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CN-121779828-B - Conductive polypropylene composite material and preparation method thereof

CN121779828BCN 121779828 BCN121779828 BCN 121779828BCN-121779828-B

Abstract

The invention relates to the technical field of resin, in particular to a conductive polypropylene composite material and a preparation method thereof. Aiming at the problems of poor processing fluidity, easy shearing damage of a conductive network and deterioration of mechanical properties caused by high-filling conductive filler in the prior art, the invention adopts a solid-phase pre-coating technology to firstly position carboxylated multi-wall carbon nanotubes and graphene nano sheets on the surface of polypropylene powder under the action of stearic acid, then carry out solid-phase mixing with difunctional group grafted modified graphite phase carbon nitride and maleic anhydride grafted polypropylene to pre-construct an interface layer, finally carry out staged melt mixing with polypropylene resin and polyolefin elastomer, and control the temperature time sequence to add an initiator and an antioxidant. The method realizes low volume resistivity, high melt flow rate and excellent mechanical toughness under the condition of low filler consumption, and effectively balances conductivity, processability and strength.

Inventors

  • LIANG YICHEN

Assignees

  • 厦门众臣元科技有限公司
  • 厦门臣匠供应链科技有限公司

Dates

Publication Date
20260512
Application Date
20260305

Claims (8)

  1. 1. The preparation method of the conductive polypropylene composite material is characterized by comprising the following steps of: (1) Preparing polypropylene powder with the particle size of 75-150 mu m; (2) Carrying out solid-phase pre-coating mixing on polypropylene powder, stearic acid, carboxylated multiwall carbon nanotubes and graphene nano sheets under a heating condition to obtain solid-phase pre-coating composite powder; (3) Solid phase pre-coating composite powder is subjected to solid phase mixing with difunctional grafting modified graphite phase carbon nitride and maleic anhydride grafting polypropylene to obtain an interface layer pre-constructed mixture; (4) Melting and mixing the mixture pre-constructed in the interface layer, polypropylene resin and polyolefin elastomer at a first temperature, then raising the mixing temperature to a second temperature higher than the first temperature, adding an initiator at the second temperature for continuous mixing, adding an antioxidant, discharging and granulating to obtain the conductive polypropylene composite material; The difunctional grafting modified graphite phase carbon nitride is prepared by mixing graphite phase carbon nitride with N, N-dimethylformamide, decompressing and dehydrating at 50 ℃ for 20-40min, introducing dry nitrogen for protection, stirring at 700-900rpm, ultrasonically dispersing for 20-40min to form suspension, adding triethylamine, dropping methacryloyl chloride into the suspension at 0 ℃ for 20-40min, maintaining the stirring at 0 ℃ for 45-75min, rising to 30 ℃ for reacting for 2-4h, dropping stearoyl chloride, reacting at 40 ℃ for 1-3h, filtering and washing after the reaction is finished, and vacuum drying to obtain difunctional grafting modified graphite phase carbon nitride; The mass ratio of the graphite phase carbon nitride to the methacryloyl chloride to the stearoyl chloride is 20 (18-22) to 25-35; the graphite phase carbon nitride is obtained by heating melamine to 540-560 ℃ at the temperature of 4-6 ℃ per min, preserving heat for 3-5 hours, naturally cooling to room temperature, grinding and sieving with a 200-mesh sieve; In the step (2), solid-phase pre-coating mixing is carried out in a jacketed high-speed mixer, the temperature of the jacket is 70-80 ℃, premixing is carried out for 4-6min at 500-700rpm, stirring is carried out for 12-18min at 1000-1400rpm, and the materials are cooled to below 40 ℃ and discharged; In the step (2), the mass ratio of the polypropylene powder to the stearic acid to the carboxylated multi-wall carbon nano tube to the graphene nano sheet is (567-593): 8-12): 16-24): 4-6; In the step (3), the mass ratio of the solid-phase pre-coated composite powder to the difunctional group grafted modified graphite phase carbon nitride to the maleic anhydride grafted polypropylene is (609-621) to (4-6) to (15-25); In the step (4), the mass ratio of the mixture pre-constructed by the interface layer, the polypropylene resin, the polyolefin elastomer, the initiator and the antioxidant is 640 (260-300) (70-110) (2-4) (3); in the step (4), the first temperature is 150 ℃ and the mixing is carried out for 2-4min, the second temperature is 170 ℃ and the mixing is continued for 1-3min after the initiator is added.
  2. 2. The method for preparing a conductive polypropylene composite material according to claim 1, wherein in the step (1), the polypropylene powder is obtained by pre-cooling polypropylene particles in liquid nitrogen after drying, pulverizing at a low temperature, and sieving, and the particle size of the polypropylene powder is 75-150 μm.
  3. 3. The method for producing a conductive polypropylene composite material according to claim 1, wherein in the step (1), the polypropylene powder is homo-polypropylene and the melt mass flow rate at 230 ℃ per 2.16kg is 12g/10min.
  4. 4. The method for preparing a conductive polypropylene composite material according to claim 1, wherein in the step (3), the solid phase mixing is performed in a jacketed high-speed mixer, the temperature of the jacket is 125-145 ℃, the stirring speed is 700-900rpm, the mixing time is 6-10min, and the materials are cooled to below 40 ℃ and discharged.
  5. 5. The method of producing a conductive polypropylene composite according to claim 1, wherein in the step (4), the initiator is dicumyl peroxide polymer coated particles, and the model is Perkadox BC-EP40.
  6. 6. The method for producing a conductive polypropylene composite material according to claim 1, wherein in the step (4), the polypropylene resin is a polypropylene random copolymer, and the melt mass flow rate at 230 ℃ per 2.16kg is 11g/10min.
  7. 7. The method of producing a conductive polypropylene composite according to claim 1, wherein in the step (4), the polyolefin elastomer has a melt mass flow rate of 0.5g/10min at 190 ℃ per 2.16 kg.
  8. 8. A conductive polypropylene composite material, characterized in that it is obtained by the method for producing a conductive polypropylene composite material according to any one of claims 1 to 7.

