Concentrated conductive black master batch and preparation method thereof

Abstract

The invention discloses a concentrated conductive black master batch and a preparation method thereof, and belongs to the technical field of conductive plastics, the concentrated conductive black master batch comprises the following components by mass percentage: a conductive filler, carrier resin, an auxiliary agent and a double-chamber microcapsule, the double-chamber microcapsule comprises: an outer shell material: polyurea (PUA); the inner part diaphragm is a polylactic acid (PLA) and polycaprolactone (PCL) composite membrane; the first chamber is used for packaging epoxy resin and microencapsulated dicyandiamide; and the second chamber is used for packaging liquid metal gallium indium alloy and spraying benzotriazole (BTA). Through the compounding design of the double-chamber microcapsules and the conductive filler, the cooperation of double self-repairing and high conductivity is realized, liquid metal is heated to flow to repair a conductive path during mechanical damage, epoxy resin curing is triggered by chemical corrosion to repair strength, and a three-dimensional conductive network is constructed by carbon black / carbon nanotubes.

Description

Technical Field

[0001] This invention relates to the field of conductive plastics technology, specifically to a concentrated conductive black masterbatch and its preparation method. Background Technology

[0002] Currently, conductive plastics are increasingly widely used in electronics, automobiles, packaging and other fields, but they still have significant drawbacks in practical use:

[0003] The contradiction between conductivity and self-healing function

[0004] Traditional conductive masterbatches rely heavily on fillers such as carbon black and metal powders, requiring high addition levels (>20%) to form an effective conductive network, leading to deterioration of the material's mechanical properties. While introducing liquid metals or carbon nanotubes can lower the percolation threshold, a single conductive component struggles to balance high conductivity and stability, and is prone to conductive pathway breakage under mechanical damage or corrosive environments, lacking self-healing capabilities. Existing self-healing technologies are mostly based on a single mechanism (such as thermally triggered polymer chain flow or microencapsulated repair agents), capable of repairing only mechanical cracks or localized corrosion, and unable to address complex, multi-faceted damage.

[0005] Limitations of Microcapsule Design and Processing

[0006] In existing single-chamber microcapsule encapsulation of repair agents (such as epoxy resin), the release of the repair agent is uncontrollable and easily interferes with conductive components. Furthermore, microcapsules encapsulating liquid metals often rupture prematurely at plastic processing temperatures (>120°C) due to insufficient temperature resistance of the shell material, leading to the deactivation of the active material. In addition, traditional microcapsules struggle to achieve partitioned encapsulation and synergistic response of multiple repair agents, limiting their multifunctional applications.

[0007] Environmental tolerance and safety issues

[0008] Liquid metals (such as gallium-indium alloys) are easily oxidized to form an insulating oxide layer, requiring the addition of antioxidants. However, conventional antioxidants (such as organophosphates) are prone to migration and precipitation, reducing long-term stability. Microcapsule shells often use non-degradable petroleum-based polymers (such as polyvinyl alcohol), posing a risk of environmental residue. Furthermore, existing conductive masterbatches are prone to filler agglomeration or matrix degradation in high-temperature or corrosive environments, leading to a sharp decline in performance. Summary of the Invention

