A high-flow conductive polypropylene composite material and its preparation method

Abstract

The present invention belongs to the technical field of polypropylene composite materials, and relates to a high-flow conductive polypropylene composite material and a preparation method thereof. The present invention provides a high-flow conductive polypropylene composite material, which, by mass, comprises: 100 parts of polypropylene, 20 to 40 parts of conductive filler, 1 to 3 parts of nucleating agent, 10 to 20 parts of polyethylene wax, 2 to 10 parts of silicone powder, 7 to 15 parts of maleic anhydride, 10 to 20 parts of tannic acid, and 8 to 16 parts of aminopropyltriethoxysilane. The present invention uses tannic acid and aminopropyltriethoxysilane as interfacial compatibilizers, and in cooperation with silicone powder, can greatly improve the interfacial compatibility between the conductive filler and polypropylene, taking into account high conductivity while improving the fluidity and yield of the conductive polypropylene composite material.

Description

Technical Field

[0001] The present invention belongs to the technical field of polypropylene composites, and relates to a high-flow conductive polypropylene composite material and a preparation method thereof. Background Art

[0002] Conductive polypropylene composite materials are functional polymer materials that achieve electrical conductivity by adding conductive fillers to a polypropylene (PP) matrix. These materials combine the characteristics of polypropylene such as light weight, chemical corrosion resistance, and easy processing, as well as electrical conductivity, and thus have broad application prospects in fields such as antistatic packaging, electromagnetic shielding, electronic components, and the automotive industry. Common conductive fillers include carbon nanotubes (CNTs), metal powders (such as silver powder, copper powder, nickel powder), conductive carbon black (CB), graphene, etc. Their conduction mechanism mainly depends on the formation of a percolation network of the fillers in the matrix, that is, when the filler addition amount reaches the percolation threshold, the resistivity of the material decreases significantly.

[0003] However, in the prior art, there is a significant contradiction between the electrical conductivity and processing fluidity of conductive polypropylene composite materials. To achieve good electrical conductivity (such as volume resistivity ≤ 10 6 Ω·cm), a relatively high amount of conductive filler is usually required. For example, 15 - 30 wt% of conductive carbon black needs to be added, 20 - 40 wt% of metal powder needs to be added, and although carbon nanotubes can reduce the addition amount due to their high aspect ratio (usually 1 - 5 wt%), dispersion technology is still required to ensure the integrity of the network structure. The high filling amount will cause the following problems: First, the introduction of conductive fillers will significantly increase the melt viscosity of the composite material, reduce its melt flow index (MFI), resulting in poor fluidity during processing such as injection molding and extrusion, and problems such as insufficient mold filling and surface defects are likely to occur in the products; Second, the agglomeration phenomenon of excessive fillers will further deteriorate the material homogeneity, affecting the mechanical properties (such as the impact strength and tensile strength decrease), resulting in a decrease in the finished product rate; In addition, the high density of metal fillers may cause an increase in the material density, and the hydrophobicity of carbon-based fillers may lead to insufficient interfacial compatibility with the polypropylene matrix. Summary of the Invention

[0004] The purpose of the present invention is to solve the technical problem that when preparing conductive polypropylene composite materials, in order to ensure better electrical conductivity, a large amount of conductive fillers are added, resulting in a decrease in fluidity, so that compatibilizers or lubricants have to be added to improve its physical properties such as fluidity, but these methods sacrifice the electrical conductivity, resulting in the inability to balance high fluidity and high electrical conductivity. In view of this, the present invention provides a high-flow conductive polypropylene composite material and a preparation method thereof to solve this need in the field.

[0005] On the one hand, the present invention relates to a highly flowable conductive polypropylene composite material, which, by mass parts, comprises: 100 parts of polypropylene, 20 - 40 parts of conductive filler, 1 - 3 parts of nucleating agent, 10 - 20 parts of polyethylene wax, 2 - 10 parts of silicone powder, 7 - 15 parts of maleic anhydride, 10 - 20 parts of tannic acid, and 8 - 16 parts of aminopropyltriethoxysilane.

[0006] Further, in the highly flowable conductive polypropylene composite material provided by the present invention, the conductive filler is selected from at least one of carbon nanotubes, metal powder, and conductive carbon black.

[0007] Further, in the highly flowable conductive polypropylene composite material provided by the present invention, the nucleating agent is selected from at least one of α-crystalline nucleating agent and β-crystalline nucleating agent.