Description

Conductive polypropylene composite material and preparation method thereof Technical Field The invention relates to the technical field of resin, in particular to a conductive polypropylene composite material and a preparation method thereof. Background The conductive polymer composite material has wide requirements in the fields of electronics, automobiles, aerospace and the like for antistatic, electromagnetic shielding and the like. Polypropylene is a versatile plastic whose insulating nature requires functionalization by addition of conductive fillers. The traditional technical route relies mainly on highly filled carbon black or metal powders. Although the cost of the carbon black is lower, the addition amount required for reaching the conductive percolation threshold is usually up to 15-20wt%, the melt flow property of the material is seriously deteriorated, the injection molding difficulty is caused, the internal stress of the product is increased, the toughness of a matrix is obviously sacrificed, and the embrittlement of the composite material is obvious. Although the metal filler has high conductive efficiency, the metal filler has high density, is easy to oxidize and has high cost, and orientation or migration is easy to occur in the high-shear processing process, so that the conductive performance is unstable. In order to reduce the percolation threshold, novel nano carbon materials such as carbon nanotubes, graphene and the like are introduced. They can construct a conductive network with a low addition amount theoretically by virtue of their high aspect ratio or large specific surface area. However, dispersion of nanocarbon materials in polypropylene melts is a great challenge. The strong van der Waals force makes the agglomeration very easy, the shearing force of conventional melt blending is difficult to realize uniform dispersion of nano scale, and local enriched agglomerates are often formed instead of an ideal three-dimensional interconnected network. Not only does this limit the improvement of the conductivity, but the agglomerates also become stress concentration points, further deteriorating the mechanical properties. Aiming at the dispersibility problem, the prior art mostly adopts a method for carrying out surface modification on the filler or adding a compatilizer. For example, carboxyl groups are introduced on the surface of carbon nanotubes by acid oxidation, or maleic anhydride grafted polypropylene is used as a compatibilizer, with the aim of improving the interfacial affinity of the filler with the polypropylene matrix. However, these methods still have the filler dispersed mainly within the bulk phase of the polymer melt during melt blending. In subsequent processing (e.g., injection molding, extrusion), strong shear and elongational flows can disrupt the already formed fragile conductive network, resulting in conductive path breakage and poor product performance reproducibility. In addition, too much compatibilizer may introduce polar interfaces, which adversely affect the crystallization behavior and long-term thermal stability of the polypropylene itself. A further problem is that the prior art concepts are mostly limited to optimizing the homogeneous dispersion of the bulk phase of the filler in the melt state, but neglecting the strong correlation between the final properties of the composite and the history of the processing. On the premise of not obviously damaging the inherent excellent processing fluidity and mechanical toughness of polypropylene, a stable conductive network structure which can self-organize in the processing process and can effectively resist shearing damage is constructed, so that the method is a core contradiction which cannot be well solved by the prior art. This requires collaborative innovation from multiple dimensions of filler spatial distribution design, precise regulation of interface interactions, and timing matching of processing processes, rather than simple component superposition or local improvement. Disclosure of Invention In view of the above, the invention aims to provide a conductive polypropylene composite material and a preparation method thereof, so as to solve the problems that the processing fluidity is obviously reduced due to the fact that the existing conductive polypropylene composite material depends on the uniform dispersion of a bulk phase of a high-content conductive filler in a melt, a fragile conductive network is easily damaged by shearing force in the forming process, and low resistivity, excellent processing property and mechanical toughness are difficult to be achieved. Based on the above purpose, the invention provides a preparation method of a conductive polypropylene composite material, which comprises the following steps: (1) Preparing polypropylene powder with the particle size of 75-150 mu m; (2) Carrying out solid-phase pre-coating mixing on polypropylene powder, stearic acid, carboxylated multiwall carbon