon nanotubes, 20 parts of calcium carbonate, 0.2 parts of antioxidant 1010, 0.4 parts of antioxidant 168, and 0.4 parts of erucamide and put them into a high-speed mixer. Mix at room temperature for 2 minutes, and then mix at 95°C for 3 minutes to obtain the first mixture.

[0080] (3) Add 60 parts of polypropylene, 8 parts of polyethylene, 7 parts of toughening agent and 5 parts of maleic anhydride-grafted polypropylene compatibilizer to the first mixture and put them into a high-speed mixer. Mix at room temperature for 4 minutes to obtain the second mixture.

[0081] (4) The second mixture is added to a twin-screw extruder with temperatures of 180℃, 190℃, 200℃, 205℃, 210℃, 210℃, 215℃, 220℃ and 210℃ in each zone for extrusion granulation to obtain a weakly conductive polypropylene composite material, denoted as D4.

[0082] Comparative Example 5

[0083] (1) Carbon nanotubes were placed in a sintering furnace and reacted for 4 hours at a temperature of 500℃.

[0084] (2) Weigh 0.8 parts of carbon nanotubes, 20 parts of calcium carbonate, 0.2 parts of antioxidant 1010, 0.4 parts of antioxidant 168, and 0.4 parts of erucamide and put them into a high-speed mixer. Mix at room temperature for 2 minutes, and then mix at 95°C for 3 minutes to obtain the first mixture.

[0085] (3) Add 60 parts of polypropylene, 8 parts of polyethylene, 7 parts of toughening agent and 5 parts of compatibilizer PP-g-GMA to the first mixture and put them into a high-speed mixer. Mix at room temperature for 4 minutes to obtain the second mixture.

[0086] (4) The second mixture is added to a twin-screw extruder with temperatures of 180℃, 190℃, 200℃, 205℃, 210℃, 210℃, 215℃, 220℃ and 210℃ in each zone for extrusion granulation to obtain a weakly conductive polypropylene composite material, denoted as D5.

[0087] The weakly conductive polypropylene composite materials X1-X5 obtained in Examples 1-5 and the weakly conductive polypropylene composite materials D1-D5 obtained in Comparative Examples 1-5 were injection molded to obtain test specimens. After stabilization at 23°C and 50% relative humidity for 24 hours, performance tests were conducted. The test items and test standards are as follows:

[0088] Melt flow index: Tested according to ISO 1133 standard at a temperature of 230℃ and a load of 2.16kg.

[0089] Surface resistivity: Samples were prepared and tested according to IEC 62631 standard. Sample diameter: Sample thickness: 3mm;

[0090] Flexural modulus: Samples were prepared and tested according to ISO 178 standard. Sample size: 80mm*10mm*4mm. Test conditions: 2mm / min.

[0091] The performance test results are shown in Table 1-2:

[0092] Table 1

[0093] Test Project Example 1 Example 2 Example 3 Example 4 Example 5 Melt index / g / 10min 11.2 18.5 15.3 15.9 13.9 Flexural modulus / MPa 1320 1589 1492 1526 1583 Surface resistivity / Ω 2.9×10(7) 1.2×10(2) 2.2×10(5) 3.2×10(4) 1.8×10(3)

[0094] Table 2

[0095] Test Project Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Melt index / g / 10min 14.1 3.9 13.3 13.3 13.5 Flexural modulus / MPa 1562 1629 1487 1362 1492 Surface resistivity / Ω 5.6×10(16) 2.6×10(7) 3.4×10(5) 6.8×10(5) 7.8×10(4)