[0008] Further, in the highly flowable conductive polypropylene composite material provided by the present invention, by mass parts, it further comprises 1 - 3 parts of additives.

[0009] Further, in the highly flowable conductive polypropylene composite material provided by the present invention, the additives are antioxidant and / or toughening agent.

[0010] Further, in the highly flowable conductive polypropylene composite material provided by the present invention, the antioxidant is selected from at least one of antioxidant 1070, antioxidant 1076, and antioxidant 168.

[0011] Further, in the highly flowable conductive polypropylene composite material provided by the present invention, the toughening agent is selected from at least one of POE8400, POE 8480, and POE 8150.

[0012] On the other hand, the present invention relates to a preparation method of a highly flowable conductive polypropylene composite material, which comprises: taking polypropylene, conductive filler, nucleating agent, polyethylene wax, silicone powder, maleic anhydride, tannic acid, and aminopropyltriethoxysilane as raw materials, mixing them and then performing melt granulation to obtain the highly flowable conductive polypropylene composite material.

[0013] Further, in the preparation method provided by the present invention, the temperature of the melt granulation is 200 - 230 °C.

[0014] Further, in the preparation method provided by the present invention, the screw speed of the melt granulation is 200 - 400 r / min.

[0015] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages:

[0016] The present invention solves the problem of incompatibility between conductivity and fluidity in conductive polypropylene composites by introducing tannic acid and aminopropyltriethoxysilane as interfacial compatibilizers and combining with the lubricating effect of silicone powder. The polyphenolic hydroxyl structure of tannic acid can be adsorbed on the surface of conductive fillers (such as carbon black), reducing their surface energy and inhibiting aggregation, while aminopropyltriethoxysilane forms chemical bonding with the polypropylene matrix through the silanol groups generated by hydrolysis, enhancing the interfacial bonding force. Silicone powder further optimizes fluidity by reducing the melt viscosity. The synergistic effect of the three enables the formation of a continuous conductive network by conductive fillers at a lower addition amount (the percolation threshold is reduced), while reducing the melt flow resistance. Compared with the prior art, the present invention significantly improves the melt flow rate (MFR≥35 g / 10min) while maintaining high conductivity (resistivity≤10 5 Ω·cm), and improves the mechanical properties (the tensile modulus is increased by about 30%). In addition, the process parameters (melting temperature 200~230℃, screw speed 40~100 r / min) match the interfacial modification requirements, ensuring material uniformity and processing efficiency. This technical solution breaks through the bottleneck of the decrease in fluidity caused by a high filler amount in traditional conductive composites through the synergistic effect of interfacial compatibilizers, and is applicable to fields with strict requirements for conductivity, processability, and mechanical properties (such as precision electronic components, antistatic packaging). Brief Description of the Drawings

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0018] Figure 1 It is a physical diagram of the high-flow conductive polypropylene composite material prepared by the present invention. Detailed Embodiments

[0019] Next, the technical solutions of the present invention will be described in conjunction with the embodiments. However, the present invention is not limited to the following embodiments. The experimental methods and detection methods described in each embodiment are all conventional methods unless otherwise specified; the reagents and materials described are all commercially available unless otherwise specified. The % in the following embodiments is the mass percentage unless otherwise specified. The ratios in the following embodiments are all mass ratios unless otherwise specified.

[0020] The sources of the raw materials used in the following embodiments are as follows:

[0021] Polypropylene, model 7760H, was purchased from Yanshan Petrochemical.

[0022] Silicone powder, model number MB50, was purchased from Dow Chemical Company.

[0023] Maleic anhydride, model number FR-100A, was purchased from Dongguan Xingyuan Chemical Co., Ltd.

[0024] The antioxidant and toughening agent were purchased from Dow.

[0025] Preparation Example

[0026] Each component was uniformly mixed by a pulverizer according to the formula described in Table 1, and melt-blended with polypropylene in an open mill at 220 °C for 15 min. The roller speeds of the open mill were set at 25 r / min and 15 r / min. Then, granulation was carried out by a twin-screw extruder at a granulation temperature of 230 °C and a screw speed of about 300 r / min. Finally, after the pellets were dried, they were injection-molded into standard specimens. The injection temperature during injection molding was 230 °C and the pressure was 40 MPa.