[0009] The present invention aims to provide a concentrated conductive black masterbatch and its preparation method. This concentrated conductive black masterbatch and its preparation method have dual self-healing functions, significantly improving material reliability. For mechanical damage repair, liquid gallium-indium alloy (melting point 15.7℃) is encapsulated in dual-chamber microcapsules. Under heat (e.g., 80℃) or mechanical stress, the separator membrane (PLA / PCL) ruptures, releasing the liquid metal, which quickly fills the crack and restores the conductive path, achieving an initial repair efficiency of over 92%. For chemical corrosion repair, the encapsulation design of epoxy resin and microencapsulated dicyandiamide in the first chamber triggers a curing reaction when the crack is exposed to moisture or a corrosive environment, restoring the material's structural strength. The secondary repair efficiency reaches 85%. Synergistic effect: the two repair mechanisms independently respond to different damage types, significantly extending the material's service life under complex environments (e.g., humidity, salt spray, mechanical fatigue). Optimized conductive network: the composite of carbon black (high specific surface area) and carbon nanotubes (high aspect ratio) (mass ratio 2:1) forms a three-dimensional interpenetrating conductive network with a volume resistivity as low as 10. 3 With a conductivity of Ω·cm, superior to traditional masterbatches with single fillers, the directional arrangement enhances conductivity. Annealing (80–100℃) promotes the orderly arrangement of conductive fillers in the carrier resin, further reducing the percolation threshold and ensuring high conductivity at low addition levels (3%–8%). Mild processing conditions are achieved, with twin-screw extrusion temperatures (120–160℃) far lower than the PLA decomposition temperature (above 230℃). The microcapsule shell (polyurea) and separator (PLA / PCL) remain intact during processing, preventing premature release of active substances. The masterbatch is highly adaptable, directly melt-blending with PE, PP, TPU, and other substrates, suitable for conventional plastic processing technologies such as injection molding and extrusion, without requiring modifications to existing production lines. It is also suitable for biodegradable applications, as the separator uses a composite of PLA (biodegradable) and PCL (biocompatible), reducing the environmental impact of microcapsule residues. Toxicity control is ensured by a benzotriazole (BTA) coating (0.3%–0.8%) that inhibits liquid metal oxidation and prevents the release of heavy metal ions, complying with RoHS standards.

[0010] To achieve the above effects, the present invention provides the following technical solution: a concentrated conductive black masterbatch, comprising the following components by mass percentage:

[0011] Conductive filler: 15% to 40%, wherein the conductive filler is one or a mixture of carbon black and carbon nanotubes;

[0012] Carrier resin: 50% to 70%, wherein the carrier resin is polyethylene (PE), polypropylene (PP) or thermoplastic polyurethane (TPU);

[0013] Additives: 1%–5%, including dispersants, coupling agents, and antioxidants;

[0014] Dual-chamber microcapsules: 5%–12%, wherein the dual-chamber microcapsules comprise:

[0015] Outer shell material: polyurea (PUA), with a thickness of 2-5 μm;

[0016] Internal separator membrane: a composite membrane of polylactic acid (PLA) and polycaprolactone (PCL), with a thickness of 0.5–1 μm;

[0017] First chamber: Encapsulated with epoxy resin and microencapsulated dicyandiamide in a mass ratio of (5:1) to (10:1);

[0018] Second chamber: encapsulates liquid metal gallium-indium alloy and is coated with benzotriazole (BTA).

[0019] Furthermore, the mass ratio of carbon black to carbon nanotubes in the conductive filler is (2:1) to (1:1), and the carbon black is acetylene black with a specific surface area ≥800 m². 2 / g, carbon nanotubes have a multi-walled structure and an aspect ratio ≥500.

[0020] Furthermore, the particle size of the dual-chamber microcapsules is 50-150 μm, and the amount of benzotriazole (BTA) antioxidant layer sprayed on the surface of the outer shell material is 0.3%-0.8% of the shell material weight.

[0021] Furthermore, the internal separator is a double-layer composite membrane of polylactic acid (PLA) and polycaprolactone (PCL), with the PLA layer accounting for 60% to 80% of the thickness and the PCL layer accounting for 20% to 40% of the thickness.

[0022] Furthermore, the mixing ratio of gallium to indium in the liquid gallium-indium alloy is 75.5:24.5, and the melting point of the liquid gallium-indium alloy is 15.7°C.

[0023] A method for preparing concentrated conductive black masterbatch, applied to any one of the concentrated conductive black masterbatches described above, includes the following steps:

[0024] S1. Preparation of dual-chamber microcapsules: W / O / W dual emulsion droplets are generated using a microfluidic chip. The inner aqueous phase is a liquid gallium indium alloy, the middle oil phase is epoxy resin and microencapsulated dicyandiamide, and the outer aqueous phase contains polyurea prepolymer. The shell is formed by interfacial polymerization at 40-50℃, and a PLA / PCL composite separator is electrostatically sprayed.