[0096] As can be seen from Table 1-2, compared with Comparative Example 1, the PP modified composite material without carbon nanotubes in Example 5 has a surface resistivity of 5.6×10(16), which is an insulating material; Comparative Example 3 is a one-step mixing method, and compared with the step-by-step mixing in Example 5, the surface resistivity is two orders of magnitude higher, and the conductivity is greatly reduced; Compared with Comparative Example 2, the weakly conductive polypropylene composite material made by adding conductive carbon black in Example 4 has a surface resistivity of only 2.6×10(7) due to the high addition amount and poor dispersibility, and the melt index is much lower, which is not conducive to injection molding; Compared with Example 5, Comparative Example 4 uses maleic anhydride grafted polypropylene as a compatibilizer, and the compatibility of its system is worse. Although its surface resistivity also reaches the weakly conductive level, it is two orders of magnitude lower than that of Example 5; This shows that PP-g-GMA as a compatibilizer has a synergistic effect with the antioxidant, toughening agent, processing aid, inorganic filler, etc., which improves the weak conductivity of the material. Examples 5 and Comparative Example 5 demonstrate the necessity of high-temperature treatment of carbon nanotubes above 1200°C, which effectively improves the conductivity of polypropylene composite materials.

[0097] Although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0098] Therefore, the above description is only a preferred embodiment of this application and is not intended to limit the scope of this application; that is, all equivalent modifications made in accordance with the scope of the claims of this application shall be within the protection scope of the claims of this application.

Claims

1. A weakly conductive polypropylene composite material, characterized in that, It is prepared by weight of 0.1-1 parts carbon nanotubes, 5-25 parts inorganic fillers, 0.3-0.9 parts antioxidants, 0.1-0.5 parts processing aids, 49-85 parts polypropylene, 5-10 parts polyethylene, 3-10 parts toughening agents, and 2-6 parts compatibilizers; the carbon nanotubes are treated at a high temperature above 1200℃. The carbon nanotubes have a diameter of 10-30 nm and a length of 5-30 μm; The compatibilizer is glycidyl methacrylate-grafted polypropylene with a grafting rate of 1.2-3.0%; the inorganic filler is calcium carbonate or barium sulfate; the toughening agent is ethylene-1-octene copolymer, ethylene-propylene polymer, or ethylene-1-butene polymer; the antioxidant is a mixture of hindered phenolic antioxidant and phosphite antioxidant in a 1:2 ratio. The processing aid is silicone powder or erucamide; The preparation method of the weakly conductive polypropylene composite material includes the following steps: S1: Place carbon nanotubes in a sintering furnace under pure nitrogen protection and react for 4-5 hours at a temperature above 1200℃. S2: Weigh 0.1-1 parts by weight of carbon nanotubes, 5-25 parts by weight of inorganic filler, 0.3-0.9 parts by weight of antioxidant, and 0.1-0.5 parts by weight of processing aid, and mix them evenly in a high-speed mixer to obtain the first mixture; S3: Weigh 49-85 parts of polypropylene, 5-10 parts of polyethylene, 3-10 parts of toughening agent and 2-6 parts of compatibilizer by weight, and add them to the first mixture and mix evenly to obtain the second mixture; S4: The second mixture is added to a twin-screw extruder for granulation to obtain a weakly conductive polypropylene composite material.

2. The weakly conductive polypropylene composite material according to claim 1, characterized in that, The polypropylene is a copolymer polypropylene with a melt index of 10-40 g / 10 min at 230℃ / 2.16 kg and an ethylene content of 5-10%.

3. The weakly conductive polypropylene composite material according to claim 1, characterized in that, The polyethylene is high-density polyethylene, and its melt index is 3-25 g / 10 min at 190℃ / 2.16 kg.

4. The weakly conductive polypropylene composite material according to claim 1, characterized in that, The mixing step in step S2 is as follows: first mix at room temperature for 2-4 minutes, and then mix a second time at 90-100℃ for 3-5 minutes.

5. The weakly conductive polypropylene composite material according to claim 1, characterized in that, The mixing time in step S3 is 4-6 minutes, and the mixing temperature is room temperature.

6. The weakly conductive polypropylene composite material according to claim 1, characterized in that, In step S4, the temperature of each zone of the twin-screw extruder is 180-220℃.