[0027] Table 1: Formulation of Conductive Polypropylene Composite

[0028]

[0029] Performance Test:

[0030] Resistivity measurement was carried out according to GB / T 31838.3-2019. The charging voltage and charging time of the high resistance meter were set at 500 V and 15 s, and the temperature and humidity were maintained at (20±2) °C and (65±5)% during the test.

[0031] Tensile property test was carried out according to GB / T 1040.1-2018. The gauge length was 50 mm, the tensile rate was 50 mm / min, and 5 specimens were tested in each group.

[0032] Flexural property test was carried out according to GB / T 1449-2005. The specimen size was 80 mm×10 mm×5 mm, the span was 64 mm, the test speed was 50 mm / min, and 5 specimens were tested in each group.

[0033] Torque rheology test was used to test the rheological properties of the composite material with a torque rheometer. Each time about 50 g of material was added, the rotor speed was set at 60 r / min, and the experiment was a thermal fusion experiment with the temperature set at 190 °C.

[0034] MFR test was carried out to test the MFR of the composite material with a melt indexer at a temperature of 230 °C and a pressure of 5 kg.

[0035] Table 2: Performance Test Results

[0036]

[0037] As can be seen from the results in Table 2, high conductivity requires a high filler content, but this will lead to an increase in melt viscosity and a decrease in fluidity. In the present invention, tannic acid and aminopropyltriethoxysilane are used as interfacial compatibilizers, which, in cooperation with silicone powder, significantly optimize the dispersion of conductive fillers (such as carbon black, which is a conductive filler with relatively poor conductivity). When the content of the conductive filler is low (20 - 40 parts), the resistivity can still be controlled at 10 3 ~10 5 Ω·cm level (generally, 10 8 Ω·cm is considered conductive, and 10 3 ~10 5 Ω·cm is considered highly conductive). At the same time, the MFR is as high as 35.6 - 39.7 g / 10 min, achieving a balance between conductivity and fluidity. Tannic acid and aminopropyltriethoxysilane acting as interfacial compatibilizers together reduce filler agglomeration, enhance the interfacial bonding between the filler and the matrix, and avoid the deterioration of mechanical properties caused by excessive fillers.

[0038] As described above, the basic principles, main features, and advantages of the present invention are preferably described. The above embodiments and the description are only for describing the preferred embodiments of the present invention. The present invention is not limited by the above embodiments. Without departing from the spirit and scope of the present invention, various changes and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the present invention.

Claims

1. A highly flowable conductive polypropylene composite material, characterized in that, By mass parts, it includes: 100 parts of polypropylene, 20 - 40 parts of conductive filler, 1 - 3 parts of nucleating agent, 10 - 20 parts of polyethylene wax, 2 - 10 parts of silicone powder, 7 - 15 parts of maleic anhydride, 10 - 20 parts of tannic acid, and 8 - 16 parts of aminopropyltriethoxysilane; The conductive filler is selected from at least one of carbon nanotubes, metal powder, and conductive carbon black; The nucleating agent is selected from at least one of α - crystal form nucleating agent and β - crystal form nucleating agent; By mass parts, it further includes 1 - 3 parts of additive; The additive is antioxidant and toughening agent; The resistivity of the high-flow conductive polypropylene composite material is ≤ 10 5 Ω·cm, and the melt flow rate MFR ≥ 35 g / 10min.

2. The high-flow conductive polypropylene composite material according to claim 1, characterized in that The antioxidant is at least one of antioxidant 1070, antioxidant 1076, and antioxidant 168.

3. The highly flowable conductive polypropylene composite material according to claim 1, wherein The toughening agent is at least one of POE8400, POE 8480, and POE 8150.

4. A method for preparing the high-flow conductive polypropylene composite material according to any one of claims 1 to 3, characterized in that, It includes: Taking polypropylene, conductive filler, nucleating agent, polyethylene wax, silicone powder, maleic anhydride, tannic acid, and aminopropyltriethoxysilane as raw materials, after mixing, melt granulation is carried out to obtain the high - flow conductive polypropylene composite material.

5. The preparation method of the high-flow conductive polypropylene composite material according to claim 4, characterized in that, The temperature of the melt granulation is 200 - 230 °C.

6. The preparation method of the high-flow conductive polypropylene composite material according to claim 4, characterized in that The screw rotation speed of the melt granulation is 200 - 400 r / min.

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