[0025] S2. Melt blending of masterbatch: Each component is added to a twin-screw extruder, and then extruded, granulated, and annealed.

[0026] Furthermore, according to the operating steps in S1, the controlled processing temperature of the twin-screw extruder is 120-160℃, the screw speed is 100-200 r / min, and the vacuum degassing pressure is -0.08--0.1 MPa.

[0027] Furthermore, according to the operation steps in S1, the channel diameter of the microfluidic chip is 200-500 μm, and the emulsion droplet generation frequency is 10-50 Hz.

[0028] Furthermore, according to the operation steps in S2, the annealing process involves heat-treating the masterbatch at 80-100°C for 2-4 hours to promote the directional arrangement of the conductive filler network.

[0029] Furthermore, according to the operation steps in S1-S2, conductive plastic products with dual self-healing functions are prepared, wherein the amount of masterbatch added is 3% to 8% of the substrate mass.

[0030] This invention provides a concentrated conductive black masterbatch and its preparation method, which has the following beneficial effects:

[0031] (1) Dual self-healing function significantly improves material reliability

[0032] Mechanical damage repair: Liquid metal gallium indium alloy (melting point 15.7℃) is encapsulated in dual-chamber microcapsules. Under heat (e.g. 80℃) or mechanical stress, the separator membrane (PLA / PCL) ruptures to release the liquid metal, which quickly fills the crack and restores the conductive path. The initial repair efficiency is over 92%.

[0033] Chemical corrosion repair: The encapsulation design of epoxy resin and microencapsulated dicyandiamide in the first chamber can trigger a curing reaction when the crack is exposed to moisture or a corrosive environment, repairing the structural strength of the material and achieving a secondary repair efficiency of 85%.

[0034] Synergistic effect: The two repair mechanisms respond independently to different damage types, significantly extending the service life of materials in complex environments (such as humidity, salt spray, and mechanical fatigue).

[0035] (2) High conductivity and stability

[0036] Conductive network optimization: A composite of carbon black (high specific surface area) and carbon nanotubes (high aspect ratio) (mass ratio 2:1) forms a three-dimensional interpenetrating conductive network with a volume resistivity as low as 10. 3 Ω·cm, superior to traditional masterbatches with single fillers.

[0037] Directional arrangement reinforcement: Annealing treatment (80-100℃) promotes the orderly arrangement of conductive fillers in the carrier resin, further reduces the percolation threshold, and ensures high conductivity at low addition levels (3%-8%).

[0038] (3) Processing compatibility and thermal stability

[0039] Mild processing conditions: The twin-screw extrusion temperature (120-160℃) is much lower than the PLA decomposition temperature (above 230℃), and the microcapsule shell (polyurea) and separator membrane (PLA / PCL) remain intact during processing, avoiding premature release of active substances.

[0040] Process adaptability: The masterbatch can be directly melt-blended with substrates such as PE, PP, and TPU, and is suitable for conventional plastic processing technologies such as injection molding and extrusion, without the need to modify existing production lines.

[0041] (4) Environmental protection and safety

[0042] Application of biodegradable materials: The separator membrane is made of PLA (biodegradable) and PCL (biocompatible) composite to reduce the environmental impact of microcapsule residues.

[0043] Toxicity control: The benzotriazole (BTA) spray coating (0.3%–0.8%) inhibits the oxidation of liquid metals and prevents the release of heavy metal ions, thus complying with RoHS standards.

[0044] (5) Multifunctional application scenarios

[0045] In the field of flexible electronics: the fluidity of liquid metals makes them suitable for flexible circuits and self-healing conductive layers for stretchable sensors.

[0046] In the field of industrial protection: the repair capabilities of epoxy resin can enhance the corrosion resistance of antistatic packaging and pipe linings.

[0047] Wide temperature range applicability: The masterbatch maintains stable performance within a temperature range of -20℃ to 120℃, meeting the requirements of extreme environments such as automobiles and outdoor equipment. Attached Figure Description

[0048] Figure 1 This is a schematic flowchart of a concentrated conductive black masterbatch and its preparation method according to the present invention. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0050] This invention provides a technical solution:

[0051] See also Figure 1 Example 1: A concentrated conductive black masterbatch, comprising the following components by mass percentage:

[0052] Conductive filler: 30% (carbon black and carbon nanotubes are mixed at a mass ratio of 2:1, wherein the carbon black is acetylene black with a specific surface area ≥800m²). 2 / g. Carbon nanotubes have a multi-walled structure with an aspect ratio ≥500).

[0053] Carrier resin: 65% (thermoplastic polyurethane TPU is selected).

[0054] Additives: 3% (containing dispersant polyethylene glycol, coupling agent silane KH550, and antioxidant 1010, in a mass ratio of 2:1:1).

[0055] Dual-chamber microcapsules: 10%, with the following structure:

[0056] Outer shell material: Polyurea (PUA) shell, 3μm thick.

[0057] Internal separator: PLA and PCL bilayer composite membrane (PLA layer accounts for 70%, thickness 0.7μm; PCL layer accounts for 30%, thickness 0.3μm).

[0058] First chamber: Encapsulated with epoxy resin and microencapsulated dicyandiamide in a mass ratio of 8:1.

[0059] Second chamber: encapsulates liquid metal gallium-indium alloy (gallium:indium = 75.5:24.5, melting point 15.7℃), and the surface is sprayed with benzotriazole (BTA), with the spraying amount being 0.5% of the shell material weight.

[0060] A method for preparing concentrated conductive black masterbatch, applied to any one of the concentrated conductive black masterbatches described above, includes the following steps:

[0061] S1: Preparation of dual-chamber microcapsules

[0062] W / O / W dual emulsion droplets were generated using a microfluidic chip (channel diameter 350 μm, emulsion droplet generation frequency 30 Hz).

[0063] Inner aqueous phase: liquid gallium-indium alloy (dispersed ultrasonically to a particle size ≤10μm).

[0064] Intermediate oil phase: epoxy resin E51 and microencapsulated dicyandiamide (particle size 5μm).

[0065] Outer aqueous phase: Contains polyurea prepolymer (isocyanate to amine monomer molar ratio 1:1),

[0066] An interfacial polymerization reaction was carried out at 45°C for 2 hours to form a polyurea shell.

[0067] PLA / PCL layers are laminated onto the surface of the separator membrane using an electrostatic spraying process (PLA melting temperature 170℃, PCL melting temperature 60℃).

[0068] S2: Masterbatch melt blending

[0069] The conductive filler, carrier resin, additives, and dual-chamber microcapsules are added to a twin-screw extruder. Process parameters:

[0070] Processing temperature: 150℃ (temperature gradient from zone 1 to zone 5: 120℃→160℃).

[0071] Screw speed: 150 r / min.

[0072] Vacuum degassing pressure: -0.09MPa.

[0073] After extrusion granulation, the masterbatch is annealed: heat-treated at 95℃ for 3 hours to promote the formation of a three-dimensional conductive network of carbon black / carbon nanotubes.

[0074] Performance testing: The masterbatch from this embodiment was blended with polypropylene (PP) substrate at a dosage of 5% and injection molded to obtain conductive plastic samples. The test results are as follows: Conductivity: Volume resistivity ≤10 3 Ω·cm (ASTM D257). Self-healing efficiency: After the first mechanical damage (crack width 50μm), heating to 80℃ and maintaining for 10 minutes, liquid metal is released to fill the crack, with a conductivity recovery rate of 92%. After secondary chemical corrosion (immersion in 5% NaCl solution for 24 hours), dicyandiamide triggers epoxy resin curing, with a strength recovery rate of 85%. Thermal stability: The masterbatch showed no microcapsule rupture after being held at 160℃ for 20 minutes (TGA verification). Application effect: This masterbatch is suitable for preparing antistatic packaging, flexible sensors, and other plastic products with dual self-healing functions, and can be used stably for a long time in environments ranging from -20℃ to 120℃.

[0075] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A concentrated conductive black masterbatch, characterized in that, The components include the following percentages by mass: Conductive filler: 15% to 40%, wherein the conductive filler is one or a mixture of carbon black and carbon nanotubes; Carrier resin: 50% to 70%, wherein the carrier resin is polyethylene (PE), polypropylene (PP) or thermoplastic polyurethane (TPU); Additives: 1%–5%, including dispersants, coupling agents, and antioxidants; Dual-chamber microcapsules: 5%–12%, wherein the dual-chamber microcapsules comprise: Outer shell material: polyurea (PUA), with a thickness of 2-5 μm; Internal separator membrane: a composite membrane of polylactic acid (PLA) and polycaprolactone (PCL), with a thickness of 0.5–1 μm; First chamber: Encapsulated with epoxy resin and microencapsulated dicyandiamide in a mass ratio of (5:1) to (10:1); Second chamber: encapsulates liquid metal gallium-indium alloy and is coated with benzotriazole (BTA).

2. The concentrated conductive black masterbatch according to claim 1, characterized in that, The mass ratio of carbon black to carbon nanotubes in the conductive filler is (2:1) to (1:1), and the carbon black is acetylene black with a specific surface area ≥800 m². 2 / g, carbon nanotubes have a multi-walled structure and an aspect ratio ≥500.

3. The concentrated conductive black masterbatch according to claim 1, characterized in that, The particle size of the dual-chamber microcapsules is 50-150 μm, and the benzotriazole (BTA) antioxidant layer sprayed on the surface of the outer shell material is 0.3%-0.8% of the shell material weight.

4. The concentrated conductive black masterbatch according to claim 1, characterized in that, The internal separator is a double-layer composite membrane of polylactic acid (PLA) and polycaprolactone (PCL), with the PLA layer accounting for 60% to 80% of the thickness and the PCL layer accounting for 20% to 40% of the thickness.

5. The concentrated conductive black masterbatch according to claim 1, characterized in that, The mixing ratio of gallium to indium in the liquid gallium-indium alloy is 75.5:24.5, and the melting point of the liquid gallium-indium alloy is 15.7℃.

6. A method for preparing concentrated conductive black masterbatch, characterized in that, The application of a concentrated conductive black masterbatch according to any one of claims 1-5 includes the following steps: S1. Preparation of dual-chamber microcapsules: W / O / W dual emulsion droplets are generated using a microfluidic chip. The inner aqueous phase is a liquid gallium indium alloy, the middle oil phase is epoxy resin and microencapsulated dicyandiamide, and the outer aqueous phase contains polyurea prepolymer. The shell is formed by interfacial polymerization at 40-50℃, and a PLA / PCL composite separator is electrostatically sprayed. S2. Melt blending of masterbatch: Each component is added to a twin-screw extruder, and then extruded, granulated, and annealed.

7. The preparation process of a concentrated conductive black masterbatch according to claim 6, characterized in that, The process includes the following steps: According to the operating steps in S1, the controlled processing temperature of the twin-screw extruder is 120-160℃, the screw speed is 100-200 r / min, and the vacuum degassing pressure is -0.08--0.1 MPa.

8. The preparation process of a concentrated conductive black masterbatch according to claim 6, characterized in that, Includes the following steps: According to the operation steps in S1, the channel diameter of the microfluidic chip is 200-500 μm, and the emulsion droplet generation frequency is 10-50 Hz.

9. The preparation process of a concentrated conductive black masterbatch according to claim 6, characterized in that, The process includes the following steps: According to the operation steps in S2, the annealing process involves heat-treating the masterbatch at 80-100°C for 2-4 hours to promote the directional arrangement of the conductive filler network.

10. The preparation process of a concentrated conductive black masterbatch according to claim 6, characterized in that, Includes the following steps: According to the operation steps in S1-S2, conductive plastic products with dual self-healing functions are prepared, wherein the amount of masterbatch added is 3% to 8% of the mass of the substrate.

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